INIS-SD-12B SD0000053
BROMOSUBSTITUTED ARYL HYDROXAMIC ACIDS AND THEIR ANALYTICAL APPLICATION TOWARDS SOME TRANSITION METALS.
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1997 PLEASE BE AWARE THAT ALL OF THE MISSING PAGES IN THIS DOCUMENT WERE ORIGINALLY BLANK TO AW PARENTS ****** TO MY CHILDERN ****** TO MY WIFE ******* TO MY BROTHERS AND SISTERS**** A CKNO WLEDGEMENT
I would like to express my deepest thanks and gratitude to my supervisor Dr. Hassan Abdelaziz Abdalla for his directions, invaluable advice, encouragement and guidance throughout the course of this study. Thanks are also extended to the staff of Chemistry Department for their help and the Department of Chemistry where this investigation has been carried out, for laboratory facilities and valuable assistance in the use of various equipments. My greateful thanks to my brothers and friends for their assistance and support during the course of my study. Thanks are due to miss Hameeda Elamin for typing this thesis. Finally I would like to thank University of Khartoum for providing the scholarship. ABSTRACT Four aryl substituted hydroxamic acids were prepared: N-phenyl-N-p- bromobenzohydroxamic acid, N-phenyl-N-o-bromobenzohydroxamic acid, p-melhyl-N-phenyl-N-p-bromobenzohydroxamic acid and P-rnethyl-N-phenyl-N- o-bromobenzohydroxamic acid by the reaction of [3-phenylhydroxylamine and p-methyl-P phenylhydroxylamine with the corresponding acid chloride. The acids were identified by their melting points, elemental analysis (nitrogen and bromine contents), infrared and ultraviolet absorption in chloroform, as well as reactions towards acidic solutions of vanadium (V) and iron (III) to give violet and blood- red coloured complexes in the chloroform layer respectively. The extractability of these acids towards chromium (VI), molybdenum (VI), iron (III), vanadium (V), copper (II) and cobalt (II) was investigated . N-phenyl-N-p-bromobenzohydroxamic acid has a maximum extraction for chromium (VI) 96.00 % at IM H2SO4, molybdenum (VI) 87.00 % at pH 1, iron (III) 73.90% at pH 4, vanadium (V) 93.00% at pH 1, cobalt (II) 83.10 at pH 8 and copper (II) 93.80% at pH 6. N-phenyl-N-o-bromobenzohydroxamic acid has a maximum extraction for chromium (VI) 97.00% at IM H2SO4, molybdenum (VI) 92.70% at pH 1, iron (III) 71.20% at pi I 4, vanadium (V) 90.00% at pH 1, cobalt (II) 54.70% at pH 7 and copper (II) 86.50% at pH 5. P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid has a maximum extraction for chromium (VI) 98.70% at IM H2SO4, molybdenum (VI) 74.00% at pH 1, iron (III) 69.60% at pH 5, vanadium (V) 76.00% at pH 1, cobalt (II) 51.20% at pi I 8 and copper (II) 82.20% at pH 5. P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid has a maximum extraction for chromium (VI) 51.00% at IM H2SO4, molybdenum (VI) 84.70% at pi 1 I , iron (III) 66.00% at pH 4, vanadium (V) 88.00% at pH 1, cobalt (II) 50.00% at pi I 7 and copper (II) 78.6% at pH 6.
Twenty four of hydroxamic acids complexes of Cr ( VI), Mo (VI), V (V), Fe (III), Co (II) and Cu (II) were prepared by the reaction of these acids with the six metals at different medium. The ratio of the metal to ligand was determined by the continuous variation method and elemental analysis of these complexes. The ratios of Cr (VI), Mo (VI), V(V), Fe (III), Co (II) and Cu (II) were found as follows: 1:2 , 1 : 2, 1 : 1, 1 : I, 1:2 and 1 : 2 respectively. CONTENTS
Title -. - i Dedication
CHAPTER ONE:
Introduction 1 1.1 Analytical Chemistry 1 i -> Methods of Analysis 1 1.2.1 Chemical Methods 1 , 1.2.2 Physicochemical Methods ." 1 1.3 Solvent Extraction 2 1.3.1 Theories of Solvent Extraction 3 1.3.1 .1 Distribution law 3 1.3.1 .2 Distribution Ratio 4 1.3.1 .3. The Percent Extraction (Recovery ) 6 1.3.1 .4. Successive Extraction 7 1.3.2 Solvent Extraction of Metals 7 1.3.2 .1 Ion Association Complexes 7 1.3.2 -) Metal Chelates 7 1.3.2 .3. Extraction Process 8 1.3.2 .4 The Seperation Efficiency of Metal Chelates 11 1.4. Analytical Seperations 12 1.4.1 Multiple Batch Extraction 12 1.5. Organic Reagents in Analytical Chemistry 14 1.6. Some Applications of Organic Reagents in Analytical Chemistry 15 1.6.1 Gravimetric Analysis 15 1.6.2 Complexing Agents 15 1.6.3 Colourimetric Analysis 16 1.7 Hydroxamic Acids 16
via 1.7.1 Structure of Hydroxamic Acids 16 1.7.2 Preparation of Hydroxamic Acids 18 1.7.3 Properties of Hydroxamic Acids 20 1.7.4. Detection of Hydroxamic Acids 20 1.7.5 Acidity of Hydroxamic Acids 21 1.8. Some Applications of Hydroxamic Acids 24 1.8.1 Gravimetric Determination 24 1.8.2 Hydroxamic Acid Resins 25 1.8.3 Spectrophotometric Determinations 26 1.8.3.1 Stripping 28
CHAPTER TWO:
2. EXPERIMENTAL AND RESULTS 35 2.1 Preparation of Hydroxamic Acids 35 2.1.1 Preparation of N-phenyl-N-benzohydroxamic Acid 35 2.1.1.1 Preparation of P-phenylhydroxylamine 36 2.1.1.2 The coupling Reaction Between P-phenylhydroxylamine and Benzoyl chloride 36 2.1.2 Preparation ofN-phenyl-N-p-bromobenzohydroxamic Acid .... 37 2.1.2.1 Preparation of p-bromobenzoyl chloride 38 2.1.2.2. Preparation of (3-phenylhydroxylamine 38 2.1.2.3 The Coupling Reaction Between P-phenylhydroxylamine and p- bromobenzoyl chloride 38 2.1.3 Preparation of N-phenyl-N-o-bromobenzohydroxamic Acid ... 39 2.1.3.1. Preparation of P-phenylhydroxylamine 39 2.1.3.2. Preparation of o-bromobenzoyl chloride 40 2.1.3.3. The Coupling Reaction Between o-bromobenzoyl chloride and |3- phenyihydroxylamine 40 2.1.4. Preparation of p-methyl-N-phenyl-N-p-bromobenzohydroxamic Acid 40 2.1.4.1 Preparation of p-methyl -N-phenyl hydroxylamine 41 2.1.4.2 Preparation of p-bromobenzoyl chloride 41 2.1.4.3 The Coupling Reaction Between p-bromobenzoyl and P-methyl -N- phenylhydroxylamine 42 2.1.5 Preparation of p-methyl-N-phenyl-N-o-bromobenzohydroxamic Acid 42 2.1.5.1 Preparation ofp-methyl -N-phenylhydroxylamine 42 2.1.5.2 Preparation of o-bromobenzoyl chloride 42 2.1.5.3 The Coupling Reaction Between p-methyl-N-phenylhydroxylamine and o-bromobenzoyl chloride 43 2.2. Characterization of the Four Hydroxamic Acids 43 2.2.1 Their Melting Points 43 2.2.2 Characteristic Colour Reaction 44 2.2.3. Elemental Analysis 44 2.2.3.1. Determination of Nitrogen Content 44 2.2.3.2. Determination of Bromine Content 45 2.2.4 Infrared Spectrosocpy 46 2.2.5 Ultra-violet Absorption 47 2.3. Extraction and Colourimetric Determinations of Molybdenum (VI),Chromium (VI) .Iron (III) Vanadium (V), Cobalt (II) and Copper (II) 49 2.3.1. Extraction and Analysis of Chromium (VI) 49 2.3.1.1. Extraction of Chromium (VI) with N-phenyl-N-p-bromobenzo- hydroxamic Acid 50 2.3.1.2. Preparation of Standard (Calibration ) Curve 50 2.3.1.3. Determination of Chromium (VI) in the Aqueous layer 53 2..3.1.4 Determination of Chromium (VI) in the Organic layer 53 2.3.2. Extraction and Analysis of Molybdenum (VI) 60 2.3.2.1 Extraction of Molybdenum (VI) with N-phenyl-N-p-bromobenzohy droxamic Acid 60 2.3.2.2. The Standard (Calibration) Curve - 60 2.3.2.3. The Determination of Molybdenum (VI) in the Aqueous layer 63 2.3.2.4. The Determination of Molybdenum (VI) in the Organic layer 63 2.3.3. Extraction and Analysis of Iron (III) 68. 2.3.3.1 Extraction of Iron (III) with N-phenyl-N-p-bromobenzohy- droxmic Acid 68 2.3.3.2. The Standard (Calibration) Curve 68 2.3.3.3. The Determination of Iron (III) in the Aqueous layer •. 71 2.3.3.4. The Determination o f Iron (III) in the Organic Layer 71 2.3.4. Extraction and Analysis of Vanadium (V) 77 2.3.4.1 Extraction of Vanadium (V) with N-phenyl-N-p-bromobenzohy- droxamic Acid 77 2.3.4.2. The Standard (Calibration) Curve 78 2.3.4.3. The Determination of Vanadium (V) in the Aqueous layer 80 2.3.4.4. The Determination of Vanadium (V) in the Organic layer 80 2.3.5. Extraction and Analysis of Cobalt (II) 86 2.3.5.1 Extraction of Cobalt (II) with N-phenyl-N-p- bromobenzohydroxamic Acid 86 2.3.5.2 The Standard (Calibration ) Curve 86 2.3.5.3. The Determination of Cobalt (II) in the Aqueous Layer 89 2.3.5.4 The Determination of Cobalt (II) in the Organic Layer 89 2.3.6. Extraction and Analysis of Copper (II) 92 2.3.6.1. Extraction of Copper (II) with N-phenyl-N-p- bromobenzohydroxamic Acid 92 2.3.6.2. The standard (Calibration ) Curve 92 2.3.6.3. The Determination of Copper (II) in the Aqueous Layer 97 2.3.6.4. The Detemination of Copper (II) in the Organic Layer 97 2.4. Metal Complexes 102 2.5. Spectrophotometric Studies on M+n - hydroxamic Acids 105 2.5.1. M+n N-phenyl-N-p-bromobenzohydroxamic Acid Complexes... 105 2.5.1.1. Continuous Variation Method 105
CHAPTER THREE:
3. DISCUSSION 137 3.1 Preparation 137 3.2 Identification and Characterization 138 3.2.1. Elemental Analysis 138 3.2.2. Infrared Spectra -. 138 3.2.3. Ultra-violet Spectra 139 3.3. Extraction 139 3.4. Complexes of Hydroxamic Acids 144 3.5. Continuous Variation Method 145
CHAPTER FOUR: 4. REFERENCES 154
XI List of Tables: Table (1) Some hydroxamic acids used for the extraction of some metals 29 Table (2) Melting points of the four hydroxamic acids 44 Table (3) Elemental analysis of the four hydroxamic acids 46 Table (4) Characteristic infrared absorptions of the four hydroxamic acids 47 Table (5) Maximum absorptions of the four hydroxamic acids in chloroform 48 Table (6) Calibration curve for Cr (VI) by diphenylcarbazide method 51 Table (7) Percent extraction of Cr (VI) with 0.5 % w/v N-phenyl- N-p-bromobenzohydroxamic acid 54 Table (8) Percent extraction of Cr (VI) with 0.5 % w/v N-phenyl- N-o-bromobenzohydroxamic acid 55 Table (9) Percent extraction of Cr (VI) with 0.5 % w/v P-methyl N- phenyl- N-p-bromobenzohydroxamic acid 56 Table (10) Percent extraction of Cr (VI) with 0.5 % w/v P-methyl N- phenyl- N-o-bromobenzohydroxamic acid 57 Table (11) The maximum recovery of Cr (VI) with the four hydroxamic acids 57 Table (12) Calibration curve for Mo (VI) by thiocyanate colourimetnc method 61 Table (13) Percent extraction of Mo (VI) with 0.5 % w/v N-phenyl- N-p-bromobenzohydroxamic acid 64 Table (14) Percent extraction of Mo (VI) with 0.5 % w/v N-phenyl- N-o-bromobenzohydroxamic acid 64 Table (15) Percent extraction of Mo(VI) with 0.5 % w/v P-methyl N- phenyl- N-p-bromobenzohydroxamic acid 65 Table (16) Percent extraction of Mo (VI) with 0.5 % w/v P-methyl N- phenyl- N-o-bromobenzohydroxamic acid 65 Table (17) The maximum recovery of Mo (VI) with the four hydroxamic acids 66 Table (18) Calibration curve for Fe (III) by thiocyanate colourimetric method 69 Table (19) Percent extraction of Fe (III) with 0.5 % w/v N-phenyl- N-p-bromobenzohydroxamic acid , 72
Table (20) Percent extraction of Fe (III) with 0.5 % w/v N-phenyl- N-o-bromobenzohydroxamic acid 72
Xll Table (21) Percent extraction of Fe (III) with 0.5 % w/v P-methyl N- phenyl- N-p-bromobenzohydroxamic acid 73 Table (22) Percent extraction of Fe (III) with 0.5 % w/v P-methyl N- phenyl- N-o-bromobenzohydroxamic acid 73 Table (23) The maximum recovery of Fe (III) with the four hydroxamic acid 74 Table (24) Calibration curve for V (V) by N-phenyl-N- benzohydroxamic acid colourimetric method 78. Table (25) Percent extraction of V (V) with 0.5 % w/v N-phenyl- N-p-bromobenzohydroxamic acid 81 Table (26) Percent extraction of V (V ) with 0.5 % w/v N-phenyl- N-o-bromobenzohydroxamic acid 81 Table (27) Percent extraction of V (V ) with 0.5 % w/v P-methyl N- phenyl- N-p-bromobenzohydroxamic acid 82 Table (28) Percent extraction of V (V ) with 0.5 % w/v P-methyl N- phenyl- N-o-bromobenzohydroxamic acid 82 Table (29) The maximum recovery of V (V ) with the four hydroxamic acids 83 Table (30) Calibration curve for Co (II) by colourimetric method.. 87 Table (31) Percent extraction of Co (II) with 0.5 % w/v N-phenyl- N-p-bromobenzohydroxamic acid 90 Table (32) Percent extraction of Co (II) with 0.5 % w/v N-phenyl- N-o-bromobenzohydroxamic acid 90 Table (33) Percent extraction of Co (II) with 0.5 % w/v P-methyl N- phenyl-N-p-bromobenzohydroxamic acid 91 Table (34) Percent extraction of Co (II) with 0.5 % w/v P-methyl N- phenyl- N-o-bromobenzohydroxamic acid 91 Table (35) The maximum recovery of Co (II) with the four hydroxamic acids 92 Table (36) Calibration curve for Cu (II) by sodium diethylditho carbamate colourimetric method 95 Table (37) Percent extraction of Cu (II) with 0.5 % w/v N-phenyl- N-p-bromobenzohydroxamic acid 98 Table (38) Percent extraction of Cu (II) with 0.5 % w/v N-phenyl- N-o-bromobenzohydroxamic acid 98 Table (39) Percent extraction of Cu (II) with 0.5 % w/v P-methyl N- phenyl- N-p-bromobenzohydroxamic acid 99 Table (40) Percent extraction of Cu (II) with 0.5 % w/v P-methyl N- phenyl- N-o-bromobenzohydroxamic acid 99 Table (41) The maximum recovery of Cu (II) with the four hydroxamic acids 100 Table (42) Identification of metal ion complexes of N-phenyl-N-p- bromobenzohydroxamic acid ( L ) 102
XIII Table (43) Identification of metal ion complexes of N-phenyl-N-o- bromobenzohydroxamic acid ( L ) 103 Table (44) Identification of metal ion complexes of P-methyl -N- " phenyl-N-p- bromobenzohydroxamic acid ( L ) 103 Table (45) Identification of metal ion complexes of P-methyl -N- phenyl-N-o-bromobenzohydroxamic acid ( L ) 104 Table (46) Characteristic colours of hydroxamate complexes in chloroform 106 Table (47) Continuous variation method for Cr (VI) -N-phenyl-N-o- bromobenzohydroxamic acid system 107 Table (48) Continuous variation method for Cr (VI) -N-phenyl-N-p- bromobenzohydroxamic acid system 108 Table (49) Continuous variation method for Cr (Vl)-P-methy -N- phenyl-N-p- bromobenzohydroxamic acid system 109 Table (50) Continuous variation method for Cr (Vl)-P-methyl -N- phenyl-N-o-bromobenzohydroxamic acid system 110 Table (51) Continuous variation method for Fe (III) -N-phenyl-N-o- bromobenzohydroxamic acid system 111 Table (52) Continuous variation method for Fe (III) -N-phenyl-N-p- bromobenzohydroxamic acid system 112 Table (53) Continuous variation method for Fe (III) -P-methy -N- phenyl-N-p- bromobenzohydroxamic acid system 113 Table (54) Continous variation method for Fe (III) -P-methyl -N- phenyl-N-o-bromobenzohydroxamic acid system 114 Table (55) Continuous variation method for V (V) -N-phenyl-N-o- bromobenzohydroxamic acid system 115 Table (56) Continuous variation method for V (V) -N-phenyl-N-p- bromobenzohydroxamic acid system 116 Table (57) Continuous variation method for V (V) -P-methy -N- phenyl-N-p- bromobenzohydroxamic acid system 117 Table (58) Continuous variation method for V (V) -P-methyl -N- phenyl-N-o-bromobenzohydroxamic acid system 118 Table (59) Continuous variation method for Co (II) -N-phenyl-N-o- bromobenzohydroxamic acid system -„... 119 Table (60) Continuous variation method for Co (II) -N-phenyl-N-p- bromobenzohydroxamic acid system 120 Table (61) Continuous variation method for Co (II) -P-methy -N- phenyl-N-p- bromobenzohydroxamic acid system 121 Table (62) Continuous variation method for Co (II) -P-methyl -N- phenyl-N-o-bromobenzohydroxamic acid system 122 Table (63) Continuous variation method for Cu (II) -N-phenyl-N-o- bromobenzohydroxamic acid system 123
XIV Table (64) Continuous variation method for Cu (II) -N-phenyl-N-p- bromobenzohydroxamic acid system 124 Tublc (65) Continuous variation method for Cu (II) -P-methy -N- phenyl-N-p- bromobenzohydroxamic acid system 125 Table (66) Continuous variation method for Cu (II) -P-methyl -N- phenyl-N-o-bromobenzohydroxamic acid system 126
XV List of Figures and Appendices :
Fig (I) Calibration curve of Cr (VI) for the extraction with the four hydroxamic acids 52 Fig (2) Extraction curves showing distribution of Cr (VI) as a function of the acid molarity 58 Fig (3) Extraction curves showing distribution of Cr (VI) as a function of the pH 59 Fig (4) Calibration curve of Mo (VI) for the extraction with the four hydroxamic acids 62 Fig (5) Extraction curves showing distribution of Mo (VI) as a function of thepH 67 Fig (6) Calibration curve of Fe (III) for the extraction with the four hydroxamic acids 70 Fig (7) Extraction curves showing distribution of Fe (III) as a function of the acid molarity 75 Fig (8) Extraction curves showing distribution of Fe (III) as a function of the pH 76 Fig (9) Calibration curve of V (V) for the extraction with the four hydroxamic acids 79 Fig (10) Extraction curves showing distribution of V (V) as a function of the acid molarity 84 Fig (11) Extraction curves showing distribution of V (V) as a function of the pH 85 Fig (12) Calibration curve of Co (II) for the extraction with the four hydroxamic acids •. 88 Fig (13) Extraction curves showing distribution of Co (II) as a function of thepH 93 Fig (14) Calibration curve of Cu (II) for the extraction with the four hydroxamic acids 96 Fig (15) Extraction curves showing distribution of Cu (II) as a function of the pH 101 Fig (16) Continuous variation plot of Cr (VI)- N-phenyl-N-o- bromobenzohydroxamic acid 127 Fig (17) Continuous variation plot of Cr (VI)- N-phenyl-N-p- bromobenzohydroxamic acid 127 Fig (18) Continuous variation plot of Cr (VI)-P-methyl N-phenyl-N-p- bromobenzohydroxamic acid 128 Fig (19) Continuous variation plot of Cr (Vl)-P-methyl N-phenyl-N-o- bromobenzohydroxamic acid 128 Fig (20) Continuous variation plot of Fe (III) - N-phenyl-N-o-bromobenzo- hydroxamic acid 129 Fig (21) Continuous variation plot of Fe (III) - N-phenyl-N-p-bromobenzo- hydroxamic acid 129
XVII Fig (22) Continuous variation plot of Fe (III) -P-methyl N-phenyl-N-p- bromobenzohydroxamic acid 130 Fig (23). Continuous variation plot of Fe (III) -P-methyl N-phenyl-N-o- bromobenzohydroxamic acid 130 Fig (24) Continuous variation plot of V (V) - N-phenyl-N-o- bromobenzohydroxamic acid 131 Fig (25) i Continuous variation plot of V (V) - N-phenyl-N-p-benzohydroxamic acid 131 Fig (26) Continuous variation plot of V (V) -P-methyl N-phenyl-N-p- bromobenzohydroxamic acid 132 Fig (27) Continuous variation plot of V (V)-P-methyl N-phenyl-N-o bromobenzohydroxamic acid 132 Fig (28) Continuous variation plot of Co (II) - N-phenyl-N-6- bromobenzohydroxamic acid 133 Fig (29) Continuous variation plot of Co (II) - N-phenyl-N-p- bromobenzohydro-hydroxamic acid 133 Fig (30) Continous variation plot of Co (II) -P-methyl N-phenyl-N-p- bromobenzohydroxamic acid 134 Fig (3 1) Continuous variation plot of Co (II) -P-methyl N-phenyl-N-o- bromobenzohydroxamic acid 134 Fig (32) Continuous variation plot of Cu (II) - N-phenyl-N-o- bromobenzohydroxamic acid 135 Fig (33) Continuous variation plot of Cu (II) - N-phenyl-N-p- bromobenzohydroxamic acid 135 Fig (34) Continuous variation plot of Cu (II) -P-methyl N-phenyl-N-p- bromobenzohydroxamic acid 136 Fig (35) Continuous variation plot of Cu (II) -P-methyl N-phenyl-N-o- bromobenzohydroxamic acid 136 App ( A) Infrared absorption of N-phenyl-N-p-bromobenzohydroxamic acid 146 App (B ) Infrared absorption of N-phenyl-N-o-bromobenzohydroxamic acid 147 App (C ) Infrared absorption of P-methyl N-phenyl-N-p- bromobenzohydroxamic acid 148 App (D ) Infrared absorption of P-methyl N-phenyl-N-o- bromobenzohydroxamic acid 149 App ( \i) Ultra-violet absorption of N-phenyl-N-p-bromobenzohydroxamic acid 150 App (F ) Ultra-violet absorption of N-phenyl-N-o-bromobenzohydroxamic acid 151 App(G ) Ultra-violet absorption of P-methyl N-phenyl-N-p- bromobenzohydroxamic acid 152 App (II ) Ultra-violet absorption of P-methyl N-phenyl-N-o- bromobenzohydroxamic acid 153
XVIII Abbreviations: cm centimeter g gram mg milligram Mg microgram ppm parts per million lit literature °C degree centigrade m.p. melting point U.V. ultra-violet. I.R infrared nm nanometer (10" meter) wave length M molar mol mole A.R. analytical reagent G.P.R. general purpose reagent B.D.H . British Drug House H.W. 1 loppkin and Williams o- ortho P- para m- met a
XIX
1. INTRODUCTION
1.1 Analytical Chemistry : Jt means the resolution of chemical compounds into its ultimate parts. It can be thought of as comprising two branches, qualitative analysis which deals with finding what constituents are in an analytical sample and quantitative analysis which deals with the determination of how much a given substance is in the sample." 1.2. Methods of Analysis : The various methods of determination an analyte can be classified as: 1.2.1. Chemical Methods: These are mainly applied to the classical methods of analysis such as gravimetric analysis and volumetric or titrimetric analysis . The use of chemical methods has decreased sharply with the advent of physicochemical methods . 1.2.2. Physicochemical Methods: These are instrumental methods of analysis.They are more sensitive and selective than classical chemical methods.4"5 Physicochemical methods can be grouped as follows : (i) Optical methods: Based on the optical properties of the substance analysed, such as , photometry , refractometry and polarimetry. (ii) electrochemical methods: These include potentiometry, voltametry and conductivity. (iii) Physical methods: In which various physical properties of the substances are utilized, such as, thermal analysis, x-ray and mass spectrometric analysis. Most instrumental methods are based instrument which register a signal due to physical property of the solution. Spectrophotometer measures the fraction of electromagnetic radiation from a light source which is absorbed by the sample. Like gravimetric analysis , however an instrumental technique may include a seperation step. The most important of these methods of separation are, chromatography , ion exchange and extraction . (i) Chromatography: Gas chromatography , involves a seperation based on the interaction of solute gases with liquid or solid stationary phases, followed by measurement ofthe separated gases by a detector'. Other types of chromatography include adsorption chromatography (T.L.C) and fluid partition chromatography (L.C) (ii) Ion Exchange Method: This is particularly well suited for the seperation of inorganic ions both cations and anions . It has also proved to be extremely useful for the seperation of amino acids. Moore and Stein ", have successfully seperated up to 50 amino acids and related compounds on a single Dowex-50 cation exchange column by a pH control. The most important applications of ion exchange methods are seen in analytical seperation and the deionization of water", (iii) Extraction: Extraction is a widely used technique for the seperation, isolation and purification of substances . 1.3. Solvent Extraction: Solvent extraction involves the distribution of a solute between two immiscible liquid phases. This technique is extremely useful for very rapid and clean separation of both organic and inorganic substances, this is one advantage over the precipitation method . 1.3.1 Theories of Solvent Extraction: 1.3.1.1. Distribution Law: It was first elaborated by Nernest l5 in 1891 it states that (A solute will distribute between two essentially immiscible solvents in such a manner that at equilibrium the ratio of the concentrations of the solute in the two phases at a particular temperature will be constant, provided the solute has the same molecular weight in each phase). A solute S will distribute itself between two practically immiscible phases, the ratio of the concentrations of the solute in the two phases will be constant .
(1)
Where KD is the distribution coefficient and the subscripts represent solvent 1 (an organic solvent ) and solvent 2 (an aqueous layer ). If the distribution coefficient is large, the solute will tend toward quantitative distribution in solvent 1. Many substances are partially ionized in the aqueous layer, this introduces a pH effect on the extraction. If we consider the extraction of benzoic acid from an aqueous solution.
Benzoic acid (HBZ ) is a weak acid in water with ionization constant Ka given by :
Ka = [1 f]a [BZ']a (2)
[HBZ], The distribution coefficient is given by:
[HBZ]e (3)
[HBZ]£
Where : e represents the ether solvent . a represents the aqueous solvent. However, part of benzoic acid in the aqueous layer will exist as BZ" .depending on the magnitude of Ka and the pH of the aqueous layer, hence, quantitative seperation may not be achieved. 1.3.1.2. The Distribution Ratio: Disteribution ratio is the ratio of the concentration of all the species of the solute in each phase which is the most important factor in the analytical
1X 'i separation . In the above example: iIsS given by : A
[HBZ] e D = (4)
[ HBZ] a + [ BZ-]a
a relationship can be derive between D and KD . The acidity constant Ka for the ionization of the acid in the aqueous phase is given by: T [H ]a [BZ-]
[ MBZ]a hence:
Ka [MBZ]a
[BZ"]a = (5)
a from equation (3)
[IIBZ1L.= KD [ HBZ]a (6) by substitution of equation (5) and (6) into equation (4) gives.
KD[HBZ]a (7)
+ [HBZ]a + Ka[HBZ)a/[H ]a
KD (8) D -
l+Ka/[If]a
+ When [H ]a » Ka, D is nearly equal to KD.
If [H']a « Ka then D reduces to :
KD [ H'L D = Equation 8 like equation 1 predicts that the extraction efficiency will be independent of the original concentration of the solute."This is one of the attractive features of solvent extraction. 1.3.1.3. The percent Extraction: (Recovery) : The fraction of solute extracted is equal to the amount of the solute in the organic layer divided by the total amount of the solute . Thus the percent of extraction is given by:
[S]0V0 xlOO% (9) %E =
[S]o Vo + [S]a Va
dividing by [S]a Vo the percent extracted can be expressed in term of distribution ratio:
100 D (10) %E =
D + Va/V0 in the special case when the volumes of the two phases are equal then equation 10 tends to
100D (11) %E = D+ 1 Quantitative extraction is obtained when D is greater than 1000. The percent extracted changes only from 99.5 to 99.9 when D is doubled from 500 to 1000.
1.3.1.4 Successive Extraction : Equation 10 shows that the fraction extracted can be increased by decreasing the ratio of Va/Vo , as increasing the organic phase volume. However a more efficient way of increasing the amount extracted using the same volume of organic solvent is to perform successive extraction with smaller portions of
20 organic solvent . With a D of 10 and Va/V0 = 1 ,% E is about 91 % .But decreasing Va/ Voto 0.5 (doubling Vo), %E will increase to 95% . By performing two successive extractions with Va/ Vo = 1, overall % E is 99%. 1.3.2 Solvent Extraction of Metals:
One of the most important applications of solvent extraction is the seperation of metal cations""1. Metal ions do not tend to dissolve appreciably in the organic layer. For them to become soluble their charges must be neutralized . There are two principal ways of doing this" : 1.3.2.1 Ion Association Complexes : The metal ion associates with another ion of great size (organic - like ), as in iron (III) can be quantitatively extracted from hydrochloric acid medium into diethyl ether { ( C2 H5)2 O: H\ FeCl4 [ C2H5)2O]\ }. Similarly, the uranyl ion
UO2~' is extracted from aqueous nitrate solution into isobutanol by association 2r with two nitrate ions, (UO2 , 2NO"3) 1.3.2.2 Metal Chelates: This is the most widely used method of extracting metal ions and form a chelate molecule with an organic chelating agent which contains two or more complexing groups, many of these reagents form coloured chelates with metal ions and form the basis of spectrophotometric methods for determination of the metals" ' 1.3.2.3 Extraction Process: The ionizable proton in the chelating agent is displaced by the metal ion when the chelate is formed, and the charge on the organic compound neutralized the charge on the metal ion as in diphenylthiocarbazone (dithizone) which forms a chelate with lead ion. pb/2
l/2pb 2+ - C=S +H
- N = N
Green Red Extraction process consists of four equilibrium steps : Aqueous phase H" +R" 11
n+ (HR)a nR' + M ^(MRn)a 11
(HR)0 (MRn)0 Organic Phase. First step, the chelating HR distributes between the two phases:
(HR)0 ^±(HR)a distribution coefficient of the reagent = KDHR = [HR]0 (12)
[HR]a Second, the reagent in the aqueous phase ionizes HR ^H+ + R"
+ The ionization constant = Ka = [ H ] [R~] (13)
[HR]
Third , the metal ion chelates combinde with the anion to form uncharged molecule (chelate): M"+ + nR" ^
The formation constant = Kf= [ MRn] (14)
Finaly , the chelate distributes between the two phases:
(MRn)aq ^
The distribution coefficient of the chelate = KDMRn = [MRn] 0 (15)
[MR ] n a
9 Assuming that the chelate portion of the metal distributes largely into the organic phase and that the chelate is essentially undissociated in the non polar organic solvent, the distribution ratio D is given by:
D =
+ [Mn ]a
By substituting the appropriate equilibrium concentrations from equation (12) through (15) into equation (16) the following equation can be derived.
n n n KDMRn KrK a [HRJ Or K. [HR] Or (17) D= =
n + n K DHR [U ]\ [H+] aq From equation 17 , the distribution ratio is independent of the concentration of the metal ion, and affected only by changing the reagent concentration or by
21 changing the pH . TJv* more stable the chelate (the large the kf) the greater the extraction efficiency ,e "But chelate stability decreases as the reagent acidity increases. From equation 17, if reagent concentration remains virtually constant then:
n D =K*+[H+] a ([8)
n Where K = K [HR] or and the percentage of solute extracted (E) is given by:
10 logE.log(lOO-E) = logD
= logK* + npH (19) Where n is the charge of the metal. The distribution of the metal in a given system is a function of the pH alone.
If pH,/2 is defined as the pH value at 50% extraction (E% = 50), from equation (19).
pH1/2= -1/nlogK* (20)
if the difference in pH,,2 of two metals values are far apart then excellent seperation can be achieved. The pH|,2 values may be altered by the use of masking agent/Thus in seperation of mercury and copper by extraction with dithizone in carbon- tetrachloride at pH 2, the addition of EDTA forms a water- soluble complex which completely masks the copper but does not affect the mercury extraction . 1.3.2.4. The Seperation Efficiency of Metal Chelates: The seperation factor, p, is equal to the ratio of the distribution ratios of the two metal chelates formed with a given reagent* mis can be predicted from equation 17, since only Kf and KDMRn will be a function of the metal then:
D, Kf(-l)KDRMn(l) (21) ft = =
D2 Kf(2)KDRMn(2) The specifity of extraction may affected by the solublities of the chelates and steric hinderance, as 8-hydroxyquinoline (oxine) forms a chelate with many metals including aluminum" . But 2-methyl-8-hydroxyquinoline will not form a complex because the added methyl group does not allow the molecule to group around this ion. Addition of masking agents will increase the selectivity of extraction. EDTA and cyanide ion are commonly used as masking agents . Thus,
+ although Cu~* forms a more stable complex with oxine than VO2 Adoes, the vanadium may be extracted in the presence of copper by the addition of EDTA,
2 2 which forms an even more stable complex with the copper (Cu-EDTA ") . 1.4 Analytical Seperations : One of the most important applications of solvent extraction is the spectrophotometric determination of metals in the visible region. Many organic reagents form coloured chelates with metals, but most of the chelates are insoluble in water and soluble in organic solvents and can easily be extracted.. Solvent extraction is widely employed in drug analysis " . 1.4.1. Multiple Batch Extraction: Quantitative extraction is efficiently carried out by performing multiple extraction with smaller portions of the same volume of the two phases , it is useful for calculations with multiple extractions to compute the fraction- of analyte remaining unextracted after a given number of extractions". Division of equation
(10) by 100 gives the fraction extracted [ D / (D+Va / Vo)]? substraction of this from 1 gives the fraction F remaining unextracted.
F=l-D/[D+Va/Vol (22)
12 which can be rearranged to
F= Va/DV0+Va (23)
After the first extraction, fraction of solute in aqueous solvent
Wal (24)
W;
Then : WaI Cal Va = (25)
w, calva+cOIvOI
Va+ Col Vol (26)
Va .(27)
Va + DV0
13 V a
Wal = Wj (28)
Va + DV0
The second extraction is the same as the first, except that Wal is present instead of Wi. Thus:
Wa2 = Wal Va (29)
Va + DVr0
Wi, Va V
) (30) repeating the precedure through n extractions gives:
w = W- / V v nn
V, + DV0
1.5 Orgainc Reagents in Analytical Chemistry: Organic reagents have considerable sensitivity and selectivity towards metal ions that why they play important role in chemical analysis" . Many metal ions can be seperated alter reaction with an organic reagent, the metal ions are generally held in ring configuration and the precipitates formed are of high molecular weight, stable to drying, coloured and insoluble in water, but soluble in non-polar solvents The binding of an organic reagent by a metal form organometallic compound, and the groups bound to the centre ion are called ligands27"28. 1.6 Some Applications of Organic Reagents in Analytical Chemistry: 1.6.1. Gravimetric Analysis: There are a large number of organic compounds that are very useful in precipitating metal ions" . Organic precipitating reagents have the advantages of giving precipitates with ' very low solublity in water and a favourable gravimetric factor30. Dimethylglycoxime is the one of most selective organic reagent for Ni ~,pd ", pt*~ and BTJ ionsJ . Also 8-hydroxyquinoline (oxine) precipitates many metals , but useful for Al (III) and Mg (II).. Organic reagents are generally weak acids , so the number of elements precipitated and the selectivity can be regulated by the adjustment of the pH. 1.6.2 Complexing Reagents: Most of organic agents are chelating reagents that form slightly soluble, uncharged chelates with the metal ions . The complex formed is called a chelate ". The formation of these complexes serves as the basis of accurate and convenient titrations for metal ions, by the use of appropriate masking agents and pH control. Many metal ions form complexes in solution with a variety of substanes that have a pair of unshared electrons as on N,0 and S Ethylenediaminetetraacetic acid (EDTA) is a useful reagent for compleximetric titrations for the determination of metal ions such as zinc , magnesium, calcium, lead and stannous. EDTA is represented by the symbol H4Y.
It is a tetraportic acid and the hydrogens in H4Y refer to the four jonizable hydrogens on the four carboxyl groups, and the unprotonated Y " forms complexes with so many metal ions'. 1.6.3 Colourimetric Analysis: Many organic reagents form coloured chelates, with metals . Examples of reagents used in colourimetric analysis are dimethylglucoxime, dithiazone, 8-hydroxyquinaline and N-phenylbenzohydroxamic acid " . When the ligand bound to the metal at one point this is a monodentate ligand , and is said to be bidentate when the ligand has two donor atoms as in the hydroxamic acids functional group and the complex formation takes place with the replacement of the hydroxylamine hydrogen by the metal ion and ring closure through the carbon oxygen "J . 1.7 llydroxamic Acids: Hydroxamic acids are important chelating agents, towards a very O OH great number of metal ions . They have bidentate functional group (-C - N -), that fulfils the basic requirements of complex formation with metal ions and , therefore , form an important family of chelating reagents. Hydroxamic acids have many applications in_analytical chemistry, ! \ specially in spectropholometry, gravimetry and titrimetry,They also have useful application in medicine . and biology . Several of them have been used as drugs , and for the solvent extraction in determination of metals. 1.7.1 Structure of Hydroxamic Acids: Hydroxamicjpds may be regarded as derivatives of both hydroxylamine and carboxylic acids.lhey exist in the two tautomeric forms, keto(l) and enol (11) form45'
16 H-N-OH tautomeric N - OH
\ II I II \ R-C = O R- C-OH
(1) (11) Keto form becomes the more stable form due to hydrogen bonding, it contains one easily replaceable proton (monobasic acid), while enol form dissociates two protons (dibasic acid). The keto form predominates in acidic solution, while the enol is the dominant form in alkaline medium4 . Hydroxamic acids have the general formula:
O OH R-C-N-R Where R and R could be hydrogen, alkyl or aryl groups. They have been classified as primary (III), secondary (IV) or cyclic (V).
H-N-OH R-N-OH N-OI-
I
R-OO
(111) (V) (IV)
Unless the structure is hindered, most hydroxamic acids will be hydrogen bonded and exist in the keto form, " bound to a transition metal via the oxygen atoms49:
17 R-N-OH + M1 R-N-CT n I R-C = O R - C = O +nH+
Mizukami• 5U and Nagata have replaced the oxygen atom by sulphur atom to get thiohydroxamic acid (VI) and (VI1).
H-N-OH tautomeric N-OH l ^ II \ R-C - S R-C-SH
(VI) (VII)
1.7.2 Preparation of Hydroxamic Acids: Several methods for preparation of hydroxamic acids have been described by Yale5 . They were first prepared from carboxylic acid via their methyl or ethyl esters or anhydride by reaction with hydroxylamine in alcohol or alkali 3"° . Other methods, although satisfactory in certain instances, have limited applications: (a) The reaction between an ester and hydroxylamine.
RCOOH CH^OH RCOOCH3 NH.0H.HC1 RCONHOH.
> 2, NaOH (b) Acid chloride method in which hydroxylamine is acylated with an acid chloride, acid anhydride or ester 54-55
18 R'-N-OH + R-C=O • R-N-OH I i I +HX II X R-C - O Where X =C1,-OCOR, - OR. (c) Reaction between hydroxylamine , water-soluble aldehyde (e.g formaldehyde and acetaldehyde) and hydrogen peroxide .
-> M-N-OM I RMC - 011
I-N-OH N-OM
+2H2O RH-C-01I RC-OII (d) The reaction between carboxylic acids, carbodiimides and hydroxylamine57.
RCOO11 t-RN = C= NR + NM2OH >RCONHOH+R*NH-CO-NHR (e) Most carboxylic acid imides, react in basic media with hydroxylamine to form hydroxamic acids. Succinimides, formhydroxamic acid which quickly cyclizes in the basic media to form N-hydroxysuccinimide .
o 0 Ji . C - N11CJ11 Nil Nil,OH
V_P- - MINIH l- p ^ II II 0 0 Succinimide
0 0 n — ii - L - N -on c last X N - Oil C-Nlh c d N-hydroxysLiccinimide
19 (f) Reaction between isocyanate and hydroxylamine 5..
R-N=C=O+NH,OH >R-NHC.OH N II ^ N.OH R-NH-C=O I H-N- OH
(g) The reaction between carboxylic acid and hydroxylamine in the presence of Ni (11) as a catalyst60.
R COOH + NH.OH Ni (11) H-N-OH
". > I +H9O R-C-0 (h) Thiohydroxamic acids, are sulphur analogous of hydroxamic acids, they are prepared by the reaction of dithocarboxylic acids, dithiocarobylic esters and acid chloride . They can be also prepared by the reaction of hydroxylamine with isothiocyanate l. 1.7.3. Properties of Hydroxamic^cids: Generally , hydroxamic acids are white solids 62, except iodosubstituted and cinnamo- which are light pink and light yellow respectively . They are inoluble in water, sparingly soluble in carbon tetrachloride and cold benzene, but readily soluble in hot benzene ,diethyl esther, dioxane, chloroform and ethanol. They have lower melting points. 1.7.4 Defection of Hydroxamic Acids: The most characteristic reaction of hydroxamic acids is the red violet colouration develops with ferric ion in acid media . Agrawal 65 reported a method which based on two assumptions, that all hydroxamic acids are soluble in chloroform and that the violet complex with all
20 the hydroxamic acids formed with vanadium (V) can be extracted into chloroform, this method failed to detect certain hydroxamic acids in which the complexes are insoluble in chloroform . 1.7 5 Acidity of Hydroxamic Acids: The acidity of hydroxamic acids arises due to the presence of hydroxyl group which causes intramolecular hydrogen bonding as shown by infrared studies .
O Hv R —C O \ N / H Cyclic hydroxamic acids in the solid state are capable of intramolecular and intermolecular hydrogen bonding .
- N - ON / C I H ^ II /C - C = O H- O O N \)
H - 0 H Intramolecular hydrogen bonding Intermolecular hydrogen bonding.
CO Exner and Kack reported that the proton bound to the nitrogen atom in the hydroxamic acid is and acidic proton, and ionization gives rise to the anions. O O _ O~ R-d-NHOH —> R-£-N -OH <-> R-C^N-OH + H+ It was reported that two anions are formed in essentially equal concentrations as in equilibrium below :
O O _ R-£-NHO~ N R-^-N-OH
21 70 Agrawal and Tandon have measured the ionization constants (pKa) often N- arylhydroxamic acids in aqueous media at different temperature.
The Pka value decreases when the hydrogen attached to the nitrogen is replaced by a phenyl group (-1 effect),so the lone pair of electrons of the nitrogen resonating with the six n -electrons of benzene ring attached to it, this make , the nitrogen election diffident centre and the proton will liberate easily. pKa values of hydroxamic acids are influenced by introduction of groups having either - ve or
+ve I effect and substituents in N-phenyl ring, that why the pKa value of phenylacetohydroxamic acid (VI11) is 10.071, and decrease when the hydrogen is replaced by a phenyl group , e.g N -2-diphenylacetohydroxamic acid (IX) is 9.80 .
11-N-OH C6H5-N-OH C6H5-CHrC=O C6H5-CHrOO
(VI11) (IX)
pKa values of hydroxamic acids derived from amino acids (R-CH (NH2) CONHOH) determined by pH-metric titration , the values are in line with the basicity of the corresponding amino acids ". The most simple aminohydroxamic acid can liberate two protons, one from amino group and other from hydroxamic acid group and these acids have complicated acid -base properties, some conclued that the NH+ group is more acidic ,73 while others have taken the opposite view.53
According to measurement of pKa values thiohydroxamic acids are found to be stronger acids than the corresponding oxygen compound and hyroxamic acids are stronger acids than phenol35. The infrared spectra of hydroxamic acids show the most characteristic bands associated with the hydroxamic acid functional groups those due to the (O- H),(O0)- (N-O) and (C-N) stretching vibrations, these frequencies are generally aiTOiind 3200, 1600, 910 , and 1385 cm"1 respectively74. Coutts and Elizabeth75 have observed that the position and intensity of the carbonyl and the hydroxyl infrared absorption bands vary considerably from one hydroxamic acid to another . An intramolecularly hydrogen-bonded carbonyl group absorbs infrared radiation at a lower frequency than the corresponding intermolecularly hydrogen-bonded carbonyl group . In addition, when hydrogen- bonding is intramolecular, the O-H stretching band is usually broad, where as a sharp hydroxyl absorption is obtained when hydrogen bonding is intermolecular.
Earlier data in hydroxamic acids has indicated that the O-H stretching of the free unassociated hydroxyl group of-N-O-H is very strong band in the region 3 195-3170cm"1, the O-H stretching vibration of the hydroxyl group which is engaged in hydrogen bonding with the carbonyl group is found as a weak to strong on the low frequency side of the main O-H band in the region 2910 - 2850 cm"1' Similarly the O-H deformation vibration is found to be in the region 1100-1000 cm" as strong sharp band. Further all three bands disappear upon coordinateion with a metal ion, this interpreted as evidence that the ligands co-ordinate through hydroxyl oxygen, and that on co-ordination of the acid the hydroxyl proton is replaced by the metal ion . In the case of salicyiohydroxamic acid SHA the spectra is some what complicated due to the presence of additional phenolic O-H group . So the frequency assignments are not straight forward. C = O [ v (C-O)] vibration in SHA in the region 1700-1400cm"' this low frequency indicates both conjugation and hydrogen bonding .
23 Babat and Black have shown that the carbonyl absorption frequencies of cyclic hydroxamic acid (X) are lower than those of the corresponding lactams (XI) probably because of more effective intramolecular hydrogen bonding in the former one.
N - OH N-H
(X) (XI)
Ultra-violet spectra for aryl hydroxamic acids and their N-and O- substituted derivatives show a large wavelength absorption (220-260 nm)
O 1 associated with the aryl ring Other spectral analysis are used to elucidate the structure of hydroxamic acids, for example x-ray diffraction ", nuclear magnetic resonance83, electron spin resonance 84 and mass spectra. 1.8 Some Applications of Hydroxamic Acids: 1.8.1. Gravimetric Determination: Hydroxamic acids having a phenyl group attached to the side chain have been found to be useful reagents for gravimetric estimation of metals, like copper(ll), nickel (11), cadmium (11), cobalt (11), mangenese (11), titanium (IV), zirconium (IV), iron (111), vanadium (V), uranium (VI), niobium (V) and tantalum (V) this due to their insolubility in aqueous media69. o c N-phenylbenzohydroxamic acid used by Sinha to separate cobalt and nickel from copper by adjusting the pH. Moshier and Schwarberg used the same reagent to separate tantalum (V) from other metal ions . Also tin in brass sample was precipitated from acidic medium by N-phenylbenzohydroxamic
24 ft "7 acid . Thorium and cerium were precipitated gravimetrically by the same reagent o o at pH 5 and pi I 7 respectively . Agrawal and Roshania used N-p-chlorocinnamohydroxamic acid to separate and determine beryllium , magnesium, calcium , and barium by using masking agents and adjusting pH. Afew hydroxamic acids have been found to serve as suitable indicators in the compleximetric titration of ferric ion with EDTA69. 1.8.2 Hydroxamic Acid Resins: Hydroxamic acids resins have attracted attention as analytical reagents, owing to their good complexing behavior with a broad range of metal ions . Initial attemps to prepare a poly (hydroxamic acid) chelating exchange resin involved the conversion of conventional weak cation exchangers to acid chlorides followed by reaction with hydroxylamine91"92. Kern and Schultz93 converted a linear poly (methylmethacrylate) to a poly (hydroxamic acid), (PHA), with 80 % efficiency and found that Fe (111), Cu (11), Ag (1), Zn (U),Hg (11), Al (111) and Pb (11) gave precipitates with the polymeric ligand. Schonteden converted poly (acrylonitrile) to PHA by reaction with hydroxylamine in dimethylformamide . Vernon and Eccles 3 prepared a cross-linked PHA ion exchanger by polymerising an acrylonitrile-divinylbenzene mixture , subjecting the resulting granular polymer to hydrolysis in 50 % sulphuric acid and reacting the polyamide produced with hydroxylamine solution . Several resins applications were studied, particularly the use of PHA in extracting trace metals from sea-water. Veron and Kyffin used this resin to separate Fe (111), Cu (11) and U (VI). An advantage of the PHA resin is that it is 97 prepared from low cost materials and the kinetic properties not varying .
2.1) 1.8.3 Spectrophotometric Determinations: Hydroxamic acids are among the most selective and sensitive reagents for the spectrophotometric determination of several metal ions.Then intense colouration given by many metal ions with hydroxamic acids makes the latter often useful as colourimetric reagents69. The most characteristic reaction of the hydroxamic acid is red-violet colouration develops with ferric ion in acid medium 98 below PM2 and the orange complexes which develop gradually above pH 3 Vanadium reacts with certain hydroxamic acids specially with those having another functional group attached to the side chain yielding complexes with different colours at different pH. Wise and Brandt" extracted 97% of V (V) by benzohydroxamic acid in 1-hexanol at pH2. Among twenty seven N- arylhydroxamic acids studied, N-phenylcinnamohydroxamic acid was found to be the most sensitive reagent for determination of V (V) spectrophotometrically N-m-chlorophenylcinnamohydroxamic acid was found to be another sensitive reagent for determination of V(V), which extracted from 4M to 7M hydrochloric acid by 0.1% (w/v) chloroform solution of the reagent 10 . Gupta and Tandon l02 developed a method to determine V (V) by the use of highly selective and specific N-m-tolyl-p-methoxy benzohydroxamic acid. N-p-chlorophenyl-2- naphthohydroxamic acid was used to determine V (V) in trace quantities in sample of various origin including determination in blood103. The colour of vanadium complexes of some hydroxamic acids develops slowly like N-phenylphenoxyaceto and N-p-chlorophenoxyacetohydroxamic acids, that means acids, are unsuitable as extractive reagents for V (V). Some nitrosLibstituted hydroxamic acids which are coloured, are unsuitable for colourimelric determination of V (V).
26 Vanadium hydroxamic acid complexes were found to be very stable and back extracting with nitric acid and oxalic acid failed to strip the vanadium. Sulphuric acid can strip after a long time of shaking but will destroy the tigand. Chloroform is the most suitable solvent for the extraction of V (V) because the colour of chloroform extract is found to be stable up to five days and is not affected by temperature, while the extraction is very poor and the violet colour disappeasr within 5-10 minutes when amyl alcohol and n-butylalcohol are used. The interference due to various ions in the determination of V(V) was studied with N-p-chlorophenyl 2-naphthohydroxamic acid l04 32.5 fig cm"1 of vanadium in 15 cm of aqueous solution may be determined in presence of Ba , Ca" Cc\~ , Cu~ , Zn" , FeJ^ and Ni"7 each in the amount' of 30 mg. The interference due to Ti (V), Mo (VI) and Zn (IV) in the same quantity (30 mg) is eliminated by adding sodium fluoride and ammonium oxalate before extraction. Another interference can be due strong reducing agent that convert the V(V) to
Uranium (VI) and benzohydroxamic acid was developed for spectropholometric determination by Meloan, the colour of complex is dependent, on pll . Versatohydroxamic acid used by Abdalla for extraction of Mo (VI) V(V) Cu (11), Ni (11) Mn (II) , Zn (11) and U (VI) at different concentration from synthetic sea-water. Karrarl06used the same reagent in xylene to determine V(V). Agrawal used N-phenylcinnamohydroxamic acid to determine Cd (11) as yellow complex in chloroform at pH 9.5. Fe (111), Cu (II) and Ni (11) have been extracted with benzohydroxamic acid which gives the most effective iron copper separation from nickel . There are many factors affecting the extractability of-the hydroxamic acids including, the pll of the medium " , the alkyl substituted and the donor atom
27 1.8.3.1 Stripping : It is the removal of the extracted solute from the organic phase . If the organic solvent is very volatile (diethyl ether) the simplest way is to add small volume of water and evaporate the solvent continuously on a water-bath; when the extraction solvent is non-volatile stripping is performed by shaking gently with an aqueous solution of acid or base .
28 Table (1) : Some hydroxamic acids used for the extraction of some metals.
-hydroxamic acid structure M pll %E Ref. Hydroxamic acids mixture q from cotton-seed oil and C15H3,-(!:-NHOH V(V) 2 93 114 semsame oil. + o C17II13-C-NHOH Fe (III) 5.5 100 + 0 C,7H3l-t-NHOH Ni (II) 6 25 Cu (II) 6.5 89.7 Zn(II) 7 72
Hydroxamic acids from (HNO3 - cotton-seed oil Mo(VI) 0.5M 99 Ti (IV) 4M 65 115 U(VI) O.IM 35 Zr (VI) O.IM 100 on 9 V 1 /"* N-phenyl-o-chlorobenzo- U(VI) 7 85 droxamic acid C°JC°JCI V(V) 1 100 116
OH 9, N —"9 N-phenyl-p-chlorobenzo- U(VI) 7 95 116 hydroxamic acid V(V) 1 100 Cl N-p-chlorophenylbenzo- OH 9 U(VI) 6 73.8. hydroxamic acid X. X V(V) 1 100 116 0 0 Cl
OH O N C N-phenyl-o-methoxyben- (o\ r^rocn3 U(VI) 7 100 117 zohydroxamic acid V(V) 1 96 on o
N-phenyl-p-methoxbenzoh- U(VI) 7 100 117 ydroxamic acid OCH, V(V) 1 97
29 Table (1): Continued".
-hytlroxnmic acki structure M %E Ref. P-chloro-N-phenyl-p OH o U (VI) 100 117 methoxybenzohydroxamic N_ C V(V) 100 acid. o o o en.
OH o p-chloro-N-phenyl-p-chloro- V(V) 3 118 benzohydroxamic acid 5 o o Fe (III) Co (II) 7 Cl Cl Cu(II) 5
OH O 21.7 119 N-phenyl-N-benzohydroxa- N C Ti (IV) 5 mic acid Cr(VI) MH9S 77.5 O4
Fe (III) 5 87.5 Mo(VI) 1 94.25
N-p-chlorophenyl-N-benzo- Ti (IV) 5 10 119 hydroxamic acid Cr (VI) 3M 57 Fe (III) 5 70 Mo(VI) 2 90
N-p-chlorophenyl-N-p- Ti (IV) 5 10 119 chlorobenzohydroxamic acid Cr(VI) 3M 57.5 Fe (III) 5 47.5 Mo (VI) 2 83
N-phenylbenzohhydroxa Cr (VI) 1 99.6 120 mic acid. OH o c N-p-tolylphenyi-N- o Mo (VI) 95 121 benzohydroxamic acid -v U(VI) 100
30 Table (1): Continued:
-hydroxuniie acid structure M PH %E Rcf. on 9 N-p-tolylphenyl-N-p-nitro- N__ c Mo(VI) 1 94 benzohydroxamic acid U(VI) 8 100 121 CH, NO, TI (IV) 5 11 Cr (VI) 3M 55
Salicylohydroxamic acid Cu (II) 3.8 122 resin Co (II) 3.8 - o Fe (III) 6.4 C-NHOH Ni (II) 6.4 - (VY on Salicylohydroxamic acid Fe (III) 6 99 61 Cu (II) 7 100 V(V) 4 98 Mo(VI) 1 95 . Ti (IV) 5MHC1 71 U(VI) 5 92 Ni (II) 6 7 Co (II) - 0
0 Phenylsalicylohydroxamic C-NOHph Fe (III) 2 100 61 acid Cu(II) 6 100 V(V) 1 98 Mo(VI) 2 92 Ti (IV) 6MHC1 89 U(VI) 5 57 Ni (II) 7 9 Co (II 7 3.5 61 O-methoxybenzohydroxamic Fe (III) 5 98 acid — Cu (II) 6 97 V(V) 3 100 Mo(VI) 2 98 Ti (IV) 4MHC1 88 U(VI) 5 77
31 Table (1) : Continued:
-hydi oxiunic acid it rue (ii re M pll %E Rcf. Stearohydroxamic acid H-N- OH Ti (IV) 4.5 70 123
C17H35 C=O Fe (III) 6 80 Ni (II) 7 3.6 Cu (II) 6 75 Zn(II) 7 2.4 U(VI) 7 94 V(V) 3 19.7 Mo (VI) 1 41.5
N-phenylstearohydroxamic C6H5- N - 011 Ti (IV) 6 89 123
acid C17H35C=O Fe (III) 5,6&7 96 Ni (II) 6 4.2 Cu (II) 6 88 Zn (II) 7 8.2 U(VI) 6 93 V(V) 3&4 24 Mo (VI) 1 42
Oleohydroxamic acid H-N- OH Ti (IV) 5-7 93.7 123
CI7H33C=O Fe (III) 4 90 Wi (II) 5-7 3.5 Cu (II) 6 78 Zn (II) 7 7 U(VI) 6 90 V(V) 3 20 Mo (VI) 1 96.2
N-phenylo!eohydroxamic • C6H5-N-OH Ti (IV) 5 .78 123 acid C17H33C = O Fe (III) 5 97, Wi (II) 7 4.5 Cu (II) 6 94 Zn (II) 7 18 U(VI) 6 84.5 V(V) 3-4 23 Table (I) : . Continued:
-hyriroxiunic acid structure M %E ftef. N-p-chlorophenyl-o- Cr (VI) 3M 100 124 methoxybenzohydroxamic on 9 Mo (VI) 1 92 acid N.. r Ti (IV) 2 26 0CH ri rV ; Fe (III) 3 .97 V(V) 3 100 a N-p-chloropbenyl Cr(VI) 1.2&3M 100 124 salicylohydroxamic acid 9 Mo (VI) 1 96 K" C N — L Ti (IV) 2 28 Fe (III) 5,6 100 V(V) 1.2&3M 100 Cl
N-p-Chlorophenyl-p-nitro on 9 Cr (VI) 3M 94 124 benzohydroxamic acid Mo (VI) 1 93 Ti (IV) 5 40 Fe (III) 3-6 100 ;-, NO, C1 - V(V) 3 100
N-p-chlorophenyl-o- OH 9 Cr (VI) 3M 100 124 chlorobenz hydroxamic acid N —c Mo (VI) 1 92 Ti (IV) 5 24 Fe (III) 3-5 100 Cl V(V) 2-3 100
N-p-chloro-m-chlorobenzo- on o Cr(VI) 3M 79 124 hydroxamic acid N c Mo (VI) 1M '• 96 6 38 fo" 1 fo"! Ti (IV) Fe(IH) 6 100 Cl V(V) 1-3M 100 pHI-3 Table (1) : Continued:
Monomethylphlhalate -2- Fe (III) 6 45.7 125 potassium hydroxamate OK V(V) 2 51.2 (MMPPH) ft ' Mo (VI) 2 60 C - N % Cd (II) 6 28.7 ^-~^-- C-OCH3 Cu(II) 5 26.7 (S U(VI) 6 -38.8
N-phenyldihydroxamate Fe (III) 6 48 125 f\ r>L. \J ill potassium salt. U 1 V(V) 2 60 C N r-^^V " Mo (VI) 1 50
0 Cd (II) 5 35,5 Cu (II) 6 48.3 U(VI) 6 54.1
Amino phthalic anhydride Fe (III) 6 89 125 f~\ 1 ] ft ' V(V) 2 75 Mo (VI) 1 60 c Cd (II) 5 36.1 0 Cu(ll) 6 47 U(VI) 6 97
The previous studies show that bromosubstituted hydroxamic acids are excellent complex formers and have been used for gravimetric and spectrophotometric determination of a number of metal ions. Thus the present investigation deals with the preparation of four hydroxamic acids and their applications for the extraction of Mo (VI), Cr (VI), V (V), Fe (III), Co (II) and Cu (II).
34
2- EXPERIMENTAL AND RESULTS Instruments used: (i) Jenway, pH meter, Model 3030. (ii) Mettler, Melting-point determination apparatus, (iii) LJ.V/Vis spectrophotometer, perkin Elmer 550 S. (iv) l.R. Spectrophotometer, Perkin Elmer 1330. 2.1. Preparation of Hydroxamic Acids: 2.1.1. Preparation of N-phenylbenzohydroxamic Acid: Reagents: ( i ) Ammonium chloride, A.R., (H.W). ( ii ) Ammonia solution, (B.D.H). (iii ) Sodium chloride, (A.R.), (B.D.H.) (iv ) Sodium hydrogen carbonate. A.R. (HW). ( v ) Zinc dust, G.P.R, (H.W). ( vi ) 1 lydrochloric acid, A.R., (B.D.I 1.). (vii ) Sulphuric acid, A.R.(H.W) (viii) Benzoyl chloride, G.P.R.(H.W.). (ix ) Benzene, A.R., (M.W.) (x) Dieihyl ether, A.R.(H.W. (xi ) Nitrobenzene , A.R.,(B.D.H). 2.1.1.1. Preparation of P-phenylhydroxylamine: 49.2 g (0.4 mol) of nitrobenzene, 25.0 g (0.47 mol) of ammonium chloride and 800cm3 distilled water were placed in a two litre beaker equipped with a thermometer and mechanical stirrer. The mixture was heated to about 55°C while stirring vigorously. Then 59.5g (0.9 mol) of zinc dust were added during 15 minutes keeping the reaction temperature between 60-65°C until all zinc dust has been added . Stirring was continued for further 15 minutes until the reaction was completed, this was indicated by the decrease in the reaction temperature. The warm reaction mixture was filtered under suction to remove the zinc oxide and washed with hot water. The filtrate was placed in a conical flask and saturated with sodium chloride, stirred vigorously and cooled in an ice-bath for at least one hour' .
Needle -shaped , pale yellow crystals were filtered and recrystallized from benzene yield 30.0 g (69%). m.p.81°C ( lit 81°C)34. NO, H-N-OH
ll J u o I ' -^ ' ^ " ""^ I o I + 2ZnO NH4CL
2.1.1.2 The Coupling Reaction Between P-Phenylhdroxylamine and.BenzoyI chloride: 27.5 g (0.15 mol) of freshly prepared P-phenylhydroxylamine were dissolved in 200 cm of diethyl ether in 500 cm beaker and stirred mechanically in an ice bath at 0°C with a suspension of 38.0 g (0.45 mol) of sodium hydrogen carbonate in 50.0 cm3 of distilled water126. 35.2 g (0.25 mol) of benzoyl chloride were dissolved in 100.0 cnV of diethyl ether and placed in a dropping funnel and
36 added dropwise to the cooled reaction mixture during a course of an hour. After the addition of benzoyl chloride had finished, the stirring was continued for further 30 minutes. The granular white precipitate was filtered under suction, washed with water, dried and weighed 39.8g (74%). This product is mainly N- phenyl benzohydioxamic acid contaminated with the disubstituted derivative. The acid was extracted with concentrated ammonia ,diluted with water, cooled and acidified with cold 20% v/v sulphuric acid until just acidic. The hydroxamic acid produced was filtered and recrystallized from distilled water. The yield 35.0 g (62%).
II-N-OH COC1
OT f:ther I u J L u J + Hcl L
NaHCO3
2.1.2. Preparation of N-Phenyl-N-p-bromobenzoliydroxamic Acid: Reagents: ( i ) P-bromobenzoic acid,A.R., (B.D.H) (ii ) Thionyl chloride (redistilled), A.R., (H.W.) (iii ) Sodium hydrogen carbonate, A.R., (H.W). (iv ) Diethyl ether, A.R., (H.W.) (v ) Petroleum ether A.R., 40-60°C, (B.D.H.) (vl ) Benzene,A.R.,(H.W.)
37 2.1.2.1 Preparation of p-bromobeirzoyl chloride " : 20.0 g (0.1 mol) P-bromobenzoic acid were refluxed*with 25.0 g
(0.21mol) redistilled thionyl chloride until the reaction was complete, the excess thionyl chloride was then distilled off as far as possible on the steam bath; then the acid chloride cooled, collected, washed with water and recrystallized, yield 18.0g, (82.5%). m. p (40-41°C) ( lit 37 - 40 °C) .
COON COC1 I i o I -i- SOCI-, A lo I + SO, + HCI
Br Br
2.1.2.2. Preparation of p-phenylhydroxylamine: fi-phenyIhydroxylamine was prepared as in 2.1.1.1.
2.1.2.3. The Coupling Reaction Between P-phenylhdroxylamine and P- bromobenzoyl chloride " . 10.9 g (0.1 mol) of freshly prepared pVphenylhydroxylamine were dissolved in 150.0 cm diethyl ether in 500 cm beaker and stirred vigorously using a mechanical stirrer in an ice bath at 0°C with a suspension of 16.8 g (0.2 mol ) of sodium hydrogen carbonate in 50.0 cm of water. 21.9 g (0.1 mol) of p~ bromobenzoyl chloride were dissolved in 100.0 cm3 diethyl ether and placed in a separator)' funnel and added diopwise to the cooled reaction mixture within one hour. After the addition had finished , the ice-bath was removed and the stirring continued at room temperature , at first the product appeared as an oily layer, then
38 solidified after the evaporation of the ethereal layer. The product was filtered , dried and stirred mechanically with 100.0 cm of saturated sodium hydrogen carbonate to remove unreacted acid chloride, then the product was filtered and washed with cold water . The product was recrystallized from a mixture of benzene and petroleum ether, yield 18.0 g (62%) m.p 177.5°C .
coci o I + fo I O°CEther + HC1 NaHCO,
2.1.3 Preparation of N-phenyl- N-o-bromobenzohydroxamic Acid. Reagents: (i ) o-bromobenzoic acid , A.R.,(B.D.H.) (ii ) Thionyl chloride (redistilled) A.R., (H.W). (iii ) Sodium hydrogen carbonate A.R. (H.W) (iv) Diethyl ether A.R., (H.W) ( v ) Petroleum ether A.R. 40-60°C (B.D.H.) (vi ) Benzene, A.R.(H.W).
2.1.3.1 Preparation of fi-phenylhydroxylamine: [3-phenylhydroxylamine was prepared as in 2.1.1.1.
39 2.1.3.2. Preparation of o-bromobenzoyl chloride ~ : 20.0 g (0.1 mol) of o-bromobenzoic acid were refluxed with 25.0g(0.21 mol) of redistilled thionyi chloride and the procedure was continued as in 2.1.2.1 yield 17.5 g (80%). b.p 123°C (lit 122-124 °C).
COOH Br + SOC1, A fo 1 + SO, + HC1.
2.1.3.3: The Coupling Reaction Between o.bromobenzoyi chloride and [VPhenylhydroxylamine: The ligand was prepared as in 2.1.2.3 yield 20.0 g (68%) .m.p.l22.5°C.
O OH
COC1 H-N-OH C N Rr ± OoC Ether J^ Br >^ +HC1 bl ^ , lot fo NaHUOt
2.1.4. Preparation of P-methyl-N-Phenyl -N-p-bromobenzohydroxamic Acid: Reagents: (i ) P-bromobenzoic acid A.R., (B.D.H.). (ii ) Thionyi chloride A.R., (H.W.) (iii ) P-nitrotoluene A.R. (H.W ) (iv ) Sodium hydrogen carbonate. A.R., (H.W)
40 (v ) Diethyl ether. A.R., (H.W.) (vi ) Petroleum ether A.R., 40-60°C (B.D.H) (vii) Benzene A.R., (H.W.) 2.1.4.1 Preparation of P-methyl-N- phenylhydrxoylamine:
P-methyl-N-phenylhydroxylamine was prepared by the reduction of 27.4 g
(0.2mol) of p-nitrotoluene with zinc dust as in 2.1.1.1. yield 17.2 (70%). m.p.82°C
(lit 83°C)34.
NO,
2Zn + H2O 60-65°C ) NH4C1
2..1.4.2. Preparation of p-bromobenzoyl chloride:
P-bromobenzoyl chloride was prepared as in 2.1.2.1
COOH COC1
41 2.1.4.3 The Coupling Reaction Between p-bromobenzoyl chloride and P-methy- N-Phenylhydroxylamine: The coupling was carried out as in 2.1.2.3. yield 21.7.g (71%) m.p.188- 189°C.
9 OH UUL-1 H-N-OH M +HC1
NaHCO3 Br CM3 Br CH3
2.1.5 Preparation of p-methyl-N-phenyl N-o-bromobenzohydroxamic Acid: 2.15.1 Preparation of p-methyl-N-phenylhydroxylamine: p-methy 1-N-phenylhydroxylamine was prepared as in 2.1.1.1.
N02 H-N-OH
+2Zn+H,0 60.65°C
NH4C1 CH3 CH3
2.1.5.2 Preparation of o-bromobenzoyl chloride:
o.bromobenzoyl chloride was prepared as in 2.1.3.2 yield 18.0 (83%) b.p
(123°C)( lit. 122-124°C).
42 COOH COCl B r ^A_ Br
SOC12 _A [O J +SO2+HC1
2.1.53. The Coupling Reaction Between P-methyl -N-phenyl hydroxylamine and o-bromobenzoyl chloride: The coupling was carried out as in 2.1.2.3. Yield 21.5 g (70%). m.p. 110-
O OH COCl H-N-OH of + I O I O°C Ether | O | [O | + HC1 NaliCOj
2.2 Characterization of The Four Hydroxamic Acids: The ligands prepared were identified by : 2.2.1 Their Melting-Points: Using Mettler melting point determining apparatus the melting points were determined . The data are shown in Table (2)
43 Table(2): Melting points of the four hydroxamic acids:
No Hydroxamic acid Melting point °C 1 N-phenyl-N-p-bromobenzohydoxamic acid 177.5°C
2 N-phenyl-N—o-bromobenzohydroxamic acid 122.5 °C
3 P-methyl-N-phenyl-N- p-bromobenzohydroxamic acid 188-189 °C
4 P-melhyl-N-phenyl-N-o-bromobenzohydroxamic acid 110-112°C
2.2.2 Characteristic Colour Reaction: (i) The chloroform solution with an acidic solution of ferric chloride gave blood red colour in the chloroform layer, (ii) The ligand in chloroform with a solution of vanadium (V) in 3M HC1 gave deep-violet colour in the chloroform layer. 2.2.3. Elemental Analysis: 2.2.3.1 Determination of Nitrogen Content of N-Phenyl-N-p-bromo- henzohydroxamic Acid ( Kjeldhahl Method)' 0.5187g of N-phenyl-N-p-bromobenzohydroxarnic acid was taken in a kjeldhahl flask and digested with 20.0 cm3 concentrated sulphuric acid, 3.5 g of potassium sulphate and 0.17g of mangenese dioxide were added to the flask. The heating was continued until the organic matter was destroyed and the solution became clear. The contents of the flask were cooled, diluted with 50.0 cm3 water and a few anti-pumping granules were added. The excess acid was neutralized by
4-1 4M caustic soda with the aid of litmus paper then excess caustic soda was added. 100.0 cm of 0.0996 M hydrochloric acid were placed in the receiver flask which is adjusted so that the end of the condenser just dipped in the acid solution. The contents of the kjeldhahl flask were heated to boil gently for one hour. Few drops of screened methyl orange were added to the receiver and the excess acid was titrated with 0.0972 M. standard sodium hydroixde " . The volume of sodium hydroxide which neutralized the excess hydrochloric acid was 82.0 cm -..
N % = [ V x M HC|) - (Vx MNa0M ) x 1.4] / Weight of the sample.
were V = volume M = Molarilty N % = [ (100.0 x 0.0996) - ( 82.0 x 0.0972) x 1.4 ] / 0.5187. - 5.10%
0.5351 g of N-phenyl-N-o-bromobenzohydroxamic acid, 0.5098 g of P- methyl-N-phenyl-N-p-bromobenzohydroxamic acid and 0.5360 g of p-methyl-N- phenyl-N-o-bromobenzohydroxamic acid were used for nitrogen content determination as in 2.2.3.1. The data are in Table (3). 2.2.3.2. Determination of Bromine Content of N-phenyl-N-p- bromobenzohydroxamic Acid: 0.5000 g of N-phenyl-N-p-bromobenzohydroxamic acid was fused with 1.0 g of sodium metal in small pyrex tube in the fume chamber. The fusion continued for a long time to make sure that all the excess sodium metal was evaporated. The tube and the contents were heated strongly to redness, then transferred quickly to a small beaker containing 50.0 cm distilled water, the tube
45 was broken down, the beaker and its contents were boiled and filtered. The filter paper was washed with hot water till it is free of bromide.
To the filterate, 5.0 cm3 of concentrated nitric acid and 25.0 cm of 0.1M standard silver nitrate were added. The suspension of silver bromide was filtered, dried and weighted. The percentage of bromine content then calculated 128 Other three hydroxamic acids were treated as in 2.2.3.2, the data are in Table (3).
Table (3): Elemental analysis of the four hydroxamic acids:
No llydioxamie acid % Nitrogen % Bromine content content c F C F 1 N-phenyl-N-p-bromobenzo 5.00 5.10 27.39 27.30 -hydroxamic acid. 2 N-phenyl-N-o-bromobenzo 5.00 4.90 27.39 27.45 hydroxamic acid. 3 P-methyl-N-phenyl-N-p- 4.70 4.77 26.14 26.20 bromobenzohydroxamic acid. 4 P-methyl-N-phenyl-N-o- 4.70 4.74 26.14 26.25 bromobenzohydroxamic acid.
2.2.4. Infrared Spectroscopy: Using perkin Elmer Model 1336.I.R spectrophotometer the characteristic functional groups were determined as in Table (4) and presented in appendices A, B, C and D.
46 Tahle(4): Characteristic infrared absorptions of the four hydroxamic acids:
No Hydroxamic acid Functional group in cm" APP.
O-H C = O C-N N-0 1 N-phenyl-N-p-bromobenzohy 3160 1595 1370 810 A droxamic acid 2 N-phenyl-N-o-bromo- 3120 1650 1390 820 B benzohydroxamic acid 3 P-methy-N-phenyl-N-o-bromo 3100 1610 1370 810 C benzohydroxamic acid. 4 p-methyl-N-phenyl-N-p- 3160 1600 1375 810 D bromobenzohydroxamic acid
2.2.5 Ultra-Violet Absorption: Using Perkin-Elmer Model 550S UV/VIS spectrophotometer maximum absorption of the ligands in chloroform are in Table (5) and presented in appendices E.F.G and H.
47 Table (5): Maximum absorption of the four hydroxamic acids in chloroform using Perkin Elmer uv/vis spectrophotometer:
No HycJroxainic acid Wave Length in nm APP
Tr-7U-*transition Aryl ring of C = O 1 N-phenyl-N-p-bromobenzohy 240 280 E droxamic acid 2 N-phenyl-N-o-bromo- 235 260 F benzohydroxamic acid 3 P-methy-N-phenyl-N-o- 240 260 G bromo benzohydroxamic acid. 4 p-methyl-N-phenyl-N-p- 245 280 H bromobenzohydroxamic acid
48 2.3 Extraction and Colourimetric Determinations of Molybdenum (VI), Cliromium((VI), Iron (III) .Vanadium (V), Cobalt (II) and Cupper (II): Reagents: (i ) 1,2 and 3 M sulphuric acid. (ii ) Buffer solutions ' : Solutions of pH 1.0 and pH 2.0 were prepared from a mixture of 0.2M hydrochloric acid and 0.2M potassium chloride in different proportions. Buffer solutions of pll 3.0, 4.0,5.0,6.0 and 7.0 were prepared using 0.1M citric acid and 0.2 M disodium hydrogen phosphate in different proportions . Buffer solutions of pll 8.0,9.0 and 10.0 were prepared by mixing different volumes of 0.1M boric acid in 0.1M potassium chloride and 0.1 M sodium hydroxide . All buffers were adjusted from time to time with the pH-meter using few drops of either 0.1M hydrochloric acid or 0.1M sodium hydroxide.
2.3.1 Extraction and Analysis of Chromium (VI) : Reagents: (i ) Standard chromium solution (1000 ppm Cr (VI), 2.83 g of potassium
3 dichromate (K2Cr207. A.R. B.D.H) disolved in one dm distilled water. Other concentrations were prepared by appropriate dilution from the stock solution. ( ii ) 1% (w/v) ethanolic solution of 1,5- diphenylcarbazide. (iii ) 0.5% (w/v) of hydroxamic acid solution in chloroform .
-J9 2.3.1.1 Extraction of Chromium (VI) with N-phenyl-N-p- bromobenzohydroxamic acid: 5.0 cm of 20 ppm chromium (VI) solution were pipetted into a series often
3 separatory funnels, to the funnels 1,2 and 3, 20.0 cm of 1M, 2M and 3M H2SO4 were added respectively, to the funnels , 4 and 5, 20.0 cm of a solution of pH 1 and pi I 2 were added respectively, to the remaining funnels 20 .0 cm of buffer solutions of pH 3,4,5, 6 and 7 were added respectively . 25.0 cm3 of N-phenyl -N- p-bromobenzohydroxamic acid in chloroform were added to each of the ten funnels and the separatory funnels were shaken for two minutes. Faint golden yellow colour developed . The aqueous and organic layers were separated for further analysis. 2.3.1.2. Preparation of Standard (Calibration) Curve: A calibration curve of chromium (VI) was prepared by transferring 0.5,1.0,1.5,2.0 and 2.5 cm3 of 10 ppm chromium (VI) solution into a series of 10 cm3 volumetric flasks, 5.0 cm3 of 1M sulphuric acid were added and 1.0 cm3 of ethanolic solution of diphenylcarbazide was introduced, completed to the mark with distilled II2O and left for 4 minutes for complete colour development '. The absorbance was read at 540 nm. Results are in Table (6) and represented graphically in figure (1)
50 Table (6): Calibration curve for Cr (VI) by diphenylcarbazide method:
Concentration of Cr (VI) in ppm Ahsorbance at 540 nm. 0.2 0.084 0.4 0.168 0.6 0.253 0.8 0.336 1.0 0.421 0.4-
§ 0.3 o
1) O 0.2-
o en
0.1-
0.0 I I i I i| I I I | i 0.0 0.2 0.4 0.6 0.8 1.0 Concentration [ppm]
Fig (I): Calibration curve of Cr(VI) for the extraction with the four hydroxamic acid prepared.
52 2.3.1.3 Determination of Chromium (VI) in the Aqueous Layer By Diphenylcarbazide Method: 1.0 cm of the aqueous layers separated in 2.3.1.1 were transferred to a series of 10 cm volumetric flasks. The chromium (VI) detemination was carried out as in 2.3.12. Results are in Table (7). % Extracted (Recovery) was plotted against the acid molarity (M) and the pH values as in figures (2) and (3) respectively. 2.3.1.4 Determination of Chromium(VI) in the Organic Layer by Diphenylcarbazide Method: The organic layers were stripped by three (10.0,10. 0 and 5.0 cm3) portions of 0.5 M NaOH with vigorous shaking for two minutes each. 1.0 cm of the basic solutions were transferred to a series of 10 cm volumetric flasks. The chromium (VI) determination was carried out as in 2.3.1.1 Results are in Table (7). The same procedure for the extraction of chromium (VI) was carried out by 0.5% w/v N-phenyl-N-o-bromobenzohydroxamic acid , P-methyl- N-phenyl-N-p-bromobenzohydroxamic acid and P-methyl-N-phenyl-N-o- bromobenzohydroxamic acid in chloroform and the same colourimetric analysis of chromium (VI) was carried out with visible spectroscopy as in 2.3.1.1. Results are in Tables ,8,9 and 10 respectively and represented graphically in figures (2) and (3). The maximum recovery of Cr (VI) with the four hydroxamic acids is represented in Table (11). Table (7): Percent extraction of Cr(VI) with 0.5 w/v N-phenyl -N-p- bromobenzohydroxamic acid:
M Abs.aq A a mount %Remaining Abs. or Amount in % Rec. in aq. in aq. or ( ug) (MS) 1 0.007 0.16 4.00 0.162 3.84 96.00 2 0.012 0.28 7.00 0.154 3.66 93.00 3 0.014 0.33 8.20 0.152 3.57 91.70 pi I Abs.aq A amount %Remaining Abs. or Amount in % Rec. in aq. in aq. or(ug) (US) 1 0.050 1.20 30.00 0.116 2.76 70.00 2 0.111 2.60 66.00 0.058 1.38 35.00 3 0.133 3.10 79.00 0.036 0.85 22.50 4 0.145 3.40 86.00 0.024 0.60 14.00 5 0.111 3.60 90.00 0.016 0.38 10.00 6 0.155 3.70 92.20 0.013 0.30 7.75 7 0.155 3.70 92.20 0.013 0.30 7.75 when Abs.aq. = Absorbance of aqueous layer. Abs.or. = Absorbance of organic layer. Rec. = Recovery ( Extraction) .
54 (8)i Perceiit extraction of Cr(VI) with 0.5 w/v N-phetiy] -N-o- bromobenzohydroxamic acid:
M Abs.aq Aamount %Remaining Abs. or Amount in % Rec. in aq. in aq. or( \ig) (Hg) 1 0.00 0.00 0.00 0.163 3.87 97.00 2 0.008 0.19 4.70 0.154 3.66 95.00 3 0.012 0.28 7.10 0.153 3.64 91.00
PII Abs.aq Aamount %Remaining Abs. or Amount in % Rec. in aq. in aq. J or(ng) (HB) 1 0.071 1.68 42.20 0.095 2.26 56.50 2 0.108 2.50 64.20 0.062 1.47 36.80 3 0.112 3.18 80.00 0.033 0.82 20.00 4 0.147 3.49 87.40 0.020 0.47 11.90 5 0.147 3.49 87.40 0.020 0.47 11.90. 6 0.147 3.49 87.40 0.020 0.47 11.90 7 0.156 3.71 92.80 0.013 0.30 7.00 Table (9): Percent extraction of Cr(VI) with 0.5 w/v P-methyl- N-phenyl -N- p- bromobenzohydroxamic acid:
M Ahs.aq Auni aunt %Remainhig Abs. or Amount in % Rec. in aq. in aq. or( jig) (MB) 1 0.088 2.0' 15.00 0.083 1.97 49.40 2 0.124 2.9 37.80 0.046 1.09 27.30 3 0.135 3.2 80.30 0.033 0.78 19.60
PII Ahs.aq Aumount %Reniaining Abs. or Amount in % Rec. in aq. in aq. or(ng) (HB) 1 0.080 1.88 47.00 0.087 2.07 51.70 2 0.096 2.28 57.10 0.070 1.66 41.60 3 0.109 2.63 65.00 0.058 1.37 35.00 4 0.125 2.9 74.40 0.046 1.09 27.30 5 0.125 2.9 74.40 0.045 1.07 26.70 6 0.130 3.0 77.00 0.041 0.95 23.80 7 0.135 3.2 80.30 0.033 0.78 19.60
56 Table (10): Percent extraction of Cr(VI) with 0.5 w/v P-mefhyl- N-phenyl - N-o- bromobenzohydroxamic acid:
M Abs.aq Aamount %Remuining Abs. or Amount in % Rec. in aq. in aq. (Mg) 1 0.000 0.00 0.00 0.166 3.95 98.70 2 0.000 0.00 0.00 0.166 3.95 98,70 3 0.004 0.09 2.30 0.162 3.85 96.30 pll Abs.aq Aamount %Remaining Abs. or Amount in % Rec. in aq. in aq. or(ug) (MB) 1 0.093 2.20 55.00 0.076 1.80 45.00 2 0.116 2.76 69.00 0.054 1.20 32.00 3 0.153 3.64 91.00 0.016 0.38 9.50 4 0.153 3.64 91.00 0.016 0.38 9.50 5 0.153 3.64 91.00 0.016 0.38 10.00 6 0.167 3.97 99.30 0.001 0.03 0.00 7 0.167 3.97 99.30 0.001 0.03 0.00
Table (11): The maximum recovery of Cr (VI) with the four hydroxamic acids: Hyriruxamic acid PH M %Rec N-phenyl-N-p-bromobenzohydroxamic acid - 1 96.00 N-phenyl-N-o-bromobenzohydroxamic acid - I. 97.00 P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid 1 - 51.00 P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid - 1 98.70
57 100-j —•—a 98- —•—b —A—c 96- —•—d
94-
92-
90*
50-
40-
30-
20-
10-
0 I i Ml M2 M3 M/H,SO,
Fig (2): Extraction curves showing distribution of Cr(Vl) as a function of the acid molarity for: (a) N-phenyl-N-p-bromobenzohydroxamic acid. (b) N-phenyl-N-o-bromobenzohydroxamic acid. (c) P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid. (d) P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid. (0.5% w/v solution in chloroform).
58 70-
60-
50-
40-
30-
20-
10-
0
Fig (3): Extraction curves showing distribution of Cr(VI) as a function of the pH for: (a) N-phenyl-N-p-bromobenzohydroxarnic acid. (b) N-phenyl-N-o-bromobenzohydroxamic acid. (c) P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid. (d) P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid. (0.5% w/v solution in chloroform).
59 2.3.2 Extraction and Analysis of Molybdenum (VI) : Reagents: ( i) Standard molybdenum (VI) solution 1000 ppm molybdenum (VI)
3 (1.84 g of (NH4)7 MoO24 .4H2O. BDH Analar Grade dissolved in dm distilled water). Other concentrations were prepared by appropriate dilution from the stock stolution. (ii ) 1% w/v potassium thiocyanate (B.D.H Reagent) ( iii ) 10% w/v stannous chloride (B.D.II Reagent) (iv ) Di-isopropyl ether (B.D.PI Reagent) ( v ) 0.5% w/v hydroxamic acid solution in chloroform. 2.3.2.1. Extractionof Molybdenum (VI) with N-phenyl-N-p- bromobenzohydroxamic Acid. 5.0 cm from 100 ppm molybdenum (VI) solution were transferred to 25 cm volumetric flasks and diluted to the volume with the solutions of pHl and pH 2 and buffer solutions ranging from pi I 3 to pH 10. The solutions were transferred to separator)' funnels and extracted with an equal volume (25.0 cm3) of N-phenyl- N-p-bromobenzohydroxamic acid in chloroform, with vigorous shaking for two minutes . No colour observed. The two layers were separated for further analysis. 2.3.2.2. Preparation of Standard (Calibration) Curve: Solutions containing 0, 1,2.,3,4 and 5 ppm molybdenum (VI) were prepared by pipetting 0, 2.5 , 5, 7.5, 10 and 12.5 cm" of the 10 ppm molybdenum (VI) solution into six 100 cm"' separatory funnels. 2.0 cm" of concentrated sulphuric acid, 1.0 cm"1 of 1 % ferrous sulphate and 3.0 cm3 of 10 % potassium thiocyanate solution were added , after gentle shaking , 3.0 cm of 10 % stannous chloride souliion were introduced, bringing the total volume to 25 cm with distilled water
60 and extracting the complex with three (10.0, 10.0 and 5.0 cm' ) portions of di-iso- propyl ether . The extracts were combined , poured through afilter paper in small funnel to remove water droplets into a 25 cm volumetric flask and completed to the mark with the same solvent. The absorbances of the solutions were measured at 465 nin in 1-cm cell. Results are in Table (12) and represented graphically in figure (4).
Table (12): Calibration Curve for Mo (VI) by thiocyaiiate colonrimetric methods.
Concentration of Mo(VI)in pprn Absorbance of 460 nin 1.0 0.152 2.0 0.301 3.0 0.456 4.0 0.610 5.0 0.760 6.0 0.915
61 1.0 i
0.8-
52 0.6- a
0.4- o in
0.2-
0.0 0 12 3 4 5 6 Concentration [ppm]
Fig (4): Calibration curve of Mo(VI) for the extraction with the four hydroxainic acid prepared.
62 2.3.2.3. The Determination of Molybdenum (VI) in the Aqueous Layer :
5.0 cm3 of the aqueous solutions were transferred to a series of 100 cm separatory funnels. The molybdenum (VI) determination was carried out as in 2.3.2.2. Results are in Table (13). % Exatraction (Recovery) was plotted against the pH values as in figure (5). 2.3.2.4. The Determination of Molybdenum (VI) in the Organic Layer: The organic layers were stripped by three portions (10.0,10.0 and 5.0 cm ) of 0.5 M NaOH with vigorous shaking for two minutes each. 5.0 cm of the basic solutions were transferred to a series of 100 cm separatory funnels. The molybdenum (VI) determination was carried out as in 2.3.2.2. Results are in Table (13). The same procedure for the extraction of molybdenum (VI) was carried out with 0.5% w/v N-phenyl-N-o-bromobenzohydroxamic acid, p-methyl- N-phenyl-N-p-bromobenzohydroxamic acid and p-methyl-N-phenyl-N-o- bromobenzohydroxamic acid in chloroform and the same colorimetric analysis of molybdenum (VI) was carried out with visible spectroscopy as in 2.3.2.2. Results are in Tables (14,15 and 16) and represented graphically in figure (5). The maximum recovery (extraction) of molybdenum (VI) with the four hydroxamic acids is represented in Table (17).
63 Table (13): Percent extraction of Mo(Vl) with 0.5% w/v N-phenyl -N-p- bromobenzohydroxamic acid in chloroform.
pll Abs.aq Aamount %Rernaining Ahs. or Amount in % Rec. in aq. aq. or( jag) (Pg) 1 0.060 9.80 9.80 0.529 87.00 87.00 2 0.080 13.10 13.10 0.508 83.50 83.50 3 0.110 18.10 18.10 0.484 79.60 79.60 4 0.122 20.00 20.00 0.470 77.30 77.30 5 0.324 53.20 53.20 0.275 45.20 45.20 6 0.366 60.20 60.20 0.234 38.40 38.40 7 0.504 82.00 82.00 0.096 15.70 15.70 8 0.540 88.80 88.80 0.060 •' 10.00 10.00 9 0.540 88.80 88.80 0.060 10.00 10.00 10 0.540 88.80 88.80 0.060 10.00 • 10.00
Table (14): Percent extraction of Mo(VI) with 0.5% w/v N-phenyl -N-o- bromobenzohydroxamic acid in chloroform.
pH Abs.acj Aamount %Remaining Abs. or Amount in % Rec. in aq. aq. or( fig) (Mg) 1 0.034 5.60 5.60 0.564 92.70 92.70 2 0.036 6.00 6.00 0.567 93.20 93.20 3 0.035 5.70 5.70 0.563 92.50 92.50 4 0.039 6.40 6.40 0.569 93.50 93,50 5 0.039 6.40 6.40 0.564 92.70 92.70 6 0.040 6.50 6.50 0.467 93.20 93.20 7 0.456 75.00 75.00 0.146 24.00 24.00 8 0.475 78.00 78.00 0.126 20.70 20.70 9 0.510 83.80 83.80 0.090 14.80 14.80 10 0.510 83.80 83.80 0.090 14.80 14.80
64 Table (15) : Percent extraction of Mo(VI) with 0.5% vv/v P- methy -N-phenyl- N-p- bromobenzohydroxamic acid in chloroform. pll Abs.aq Aamount %Remaining Abs. or Amount in % Rec. in aq. aq. or(^g) (HB) 1 0.144 23.70 23.70 0.451 74.20 74.20 2 0.150 24.70 24.70 0.445 73.20 73.20 3 0.150 24.70 24.70 0.446 73.30 73.30 4 0.186 30.50 30.50 0.413 68.00 68.00 5 0.300 49.30 49.30 0.297 49.00 49.00 6 0.456 75.00 75.00 0.143 23.50 23.50 7 0.510 83.90 83.90 0.094 15.50 15.50 8 0.541 89.00 89.00 0.061 10.00 10.00 9 0.552 90.80 90.80 0.055 9.00 9.00 10 0.552 90.80 90.80 0.055 9.00 9.00
Table (16) : Percent extraction of Mo(VI) with 0.5% w/v P-methyl- N-phenyl N -o- bromobenzohydroxamic acid in chloroform.
pi I Abs.aq Aamount %Remaining Abs. or Amount in % Rec. in aq. aq. or( fig)
1 0.091 15.00 15.00 0.515 84.70 84.70 2 0.091 15.00 15.00 0.513 84.30 84.30 3 0.120 20.00 20.00 0.480 79.00 79.00 4 0.130 21.40 21.40 0.470 78.20 78.20 5 0.260 42.70 42.70 0.348 57.20 57.20 6 0.570 93.70 93.70 0.030 5.00 5.00 7 0.576 94.70 94.70 0.030 5.00 5.00 8 0.576 94.70 94.70 0.030 5.00 5.00 9 0.576 94.70 94.70 0.030 5.00 ' 5.00 10 0.576 94.70 94.70 0.030 5.00 . 5.00
65 Table (17): The maximum recovery of Mo (VI) with the four hydroxamic acids.
Hydro.xarnic acid PH % Recovery N-phenyl -N-p-bromobenzohydroxamic acid 1 87.00 N-phenyl -N-o-bromobenzohydroxamic acid 1 97.80 P-melhyl-N-phenyl-N-p-bromobenzohydroxamic acid 1 74.20 P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid 1 84.70 100-1
90-
80-
70-
60-
50- w 40-
30-
20-
10- • vN 0-
i 0 2 4 8 10 pH
Fig (5): Extraction curves showing distribution of Mo(VI) as a function of the pH for: (a) N-phenyl-N-p-bromobenzohydroxamic acid. (b) N-phenyl-N-o-bromobenzohydroxamic acid. (c) P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid. (d) P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid. (0.5% w/v solution in chloroform).
67 2.3.3. Extraction and Analysis of Iron (III) : Reagents
(i) Standard ferric solution, (1000 ppm Fe (111 ), 8.64 g (NH4)2 FeSO4 12 H2O dissolved in 100.0 cm3 of distilled water, 10.0 cm3 of concentrated hydrochloric acid were added and the volume was completed to dm3 with distilled water).Other concentrations were prepared by appropriate dilution from the stock solution. (ii) Potassium persulphate 2% w/v in aqueous solution, (Freshly prepared and stored in a refrigerator for few days). (iii) Potassium thiocyanate, 20% w/v in aqueous solution. (iv) (1:1) Isobutyl alcohol and carbon tetrachloride. (v) 0.5% w/v hydroxamic acid solution in chloroform.
2.3.3.1. Extraction of Iron(III) with N-phenyl-N-p-broinobenzohydroxamic acid. 5.0 cm3 from 100 ppm Fe (III) solution were transferred to 25 cm3 volumetric falsks and extraction was carried out as in 2.3.1.1. Blood-red colour was observed, the two layers were separated for further analysis . 2.3.3.2 The standard (Calibration) Curve: 0.0, 2.5, 5.0, 7.5, 10.0 and 12.5 cm3 of 10 ppm Fe (III) solution, 20.0 cm3 of distilled water , 5.0 cm of concentrated hydrochloric acid , 1.0 cm3 of 2% w/v potassium persulphate and 10.0 cm of 20 % w/v potassium thiocyanate were tranferred to the separator}' funnels successively. Few drops of 0.005 M potassium permanganate were added . The solutions were extracted wtih three (10.0, 10.0 and 5.0 cm3) portions of (1:1) isobutyl alcohol and carbon tetrachloride, with vigorous shaking for two minutes each. The organic layers were combined through a filter paper to remove water droplets into 25 cm
68 volumetric ilasks. The absorbances were measured at 485 nm using 1- cm cell. Results are in Table (18) and represented graphically in figure (6).
Table (18) : Calibration curve for Fe (III) by thiocyanate colourimetric method.
Concentration in ppm Absorbance at 485 nm 1 0.165 2 0.329 3 0.502 4 0.663 5 0.833
69 l.O-i
0.8-
oo 0.6-
O 0.4- o
0.2-
0.0 0 12 3 4 5 Concentration [ppm]
Fig (6): Calibration curve of Fe(IlI) for the extraction with the four hydroxamic acid prepared.
70 2.3.3.3. The Determination of Iron (III) in the Aqueous Layers: From the aqueous layers 2.5 cm were transferred to a series of 100 cm3 separator)' funnels. The analysis was carried out as in 2.3.3.2. Results are in Table (19). % extracted was plotted against the molarities and the pH values as in figure (7) and (S) respecrhely. 23.3.4. The Determination of Iron (III) in the Organic I.avers: The organic layers were stripped by three ( 10.0, 10.0 and 5.0 cm3) portions of 2M H2SO4 with vigorous shaking for two minutes each. 2.5 cm1 of Ihe acidic solutions were transferred to n series of 100 ctiV separatory funnels. The iron (III) determination was carried out as in 2.3.3.2 Results are in Table (19). The same procedure lor the extnicuon otkvm vUV) wtfhN-p\\e\\\VK^v bromobenzohydroxamic acid , P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid and P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid in chloroform and the same colorimetric analysis of iron (III) were carried out as in 2.3.3.2. Results are in Tables (20,21 and 22) respectively, and represented graphically in. fugures (7) and ( 8). The maximum recovery of Fe (III) with the four hydroxamic acids is represented in Table (23).
71 Table (19): Percent extraction of Fe (HI) with 0.5 % w/v N-phenyl-N-p- bromobenzohydroxamic acid in chloroform :
M Abs.aq Amount in %Rcmaining Abs. or Amount in % Rcc. aq. aq. orftig) 1 0.238 36.00 72.00 0.094 14.00 28.00 2 0.266 40.30 80.60 0.063 9.50 19.00 3 0.332 50.00 100.00 0.000 0.00 0.00 pll Abs.aq Amount in %Kcmaining Abs. or Amount in % Rcc. nq. orftig) 1 0.208 31.50 63.00 0.123 18.60 37.00 2 0.182 27.50 55.00 0.150 22.70 45.00 3 0.122 18.40 37.00 0.205 31.00 62.00 4 0.091 13.70 27.50 0.244 36.90 73.90 5 0.104 15.70 31.50 0.226 34.20 68.40 6 0.310 46.90 94.00 0.023 3.40 6.90 7 0.306 465.30 92.70 0.026 3.90 7.80
Table (20): Percent extraction of Fe (III) with 0.5 % w/v N-phenyl-N-o- bronioben/ohydroxainic acid in chloroform:
M Abs.aq Amount in "/oRcmaiuin^ Abs. or Amount in % Rcc. aq. aq. or (HB) 1 0.297 45.00 90.00 0.033 5.00 10.00 2 0.316 47.80 95.70 0.016 2.40 4.80 3 0.331 50.00 100.00 0.00 0.00 0.00 pi I Abs.aq Amount in % Remaining Abs. or Amount in % Rcc. aq- (ng) -.«]. or frig) 1 0.304 46.00 92.00 0.028 4.00 . 8.00 2 0.227 34.30 68.70 0.106 16.00 32.00 3 0.138 20.90 41.80 0.194 29.30 58.70 4 0.094 14.20 28.00 0.235 35.60 71.20 5 0.138 20.90 41.80 0.192 29.00 58.10 6 n 0.217 32.80 65.70 0.111 16.60 33.30 7 0.212 32.10 64.00 0.115 17.40 34.80
T). Table (21): Percent extraction of Fe (III) with 0.5 % w/v P-methyl N- phenyl-N-p- bromobenzohydroxamic acid in chloroform:
M Abs.aq Amount in %Remaining Abs. or Amount in % Rec. aq. aq. or(^g) 1 0.311 ' 47.00 94.00 0.020 3.00 6.00 2 0.332 50.00 100.00 0.000 0.00 0.00 3 0.287 43.40 86.90 0.046 6.90 13.90 PH Abs.aq Amount in %Remaining Abs. or Amount in % Rec. aq. aq. or((.ig) 1 0.262 39.60 79.40 0.070 10.50 21.00 2 0.174 26.30 52.70 0.157 23.70 - 47.50 3 0.172 26.00 52.00 0.159 23.60 47.20 4 0.172 26.00 52.00 0.159 23.60 . 47.20 5 0.100 15.00 30.00 0.230 34.80 69.60 6 0.185 28.00 56.00 0.146 22.00 44.00 7 0.185 28.00 56.00 0.146 22.00 44.00
Table (22): Percent extraction of Fe (III) with 0.5 % w/vP-methyl -N- phenyl-N-o- bromobenzohydroxamic acid in chloroform:
M Abs.aq Amount in %Remaining Abs. or Amount in % Rec. aq. aq. or(^xg) 1 0.292 44.20 88.40 0.041 6.20 12.40 2 0.297 45.00 90.00 0.036 5.00 10.00 3 0.331 50.00 100.00 0.00 0.00 0.00 pll Abs.aq Amount in %Rernaining Abs. or Amount in .% Rec. aq. aq. or((|ig) 1 0.215 32.50 65.00 0.117 17.70 35.40 2 0.215 32.50 65.00 0.117 17.70 35.40 3 0.133 20.10 40.00 0.198 30.00 60.00 4 0.110 16.50 33.00 0.220 33.30 66.60 5 0.119 18.00 36.00 0.211 31.90 63.90 6 0.230 34.80 69.00 0.103 15.50 31.00 7 0.240 36.60 72.70 0.090 13.50 27.00
73 Table (23): The maximum recovery of Fe (III) with the four hydroxamic acids.
Hydroxamic acid pli M %Rec N-phenyl-N-p-bromobenzohydroxamic acid 4 - 73.90 N-phenyl-N-o-bromobenzohydroxamic acid 4 - 71,20 P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid 5 - 69.60 P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid 4 - 66.60
74 —•—a -•—b 30- A A
—T—d
20- M,
•
10-
0-
i > i • Ml M2 M3
M/H2SO4
Fig (7): Extraction curves showing distribution of Fe(IIl) as a function of the acid molarity for: (a) N-phenyl-N-p-brornobenzohydroxamic acid. (b) N-phenyl-N-o-bromobenzohydroxamic acid. (c) P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid. (d) P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid. (0.5% w/v solution in chloroform).
75 90-| • a 80- • b c 70- d 60-
50-
40-
30-
20-
10-
0 r 0 6 pH
Fig (8): Extraction curves showing distribution of Fe(III) as a function of the pH for: (a) N-phenyl-N-p-bromobenzohydroxamic acid. (b) N-phenyl-N-o-brornobenzohydroxamic acid. (c) P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid. (d) P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid. (0.5% w/v solution in chlorofonn).
76 2.3.4. Extraction and Analysis of Vanadium (V) : Reagents: (i) Standard vanadium solution 1000 ppm V(V), 2.2948 g ammonium
metavanadate (NH4VO3), A.R dissolved in one dm distilled water. Other concentrations were prepared by appropriate dilution from the stock solution, (ii) Concentrated hydrochloric acid, (A.R) Sp.G. 1.18 (H.W). (iii) 0.001M potassium permanganate ,(A.R). (II.W.). (iv) 0.5 % w/v hydroxamic acid in chloroform, (v) 0.5 % w/v N-phenyl-N-benzohydroxamic acid in chloroform . 2.3.4.1 Extraction of Vanadium (V) with N-phenyl-N-p-
bromobenzohydroxamic acid: 5.0 cm portions of 100 ppm vanadium (V) solution were pipetted into a series of 25 cmJ volumetic flasks. To funnels 1,2 and 3 .20.0 cm of 1M , 2M and
3M H2S0.4 were added respectively, to funnels 4 and 5 a solution of pH 1 and pH 2 were added respectively, to the remaining funnels 20.0 cm of buffer solutions ranging from pi I 3 to pH 7 were added respectively . The solutions were transferred to a series of 100 cm3 separatory funnels , few drops of 0.001M potassium permanganate solution were added to each funnel till the solution became faint pink in colour to ensure that all the vanadium was in the maximum oxidation state. 25.0 cm of N-phenyl-N-p-bromobenzohydroxamic acid in chloroform were added to each of the ten funnels and the mixtures were shaked gently for two minutes. Redish-violet colour was observed. The two layers were separated for further analysis .
77 2.3.4.2 The Standard (Calibration) Curve: Solutions containing 0,1,2,3,4 and 5 ppm vanadium were prepared by pipetting 0.0 ,0.5, 1.0, 1.5 and 2.5 cm3 of 25 cm3 volumetric flasks. Few drops of 0.001M potassium permanganate were added to each till a faint pink colour persists. 11.1 cm3 of concentrated hydrochloric acid were added to each volumetric flask and completed to the mark with distilled water. All solutions were 5 M with respect to hydrochloric acid. The contents of the flasks were transferred quantitatively to a series of 100 cm separatory funnels. 25.0 cm of 0.5 % N-phenyl-benzohydroxamic acid were added to each separatory funnel, shaked gently for two minutes and the organic layers were separated into a series of 25 cm3 volumetric flasks. The absorbances were measured at 520 nm . Results are in Table (24) and represented graphically in figure (9).
Table (24): Calibration curve for V(V) by N-phenyl-N-benzohydroxamic acid colourimetric method.
Concentration in ppm Absorbance at 520 nm 1 0.085 2 0.172 3 0.259 4 0343 5 0.435
78 0.4-
o
6 u 0.2-
0.0 0 12 3 4 5 Concentration [ppm]
Fig (9): Calibration curve of V(V) for the extraction with the four hydroxamic acid prepared.
79 2.3.4.3 The Determination of Vanadium (V) in the Aqueous Layers: 5.0 cm3 of each aqueous layer were transferred to seperatory funnels and the analysis was carried out as in 2.3.4.2. Results are in Table (25) . % extracted were plotted against the molarities and the pH values as in figures (10) and (11) respectively. 2.3.4.4. The Determination of Vanadium (V) in the Organic Layers: The organic layers were stripped by three (10.0, 10.0 and 5.0 cm ) portions of 0.5 M. NaF with vigorous shaking for two minutes each 5.0 cm3 of the basic solutions were transferred to a series of 100 cm3 separatory funnels. The vanadium (V) determination was carried out as in 2.3.4.2. The same procedure for the extraction of vanadium (V) was carried out by N-phenyl-N-o-bromobenzohydroxamic acid , P-methyl-N-phenyl-N-p- bromobenzohydroxamic acid and P-methyl-N-phenyl-N-o- bromobenzohydroxamic acid in chloroform, and the same colorimetric determination of vanadium (V) was carried out with visible spectroscopy as in 2.3.4.2. Results are in Tables (26,27 and 28) respectively and represented graphically in figures (10 ) and (11). The maximum recovery of vanadium ( V) with the four hydroxamic acid is represented in Table (29).
80 Table (25): Percent extraction of V (V) with 0.5 % w/v N-phenyl-N-p- bromobenzohydroxamic acid in chloroform :
M Abs.aq %Remaining Abs. or % Amount in % Rec. a(j. Stripped or(ng) 1 0.068 20.00 0.082 24.00 56.00 80.00 2 0.068 20.00 0.082 24.00 56.00 • 80.00 3 0.034 10.00 0.093 27.00 63.00 90.00 pll Abs.aq %Remaining Abs. or % Amount in % Rec. aq. Stripped or(ng) 1 0.024 7.00 0.095 27.60 65.40 93.00 2 0.051 15.00 0.087 25.00 60.00 85.00 3 0.068 20.00 0.082 24.00 56.00 80.00 4 0.155 45.00 0.058 17.00 38.00 55.00 5 0.153 44.00 0.059 17.00 39.00 56.00 6 0.187 54.00 0.047 13.60 32.40 46.00 7 0.220 64.00 0.037 10.00 26.00 36.00
Table (26): Percent extraction of V (V) with 0.5 % w/v N-phenyl -N-o- bromobenzohydroxamic acid in chloroform:
M Abs.aq %Remaining Abs. or % Amount in % Rec. aq. Stripped or(ng) 1 0.095 27.60 0.077 22.40 50.00 72.40 2 0.095 27.60 0.077 22.40 50.00 72.40 3 0.051 15.00 0.090 26.00 59.00 85.00 PH Abs.aq %Remaining Abs. or % Amount in % Rec. aq. Stripped or(ng) 1 0.034 10.00 0.095 28.00 62.00 - 90.00 2 0.078 22.60 0.082 23.80 54.00 77.40 3 0.153 44.00 0.058 16.80 39.00 55.50 4 0.203 59.00 0.041 12.00 29.00 41.00 5 0.277 80.50 0.020 5.80 14.20 20.00 6 0.300 87.00 0.013 3.70 9.30 13.00 7 0.306 89.00 0.011 3.00 8.00 11.00
8! Table (27): Percent extraction of V (V) with 0 ,5 % w/v P-methyl- N-phenyl- N-p- bromobenzohydroxamic acid in chloroform:
M Abs.aq %Remaining Abs. or Amount in % Rec. aq. Stripped oi-(|.ig) 1 0.102 30.00 0.072 21.00 49.00 70.00 2 0.102 30.00 0.072 21.00 49.00 70.00 3 0.095 27.90 0.076 22.30 49.70 72.0 pll Abs.aq %Remaining Abs. or % Amount in % Rec. aq. Stripped or(ng) 1 0.081 23.50 0.078 22.80 53.00 76.00 2 0.204 59.30 0.042 12.20 27.00 40.00 3 0.227 65.90 0.034 9.70 23.20 33.20 4 0.227 65.90 0.034 9.70 23.20 • 33.20 5 0.255 74.00 0.025 7.50 17.50 25.00 6 0.290 84.00 0.015 4.50 10.50 15.00 7 0.306 89.00 0.010 3.00 7.00 11.00
Table (28): Percent extraction of V (V) with 0.5 % w/vP-methyl N-phenyl- N- o- bromobenzohydroxamic acid in chloroform: M Abs.aq %Remaining Abs. or % Amount in % Rec. aq. Stripped or(fig) 1 0.068 20.00 0.082 24.00 56.00 80.00 2 0.051 15.00 0.087 25.00 60.00 85.00 3 0.050 14.50 0.088 25.50 60.00 85.50 pH Abs.nq %Remaining Abs. or % Amount in % Rec. aq. Stripped or(ng) 1 0.042 12.00 0.090 26.00 58.00 88.00 2 0.068 20.00 0.082 24.00 56.00 80.00 3 0.098 28.00 0.073 21.00 51.00 72.00 4 0.187 54.00 0.047 13.60 33.40 46.00 5 0.204 59.00 0.042 12.00 29.00 41.00 6 0.235 68.00 0.033 9.50 22.50 32.00 7 0.271 78.70 0.021 6.00 16.30 22.30
82 Table (29) : The maximum recovery of V(V) with the four hydroxamic acids:
Hydroxamic acid pH M %Rec N-phenyi-N-p-bromobenzohydroxamic acid 1 - 93.00
N-phenyl-N-o-bromobenzohydroxamic acid 1 - 90.00
P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid 1 — 76.00
P-melhyl-N-phenyl-N-o-bromobenzohydroxamic acid 1 - 88.00
83 90-
W 80
70-
Ml M2 M3
M/H2SO4
Fig (10): Extraction curves showing distribution of V(V) as a function of the acid molarity for: (a) N-phenyl-N-p-bromobenzohydroxamic acid. (b) N-phenyl-N-o-bromobenzohydroxamic acid. (c) P-metfiyl-N-phenyl-N-p-bromobenzohydroxarnic acid. (d) P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid. (0.5% w/v solution in chloroform).
84 100-1
90-
80-
70-
60-
50-
40-
30-
20-
10-
0- T 4 5 pH
;(11): Extraction curves showing distribution of V(V) as a function of the pH for: (a) N-phenyl-N-p-bromobenzohydroxamic acid. (b) N-phenyl-N-o-bromobenzohydroxamic acid. (c) P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid. (d) P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid. (0.5% w/v solution in chloroform).
85 2.3.5 : Extraction and Analysis of Cobalt(ll) : Reagents:
(i) Standard cobalt solution (1000 ppm Co (II), (4.7695 g Go SO4 7H2O) (A.R) dissolved in dm3 distilled water).Other concentrations were prepared by appropriate dilution. (ii) Ammonium thiocyanate A.R. 60% w/v in aqueous solution,
(iii) Sodium pyrophosphate Na_,P2O7. 101120.1% w/v in aqueous solution, (iv) Isoamyl alcohol saturated with ammonium thiocyanate. (v) 0.5% w/v -hydroxamic acid in chlororform. .
2.3.5.1 Extraction of Cobalt (II) with N-pheiiyl-N-p-bromobenzohydoxamic acid: 5.0 cm portions of 100 ppm cobalt (II) solution were pipetted into a series of 25 cm volumetric flasks and extraction was carried out as in 2.3.2.1. 2.3.5.2 The Standard (Calibration )Curve: Solutions containing 0,1,2,3,4,5 and 6 ppm cobalt (II) solution were prepared by pipetting 0.0,1.0,2.0,3.0,4.00,5.0 ,and 6.0 cm3 of the 25 ppm cobalt (II) solution into a series of 25 cm volumetric flasks. 7.5 cm3 of ammonium thiocyanate and 5.0 cm of sodium pyrophosphate were added, bringing the total volume to 25.0 cm with distilled water. The contents of each flask were transferred quantitatively to a series of 100 cm3 separatory funnels,and were extracted with equal volume (25.0 cm' ) of saturated isoamyl alcohol . The absorbances of organic layers were measured at 620 nra using 1- cm cell. Results are in Table (30) and represented graphically in figure (12).
86 Table (30): Calibration curve for Co(II) by colorimetric method.
Concentration in ppm Ahsorbance at 420 nin I 0.029 ? 0.059 3 0.085 4 0.116 5 0.144
87 0.16-1
0.14 -
0.12-
0.10-
0.08-
0.06-
0.04-
0.02 -
0.00- 2 3 4 Concentration [ppm]
Fig (12): Calibration curve of Co(II) for the extraction with the four hydroxamic acid prepared.
88 2.3.5.3 The Determination of Cobalt (II) in the Aqueous Layer: 10.0 cm of each aqueous layer were transferred to 25cm volumetric flask, 10.0 cm1 of ammonium thiocyanate and 5.0 cm" of sodium pyrophosphate were added and the analysis was carried out as in 2.3.5.2. Results are in Table (3 I) and represented graphically in figure (13)
2.3.5.4. The Determination of Cobalt (II) in the Organic Layers: The organic layers were stripped by three (10.0,10.0 and 5.0 cm3) portions of 2M H2SO4 with vigorous shaking for two minutes each . 10.0 cm3 of the acid solutions were transferred to a series of 25 cm3 volumetric flasks and the analysis was carried out as in 2.3.5.2. The same procedure for the extraction of cobalt (II) was carried out with 0.5% w/v N-phenyl-N-o-bromobenzohydroxamic acid, P-methyl-N-phenyl-N-p- bromobenzohydroxamicacid and P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid in chloroform and the analysis was carried out as in 2.3.5.2. Results are in Tables (32,33 and 34) respectively and represented graphically in figure (13) . The maximum recovery of cobalt (II) with the four hydroxamic acids is represented in Table (35). Table (31): Percent extraction of Co(II) with 0.5% w/v N-phenyl -N-p- bromobenzohytlroxamic acid in chloroform.
p" Abs.aq Aamount %Remaitiing Abs. or Amount in % Rec. in aq. aq. or( Lig) U'g) 1 0.175 150.00 75.00 0.057 49.00 24.50 2 0.168 144.80 72.40 0.063 54.30 27.00 3 0.160 137.90 68.90 0.071 61.00 30.50 4 0.160 137.90 68.90 0.071 61.00 30.50 5 0.187 161.00 80.60 0.045 38.70 19.00 6 0.187 161.00 80.60 0.045 38.70 19.00 7 0.097 83.50 41.80 0.133 114.60 57.30 8 0.037 32.00 15.90 0.193 166.30 83.10 9 Turbid - - - - - 10 - - - - -
Table (32): Percent extraction of Co(Il) with 0.5% w/v N-phenyl -N-o- bromobenzohydroxamic acid in chloroform.
pll Abs.aq Aamount % Remain ing Abs. or Amount in % Rec. in aq. aq. or( ng)
1 0.225 194.00 96.90 0.007 6.00 3.00 2 0.200 172.40 86.00 0.034 29.30 14.00 3 0.209 180.00 90.00 0.023 19.80 10.00 4 0.219 188.00 94.00 0.014 12.00 6.00 5 0.207 178.00 89.00 0.026 22.00 11.00 6 0.181 156.00 78.00 0.052 44.00 22.00 7 0.106 91.00 45.00 0.127 109.40 54.70 8 Turbid - - - - - 9 u - - - - - 10 - - - - -
90 Table (33) : Percent extraction of Co(H) with 0.5% w/v P-methyl N-phenyl- N-p- bromobenzohydroxamic acid in chloroform.
p» Abs.aq Aamount %Remaining Abs. or Amount in - % Rec. in aq. aq. or( jig) (Pg) 1 0.225 194.00 97.00 0.007 6.00 3.00 2 0.216 186.00 93.00 0.016 13.70 6.80 3 0.212 182.00 91.00 0.020 17.20 . 8.60 4 0.209 180.00 90.00 0.023 19.80 10.00 5 0.172 148.00 74.00 0.060 51.70 25.80 6 0.180 155.00 77.50 0.052 44.80 22.40 7 0.145 125.00 62.50 0.087 75.00 37.50 8 •0.113 97.00 48.70 0.119 102.50 51.20 9 Turbid - - - - - 10 it - - - - -
Table (34): Percent extraction of Co(II) with 0.5% w/v P-methyl N-phenyl N-o-bromobenzohydroxamic acid in chloroform.
pll Abs.aq Aamount %Remaining Abs. or Amount in % Rec. in aq. aq. or( \xg) (Mg) 1 0.194 167.00 83.60 0.037 32.00 16.00 2 0.196 168.00 84.50 0.034 29.00 14.60 3 .0.194 167.00 83.60 0.037 32.00 16.00 4 0.225 194.00 97.00 0.007 6.00 3.00 5 0.218 188.00 94.00 0.014 12.00 6.00 6 0.169 146.00 73.00 0.063 54.00 27.00 7 0.116 100.00 50.00 0.116 100.00 50.00
8 Turbid - • - - - IC 9 - - - - - u 10 - - - - -
91 Table (35): The maximum recovery of Co(II)) with the four hydroxamic acids.
Hydroxamic acid pll % Recovery
N-phenyl -N-p-bromobenzohydroxamic acid 8 83.10
N-phenyl -N-o-bromobenzohydroxamic acid 7 • 54.70
P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid 8 51.20
P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid 7 50.00
92 90-i
80-
70-
60-
50-
40-
30-
20-
10-
0-
i—'—i—'—i—•—i 0 12 3 4 5 6 7 8 9 10 PH
Fig (13): Extraction curves showing distribution of Co(II) as a function of the pH for: (a) N-phenyl-N-p-bromobenzohydroxamic acid. (b) N-phenyl-N-o-bromobenzohydroxamic acid. (c) P-methyl-N-phenyl-N-p-broinobenzohydroxamic acid. (d) P-methyl-N-phenyl-N-o-bromobenzohydroxainic acid. (0.5% w/v solution in chloroform).
93 2.3.6. Extraction and Analysis of Copper : Reagent:
(i) Standard copper solution (1000 ppm Cu (II), 3.9282 g of CuSO4.5H2O dissolved in dm of distilled water). Other concentrations were prepared by appropriate dilution from the stock solution . (ii) 60% w/v Citric acid in aqueous solution, (iii) l%w/v EDTA in aqueous solution, (iv) 10% v/v ammonium hydroxide solution (v) 0.1 % w/v sodium diethyldithiocarbamate (B.D.H., A.R.) in distilled water, (vi) chloroform. 2.3.6.1. Extraction of Copper(ll) with N-phenyl-N-p-bromobenzohydroxamic Acid. From 100 ppm Cu (II) solution, 5.0 cm were transferred to a series of 25 cm3 volumetric flasks and extraction was carried out as in 2.3.2.1. 2.3.6.2 . The Standard (Calibration) Curve: 0.0,2.50, 5.0 , 7.5, 10.0 and 12.5 cm3 of 10 ppm Cu (II) solution were placed into a series of separator)' funnels , 20.00 cm distilled water , 5.0 cm citric acid (60%) 5.0 cm3 EDTA (1%) and ammonium hydroxide (10 %) until the solution was neutral to litmus were added. 3.0 cm ammonium hydroxide in excess and 10.0 cm sodium diethyldithiocarbamate were introduced. The solutions were extracted with three (10.0, 10.0 and 5.0 cm ) portions of chloroform shaking for two minutes each. The three extracts were combined in a 25 cm volumetric flasks through a filter paper. The absorbances were measured at 433 inn in 1 cm cell. Results are in Table (36) and represented graphically in figure (14).
94 Table (36): Calibration curve for Cu (II) by Sodium diethyldithiocarbamate colourimetric method.
Concentration in ppm Absorbance at 433 nm
1 0.208
2 0.421
3 0.650
4 0.851
5 1.070
95 1.2
1.0-
0.8-
2
0.4-
0.2-
0.0 2 3 4 Concentration [ppm]
Fig (14): Calibration cur\'e of Cu(II) for the extraction with the four hydroxamic acid prepared.
96 2.3.6.3. The Determination of Copper (II) in the Aqueous Layers: From each aqueous layer 5.0 cm' were transferred to a series of separatory funnels. The analysis was carried out as in 2.3.6.2 Results are in Table (37) and represented graphically in Figure (15). 2. 3.6.4. The Determination of Copper (II) in the organic Layer: The organic layer was stripped with three (10.0, 10.0 and 5.0 cm3) portions of 2 M 1USO4 with vigorous shaking for two minutes each. 5.0 cm" of the acid solution were transferred to a series of separatory funnels . The Cu (II) analysis was carried out as in 2.3.6.2. The same procedure for the extraction of Cu (II) was carried out with 0.5% w/v N-phenyl-N-o-bromobenzohydroxamic acid, P-methyl-N-phenyl-N-p- bromobenzohydroxamic acid and P-methyl-N-phenyl-N-o- bromobenzohydroxamic acid in chloroform and the analysis was carried out in 2.3.6.2. Results are in Tables (38,39 and 40 ) respectively and represented graphically in figure (15). The maximum recovery of Cu (II) with the four hydroxamic acid is represented in Table (41).
97 Table (37) : Percent extraction of Cu(II) with 0.5% w/v N-phenyl- N-p- bromobenzohydroxamic acid in chloroform.
pll Abs.aq Aa mount %Remaining Abs. or Amount in % Rec. in aq. aq. or( jjg) (MB) 1 0.805 94.40 94.40 0.042 5.00 5.00 2 0.788 92.40 92.40 0.059 7.00 7.00 3 0.771 90.50 90.50 0.076 9.00 9.00 4 0.636 74.60 74.60 0.212 24.80 24.80 5 0.339 39.40 39.40 0.500 58.60 58.60 6 0.042 4.90 4.90 0.800 93.80 93.80 7 0.212 24.80 24.80 0.630 73.90 73.90
8 Turbid - - - - - • tt 9 - - - - -
10 - - - - -
Table (38) : Percent extraction of Cu(II) with 0.5% vv/v N-phenyl- N-o- bromobenzohydroxamic acid in chloroform.
pll Abs.aq Aa mount %Remaining Abs. or Amount in % Rec. in aq. aq. or( ng) (ng) 1 0.805 94.50 94.50 0.042 5.00 94.50 2 0.760 89.20 89.20 0.085 10.00 89.20 3 0.721 84.60 84.60 0.127 15.00 84.60 4 0.450 52.80 52.80 0.394 46.00 52.80 5 0.102 12.00 12.00 0.737 86.50 12.00 6 0.186 21.80 21.80 0.653 76.60 21.80 7 0.424 49.70 49.70 0.420 49.30 49.70 8 Turbid - - - - - 9 ;t - - - - - 10 it - - - - -
98 Table (39) : Percent extraction of Co(II) with 0.5% w/v P-methyl N-phenyl- N-p- bromobenzoliydroxamic acid in chloroform.
pi I Abs.aq Aa mount %Remaining Abs. or Amount in % Rec. in aq. aq. or( f.ig) (f'g) 1 0.839 98.50 98.50 0.008 1.00 1.00 2 0.762 89.40 89.40 0.085 10.00 10.00 3 0.340 40.00 40.00 0.502 60.00 60.00 4 0.254 30.00 30.00 0.581 68.20 68.20 5 0.127 15.00 15.00 0.700 82.20 82.20 6 0.254 30.00 30.00 0.580 68.20 68.20 7 0.380 44.60 44.60 0.461 54.10 54.10 8 Turbid - - - - - 9 (i - - - - - 10 - - - - -
Table (40): Percent extraction of Co(II) with 0.5% w/v P-methyl N-phenyl- N-o- bromobenzohydroxamic acid in chloroform.
pH Abs.a(| A amount %Remaining Abs. or Amount in % Rcc. in aq. aq. or( f.ig) (Hg) 1 0.840 98.50 98.50 0.008 1.00 1.00 2 0.805 94.50 94.50 0.042 5.00 - 5.00 3 0.780 91.50 91.50 0.068 8.00 8.00 4 0.450 52.80 52.80 0.399 46.80 46.80 5 0.254 29.80 29.80 0.590 69.20 69.20 6 0.170 20.00 20.00 0.670 78.60 78.60 7 0.288 33.80 33.80 0.553 64.90 64.90 8 Turbid - - - - - 9 u - - - - - 10 ti - - - - -
99 Table (41): The maximum recovery of Cu(II) with the four hydroxamic acids.
Hydroxamic acid pll % Recovery N-phenyl -N-p-bromobenzohydroxamic acid 6 93.80
N-phenyl -N-o-bromobenzohydroxamic acid 5 86.50
P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid 5 82.20
P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid 6 78.60
100 100-j
90-
80- a 70- c 60- d 50- b 40-
30
20-
10-
0- r i 0 2 7 8 10 pH
Fig (15): Extraction curves showing distribution of Cu(II) as a function of the pH for: (a) N-phenyl-N-p-bromobenzohydroxamic acid. (b) N-phenyl-N-o-bromobenzohydroxamic acid. (c) P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid. (d) P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid. (0.5% w/v solution in chlorofonn).
[01 2.4. Metal Complexes: 6.0x10" mol of each four hydroxamic acids prepared was dissolved in 25.0 cm3 ethanol in a 100. cm3 quickfit concical flask with stopper and.2.0 x 10"" mol of each metal ions ( Mo (VI), V (V), Cr (VI), Fe (III), Co (II) and Cu (II) in a suitable buffer solution was added, the contents were stirred for 15 minutes and the residue was filtered , recrystallized and dried . The new complexes were identified by elemental analysis and molecular weight determination . Results:
Table (42) : Identification of metal ion complexes of N-phenyl-N-p- bromobenzohydroxamic acid (L):
Complex % Nitrogen % Bromine M.wt Stiochiometric Ratio(M/L) C F c F C F VO,(L) 3.90 3.75 22.3 22.25 358 .350 1:1
CrO2 (L)2 4.20 4.00 24.0 23.80 666 656 1:2 Fe O (L) 3.80 3.70 22.0 21.9 362.8 357 1:1 CO (L), 4.30 4.20 25.0 24.9 640 635 1:2
Cu (L)2 4.30 4.20 22.0 24.6 645.5 641 1:2
MoO2 (L)2 3.90 3.80 22.5 22.35 700 700 1:2
where : C = Calculated. F = Found. M.wt = Molecular weight.
102 Table (43) : Identification of metal ion complexes of- N-phenyl-N-o- bromobenzohydroxamic acid (L): Complex % Nitrogen % Bromine M.wt Stiochiometric Ratio(M/L) c F c F c F VQ(L) 3.90 3.85 22.30 22.25 •358 355 1:1
CrO2(L)2 4.20 4.15 24.90 23.95 666 662 1:2 FeO (L) 3.80 3.75 22.0 21.90 362.8 358 1:1
CO(L)2 4.30 4.20 25.0 24.95 640 637 1:2 1 Cu (L)2 4.30 4.20 24.7 24.65 645.5 640 1:2 MoO2 (L)2 3.90 3.80 22.5 22.40 710 706 1:2
Table (44) : Identification of metal Ion complexes of N-phenyl-N-p- bromobenzohvdroxamic acid:
Complex % Nitrogen % Bromine M.wt Stiochiometric Ratio(M/L) c F c F C F VO,(L) 3.70 3.65 21.5 21.35 372 369 1:1
CTO2(L)2 4.00 3.85 23.00 22.90 694 689 1:2 FeO (L) 3.70 3.55 21.20 21.10 376.8 372 1:1
CO (L2) 4.20 4.20 23.90 23.80 668 665 1:2
Cu (L)2 4.10 4.00 23.60 23.60 673.5 669 1:2 MoO2 (L)2 3.80 3.75 21.55 21.55 738 732 1:2
!03 Table (45) : Identification of metal ion complexes of F-methyl -N-p-phenyl -o-bromobenzohydroxamic acid (L):
Complex % IN'itrogen % Bromine M.wt Stiochiometric Ratio(M/L) C F C F C F
VO2(L ) 3.70 3.60 21.50 24.4 372 370 1:1
Cr O2 (L)2 4.00 3.90 23.00 23.00 694 690 1:2 FeO (L) 3.70 3..70 21.20 21.15 376.8 375 1:1
CO (I.)2 4.20 4.10 23.90 23.85 668 666 1:2 Cu(L)2 4.10 4.00 23.70 23.60 673.5 670 1:2
MoO2 (L)2 3.80 3.75 21.60 21.5 738 735 1:2
104 2.5. Speetrophotometric studies on M+" - hydroxamic acid complexes: 2.5.1. M+n-N-phenyl-N-p-bromobenzohydroxainic acid complexes: Reagents: (i) fvfn = Different concentrations of M'n[Mtn = Cr (VI), V (V),
Fe (III) , Co (II) and Cu (II) (ii) Different concentrations of hydroxamic acids in chloroform
2.$.1.1. Continuous variation method: The composition of M'" - N-phenyl-N-o-bromobenzohydroxamic acid complexes was determined by application of continuous variation method ' A series of solutions were prepaid in which varying proportions of M+n and the ligand were mixed under buffer control, keeping the total concentration constant in which the mole fractions of M n and the ligand were varied from 0.2 to 0.8. Absorbances of the organic extracts were measured against the solvent (chloroform) as a blank. The same procedure was carried out with N-phenyl -N-p-bromobenzohy- droxamic acid, P-melhyl-N-phenyl-N-p-bromobenzohydroxamic acid and p- methyl -N-phenyl -N-o-bromobenzohydroxamic acid. Results are in the following Tables and figures.
105 Table (46): Characteristic colour of hydroxamate complexes in chloroform : Complex Colour of Chloroform Mo (VI)-N-phenyi-N-o-bromobenzohydroxainie acid colourless Mo(VI)-N-" -p- " :> " " u Mo(VI)-p-methyl-N-phenyl-N-o-bromo- benzohydroxamic acid. u Mo(VI)-p- " " -p- "
Cr(Vi) Golden yellow Cr(VI) u a Cr(VI) a u Cr(VI) u u
Fe (III) Blood-red it U Fe (III) Fe (III) cc a Fe (III) a u
V(V) Reddish -violet V(V) (i • a V(V) V(V)
Co (II) Light-Pink Co (II) a u Co (II) u Cu (II) Green Cu (II) (C Li cu (in a u Cu (II) 106 +6 Table(47): Continuous variation method for Cr -N-phenyl-o- bromobenzohydroxamic aci(i system. Solutions 1 2 3 4 5 6 7 Volof(0.01M)Cr(VI)incm3 2 3 4 5 6 7 8 Volof(IM)H2SO4incm- 10 10 10 10 10 10 10 3 Vol of distilled H2O in cm 13 12 11 10 9 8 7 Vol of(0.01M)oftheligand in cm 8 7 6 5 4 3 2 Vol of chloroform added to 17 18 19 20 21 22 23 the ligand in cm" Mole fraction of Cr. M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance of organic layer at 540 nm 0.050 0.071 0.100 0.130 0.081 0.052 0.052 107 +6 Table(48): Continuous variation method for Cr -N-phenyl-N-p- bromobenzohydroxamic acid system. ! Solutions 1 2 3 4 5 6 I 7 i Volof(0.01M)Cr(VI)incm3 2 3 4 5 6 7 8 3 Vol of(IM)H2SO4incm 10 10 10 10 10 10 10 3 VoIofdisti]JedH2Oincm 13 12 11 10 9 8 7 •! Vol of(0.01M)oftheligand in cm" 8 7 6 5 4 3 • • 2 ; Vol of chloroform added to 17 18 19 20 21 22 . 23 the ligand in cm Mole fraction of Cr.(VI) M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance of organic layer at 540 nm 0.052 0.079 0.095 0.153 0.140 0.100 0.084 108 Tab)c(49): Continuous variation method for Cr +6 -P-methyl-N-phenyl-p- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(0.01M)Cr(VI)incm3 2 3 4 5 6 7 8 3 Volof(IM)H2SO4incm 10 10 10 10 10 10 10 ;! Vol of distilled M2O in cm 13 12 11 10 9 8 7 Vol of (0.01 M) of the ligand in cm 8 7 6 5 4 3 2 Vol of chloroform added to 17 18 19 20 21 22 23 the ligand in cm Mole fraction of Cr Vl M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 i Absorbance of organic layer at 540 nin 0.060 0.072 0.090 0.105 0.090 0.070 0.051 109 Tablc(50) : Continuous variation method for Cv'(> -p-mctliyl-N-plicnyl-o- bromoben/ohvdroxiimic acid system. Solutions 1 2 3 4 5 6 7 • V()lor(().01M)Cr(YI)incnV^ -) 3 4 5 6 7 8 3 Volof(IM)II2S().,incm 10 10 10 10 10 10 10. Vol ofdi.stilledH.Oincn^ 13 12 11 10 9 8 • • f': !Vol oi'(().()]M)ofthcligaiul [in cm 8 7 6 5 4 3 2 Vol of chloroform added to 17 18 19 20 21 22 23 :thc ligand in cm' i r • ------ iMole fraclion o('('ru M/Mil. ().?.() 0.30 0.40 0.50 0.60 0.70 0.80 Absorbancc oi"organic layer at 540 nm 0.040 0.041 0.060 0.080 0.060 0.040 0.040 10 +3 Table(51): Continuous variation method for Fe -N-phenyl-N-o- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(lxlO'3M)Fe(III)in 7 3 4 5 6 7 8 1 cm Vol of pi I. 4 in cm -} 2 2 2 2 2 2 3 VolofdistilledH2Oincm 6 5 4 3 2 1 0 Vol of (lxlO'3M) of the ligand in cm 8 7 6 5 4 3 2 Vol of chloroform added to 3 4 5 6 7 8 the ligand in cm Mole fraction of Fe (III) M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance of organic layer at 485 nni 0.640 0.701 0.870 0.691 0.525 0.400 0.400 11 Table(52): Continuous variation method for Fe -N-phenyl-N-p- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(lxlO~3M)l:e(IIl)in 2 3 4 5 6 7 8 cm Vol of pi I. 4 in cm 2 2 2 2 2 2 2 3 Vol of distilled 112O in cm 6 5 4 3 2 1 0 Vol of (IxlO"3M) of the ligand in cm' 8 7 6 5 4 3 2 Vol of chloroform added to 2 3 4 5 6 7 8 the ligand in cm Mole fraction of Fe (III) M/M-i-L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance of organic layer at 485 nm 0.620 0.670 0.832 0.650 0.525 0.400 0.380 112 Table(53): Continuous variation method for Fe+ 3-p-methyl-N-phenyl-N-p- bromobenzoliydroxaniic acid system. Solutions 1 2 3 4 5 6 7 Volof(lxlO'3M)Fe(III)in 2 3 4 5 6 7 8 cm' Vol of pi I. 4 in cm 2 2 2 2 2 2 2 J Vol of distilled H2O in cm 6 5 4 3 2 1 0 Vol of (lxlO"3M) of the ligand in cm" 8 7 6 5 4 3 2 Vol of chloroform added to 3 4 5 6 7 8 the ligand in cm Mole fraction of Fe (III) M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance of organic layer at 485 nm 0.340 0.440 0.605 0.443 0.331 0.200 0.201 113 Table(54): Continuous variation method for Fe+ 3-p-methyl-N-phenyl-N-o- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(lxlO"3M)Fe(lII)in 2 3 4 5 6 7 8 cm Vol of pH. 4 in cm 2 2 2 2 2 2 2 3 Volofdistilled.H2Oincm 6 5 4 3 2 1 0 Vol of (lxlO"3M) of the ligand in cm 8 7 6 5 4 3 2 i Vol of chloroform added to 2 3 4 5 6 7 8 the ligand in cm Mole fraction of Fe (III) M/M+L- 0.20 0.30 0.40 ' 0.50 0.60 0.70 0.80 Absorbance of organic layer at 485 nm 0.501 0.650 0.801 0.640 0.350 0.200 0.205 14 Table(55): Continuous variation method for V7 +' 5 -N-phenyl-N-o- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(5xlO"3M)( V)incm3 ? 3 4 5 6 7 8 Vol of pi 1. 1 in cm 2 2 2 2 2 2 2 3 VolofdistilledH2Oincm 6 5 4 3 2 1 0 Vol of (5xlO"3M) of the ligand in cm 8 7 6 5 4 3 2 Vol of chloroform added to 2 3 4 5 6 7 8 the ligand in cm Mole fraction of V (V) M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance of organic layer at 520 nm 0.225 0.301 0.500 0.631 0.572 6.450 0.400 115 Table(56): Continuous variation method for V7 +~ 5 -N-phenyl-N-p- bromobenzoliydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(5xlO"3M)( V)incm3 i 3 4 5 6 7 8 Vol of pi I. 1 in cm3 2 2 2 2 2 2 2 3 Vol of distilled H2O in cm 6. 5 4 3 2 1 0 Volof (5x!O'3M) of the ligand in cm" 8 7 6 5 4 3 2 Vol of chloroform added to 2 3 4 5 6 7 8 the ligand in cm" Mole fraction of V (V) M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance of organic layer at 520 nm 0.360 0.450 0.510 0.6.1 0.550 0.470 0.401 116 Table(57): Continuous variation method for V ' -p-methylN-phenyl-N-p- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(5xlO"3M)( V)incm3 2 3 4 5 6 7 8 Vol of pH. 1 in cm 2 2 2 2 2 2 2 Vol of distilled H2O in cm 6 5 4 3 2 1 0 Vol of (5xlO"3M) of the ligand in cm 8 7 6 5 4 3 2 Vol of chloroform added (o 2 3 4 5 6 7 8 the ligand in cm Mole fraction of V (V) M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance of organic layer at 520 nm 0.300 0.301 0.452 0.561 0.500 0.421 0.357 17 Table(58): Continuous variation method for V+~ -p-methyl-N-phenyl-N-o- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(5xlO"3M)( V)incm3 2 3 4 5 6 7 8 Vol of pi L 1 in cm 2 2 2 2 2 2 2 3 Vol of distilled H2O in cm 6 5 4 3 2 1 0 Volof (5xI0'3M) of the ligand in cm 8 7 6 5 4 3 2 Vol of chloroform added to 2 3 4 5 6 7 8 the ligand in cm3 Mole fraction of V (V) M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance of organic layer at 520 nm 0.300 0.380 0.450 0.535 0.452 0.350 0.252 in Table(59): Continuous variation method for Co +2 -N-phenyl-N-o- broinobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(.01M)Co+2incm3 ? 3 4 5 6 7 8 Vol of pH 7 in cm' 10 10 10 10 10 10 10 3 Vol of distilled H2O in cm 13 12 11 10 9 8 7 Vol of L(.01M)incm3 8 7 6 5 4 3 . 2 Vol of chloroform added to 17 18 19 20 21 22 23 the ligand in cm3 M.FofCo'*2M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance at 620 nm 0.015 0.036 0.060 0.040 0.030 0.012 0.003 119 Table(60): Continuous variation method for Co(II) -N-phenyl-N-p- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(.01M)Co+2incm3 2 3 4 5 6 7 8 Vol of pH 7 in cm3 10 10 10 10 10 10 10 Vol of distilled H2O in 13 12 11 10 9 8 7 cm Vol of L(.01M)incm3 8 7 6 5 4 3 2 Vol of chloroform added 17 18 19 20 21 22 23 to the ligand in cm' M.FofCo+2M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance at 620 nm 0.022 0.045 0.068 0.050 0.041 0.020 0.010 120 +2 Table(61): Continuous variation method for Co -p-methyl-N-phenyl-N-p- bromobenzohydroxamic acitl system. Solutions 1 2 3 4 5 6 7 i Volof(.01M)CV2incnv' 2 3 4 5 6 7 8 Vol of pH 7 in cm 10 10 10 10 10 10 10 Vol of distilled H2O in cm 13 12 11 10 9 8 7 Vol of L(.01M)incV 8 7 6 5 4 3 2 1 Vol of chloroform added to 17 18 19 20 21 22 23 the ligand in cm M.FofCo+2M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance at 620 nm 0.012 0.030 0.055 0.040 0.025 0.010 0.003 121 Table(62): Continuous variation method for Co +2 -p-methyl-N-phenyl-N-o- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Vol of(.01M)Cof2incm3 2 3 4 5 6 7 8 Vol of pH 7 in cm 10 10 10 10 10 10 10 Vol of distilled .H2O in 13 12 11 10 9 8 7 cm Vol of L(.01M)incm3 8 7 6 5 4 3 2 Vol of chloroform added to 17 18 19 20 21 22 ' 23 the ligand in cm" M.FofCV2M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance at 620 nin 0.011 0.031 0.053 0.040 0.022 0.010 0.004 !22 Table(63): Continuous variation method for Cu +2 -N-phenyl-N-o- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(.OIM)Cu*2incm3 2 3 4 5 6 7 8 Vol of pU 5 in cm 10 10 10 10 10 10 10 3 Vol of distilled .H2O in cm 13 12 11 10 9 8< 7 Vol of L(.01M)oflhe ligand in cm 8 7 6 5 4 3 2 Vol of chloroform added to 17 18 19 20 21 22 23 the ligand in cm M.FofCo+2M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance at 433 nm 0.160 0.301 0.390 0.320 0.231 0.170 0.081 123 Table(64): Continuous variation method for Cu +2 -N-phenyl-N-p- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(.01M)Cu42incm3 2 4 5 6 7. 8 Vol of pH 5 in cm 10 10 10 10 10 10 10 3 Vol of distilled .H2O in cm 13 12 11 10 9 8 7 Vol of L(.01M)ofthe ligand in cm' 8 7 6 5 4 3 2 Vol of chloroform added to 17 18 19 20 21 22 23 the ligand in cm M.FofCo+2M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance at 433 nm 0.172 0.311 0.411 0.32 0.250 0.T82 0.100 124 Table(65): Continuous variation method for Cu +2 -p-methyl-N-phenyl-p- bromobcnzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(.01M)Cu+2incm3 2 3 4 5 6 7 8 Vol of pH 5 in cm 10 10 10 10 10 10 10 3 Vol of distilled .H2O in cm 13 12 11 10 9 8 7 Vol of L(.01M)ofthe ligand in cm 8 7 6 5 4 3 2 Vol of chloroform added to 17 18 19 20 21 22 23 the ligand in cm +2 M.FofCo M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance at 433 nm 0.170 0.275 0.370 0.294 0.210 0.140 0.060 125 +2 Table(66): Continuous variation method for Cu -p-methyl-N-phenyl -o- bromobenzohydroxamic acid system. Solutions 1 2 3 4 5 6 7 Volof(.01M)Cu+2incm3 2 3 4 5 6 7 8 Vol of pH 5 in cm 10 10 10 10 10 10 10 3 Volofdistilled.H2Oincm 13 12 11 10 9 8 7 Vol of L(.01M)ofthe ligand in cm 8 7 6 5 4 3 2 Vol of chloroform added to 17 18 19 20 21 22 23 the ligand in cm M.FofCo+2M/M+L 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Absorbance at 433 nm 0.150 0.260 0.350 0.280 0.190 0.120 0.060 126 O.H-i 0.12- 6 3 0.10- I 0.08 J3 0.06- 0.04 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (16): Continuous variation plot of Cr(VI)-N-phenyl-N-o-bromobenzohydroxamic acid. 0.16- 0.14- 0.12- in s g 0.10 S < 0.06- 0.04 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (17): Continuous variation plot of Cr(VI)-N-phenyl-N-p-bromobenzohydroxamicacid. 127 0.10- s 0.08- sa J 0.06-I 0.04 0.0 0.2 . 0.4 0.6 0.8 M/(M+L) Ratio Fig (18): Continuous variation plot of Cr(VI)-p-methyl-N-phenyl-N-p-bromobenzohydroxamic acid. 0.08- a 0.07^ 0.06- o 3 0.05 A 0.04 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (19): Continuous variation plot of Cr(VI)-p-methyl-N-phenyl-N-o-bromobenzohydroxamic acid. 128 0.9- s a5 0.7- o 0.6- o ° 0.5 0.4 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (20): Continuous variation plot of Fe(III)-N-phenyl-o-bromobenzohydroxamic acid. • 0.8- B c / • \ 48 5 / * \ td 0.6- / \ o \ cd X) \ i-, \ O \ CO \ X) 0.4- <• • i * 1 * i * i < 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (21): Continuous variation plot of Fe(III)-N-phenyl-p-bromobenzohydroxamicacid. 129 0.7-, 0.6- S o.4H o x> U.3 - 0.2- 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (22): Continuous variation plot of Fe(IlI)-p-methyl-N-phenyl-p-bromobenzohydroxamic acid. 0.8- c 0.6- 0.4- o 0.2- 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (23): Continuous variation plot of Fe(Il I)-p-methyl-N-phenyl-o-bromobenzohydroxamic acid. 130 a 0.6- 1 • / \ o 0.5- / \ ts / \ 0.4- / banc e 0.3- / Absor ' 0.2- 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (24): Continuous variation plot of V(V)-N-phenyl-o-bromobenzohydroxamic acid. 0.6- o in o to 0.4- 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (25): Continuous variation plot of V(V)-N-phenyl-p-bromobenzohydroxamic acid. 131 0.6-1 0.5- o 10 a 0.4- x> O 0.3- 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (26): Continuous variation plot of V(V)-p-methyl-N-phenyl-p-bromobenzohydroxamic acid. 0.5- o 0.4- o o en 0.3- 5 0.2 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (27): Continuous variation plot of V(V)-p-methyl-N-phenyl-o-bromobenzohydroxamic acid. 132 0.06- .6a ° 0.04- g 0.02 0.00 0.0 .:; 1.0.2 0.4 o.6 0.8 . I , M/(M+L) Ratio Fig (28): Continuous variation plot of Co(II)l-N-phenyl-o-bromobenzohydroxamic acid. U.UO" • 1 0.06- / " \ 62 0 0.04- O / \ o•—* 0.02- J \ on 1 \ • 1 0.00- ' 1 ' 1 ' 1 ' 1 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (29): Continuous variation plot of Co(II)l-N-phenyl-p-bromobenzohydroxamic acid. i33 0.06-1 0.05- c 0.04H o 0.03- 0.02- O < 0.01- 0.00- 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (30): Continuous variation plot of Co(II)-p-methyl-N-phenyl-p-bromobenzohydroxamic acid. 0.06 0.05- 0.04- o 0.03- % 0.02H 0.01- 0.00 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (3 1): Continuous variation plot of Co(II)-p-methyl-N-phenyl-o-bromobenzohydroxamic acid. 134 0.4- co o -l co UJ M 0-2H u, O o.i- 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (32): Continuous variation plot of Cu(II)-N-phenyl-o-bromobenzohydroxarnic acid. 0.4- H c CO CO td 4) O 0.2- o 0.0 0.0 0.2 0.4 0.6 0.8' M/(M+L) Ratio Fig (33): Continuous variation plot of Cu(II)-N-phenyl-p-bromobenzohydroxamic acid. 135 0.4-1 0.3- rt 0.2 o o 3 0.0 -1 1 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (34): Continuous variation plot of Cu(II)-p-methyl-N-phenyl-p-bromobenzohydroxamic acid. 0.4-1 0.3- 0.2- O O to < 0.0 0.0 0.2 0.4 0.6 0.8 M/(M+L) Ratio Fig (35): Continuous variation plot of Cu(II)-p-methyl-N-phenyl-o-bromobenzohydroxamic acid. 136 3- DISCUSSION 3.1 Preparation Preparation and properties of four bromosubstituted arylhydroxamic acids were described. N-phenyl-N-p-bromobenzohydroxamic acid and N-phenyl-N-o- bromobenzohydroxamic acid were prepared by coupling of p-bromobenzoyl chloride and o-bromobenzoyl chloride with freshly prepared -P-phenyl liydroxylamine respectively. P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid and P-methyl-N- phenyl-N-o-bromobenzohydroxamic acid were prepared by coupling p- bromobenzoyl chloride and o-bromobenzoyl chloride with freshly prepared p- methyl-p-phenyl hydroxylamine respectively. The acid chlorides were prepared by re fluxing the corresponding, carboxylic acid with excess redistilled thionyl chloride to avoid acid anhydride formation, and thionyl chloride was distilled off on water bath after completion of the reaction. The coupling took place under the cold ether process which is favoured over the aqueous process due to the relative purity of products obtained. The use of sodium hydrogen carbonate in the coupling reaction is to keep the coupling medium slightly alkaline, also it serves to neutralize hydrochloric acid evolved through out the reaction. The high yield of the substituted hydroxamic acids (70-72%) can be attributed to the ortho- and para-substituents which exert steric hinderance effect that decreases the tendency to form di-derivatives. 137 All bromosubstituted hydroxamic acids prepared are white crystalline solids. They are sparingly soluble in water but readily soluble in benzene, dioxane, diethylether and chloroform. 3.2 Identification and Characterization: The acids prepared were characterized by their reactions toward acidic vanadium (V) and iron (III) solutions which give a deep-violet and blood-red colour respectively in the chloroform extract. The melting points were also determined. 3.2.1 Elemental Analysis: Elemental analysis done for the ligands prepared agreed quite well with the calculated theoretical values. 3.2.2. Infrared Spectra: Vibrational frequences of hydroxamic acids arise from the characteristic functional groups such as C = 0 , 0 - H, C - N and N - O as in Table (4)". The four hydroxamic acids prepared show several bands in the region of 4000 - 200 cm" as in appendices A,Bi C and D. The present data on hydroxamic acids has indicated that the O - H stretching of the free , unassociated hydroxyl group of the -N -OH moiety is found as a strong to weak broad band in the region 3260-3100 cm"1 The lower shift of O - H is due to the intramolecular hydrogen bonding of the type OH ... O = C ", and the lower frequencies of C = O , C -N and N - O groups of the bromosubstituted acids showed slight shift from that of the parent acid , this may be attributed to the electronic effects exerted by the substituents at ortho and para-positions. Bromosubstituents showed smaller change in I 1 7 1 I 8 ) frequenceis than chloro substituents ' , this beccause bromine has a lower electronegativity than chlorine . 138 Ortho-bromosubstituted hydroxamic acids show very broad - OH spectra this because bromine in ortho position may be engage in intramolecular hydrogen bonding with hydrogen of O -H group, this enhances -OH spectra and completely disappear. 3.2.3 Ultra - violet Spectra: Generally hydroxamic acids show , one , two or three absorption maximum bands. These bands indicate the contribution structure of hydroxamic acids which exist in two forms keto and enol A. As shown in Table (5) and appendices II,F, G and H the ultra-violet spectra of the four hydroxamic acids reveal two absorption maxima y A,max" when dissolved in chloroform , one for benzene ring and the other for the carbonyl n -n* transition. An electron withdrawing bromo-group in the ortho position bromosubstiluted displaces the higher wave length of 280 nm to 260 nm for aryl ring. 3.3. Extraction: The four hydroxamic acids prepared form coloured chelate complexes with a number of metal ions (Table 46). These acids in chloroform, react with Cr(VI) Mo (VI), Fe (III), V(V), Co (II) and Cu (II) to give golden yelloow, colourless, blood-red, reddish - violet, light- pink and green complexes respectively. The extraction of metal ions with the ligands prepared was affected with: (i) Electron withdrawing bromo-group attached to the benzene ring, (ii) Electron donating methyl-group in para position . The increase in the extraction of these metal ions when extracted with N- phenyl-N-P-bromobenzohydroxamic acid . and N-phenyl-N-o- 139 bromobenzohydroxamic acid attributed to the elecrtonegativity of the bromine atom attached to the hydroxamic acid which have a large effect on the acidity of the ligand. On the other hand introduction of methyl group causes the decrease in the extraction of metal ions this is due to +1 inductive effect of the methyl group which decreases the acidity of the ligand because the increasing of electron density on O -H axis and the proton will not be liberated freely. In general , the acidity of the hydroxamic acids may be attributed essentially to the -OH group, since stablization of the negative charge on the oxygen atom in the hydroxamate ion is possible only through induction effect . The greater the acidity of the metal chelates of o- and p-bromosubstituted hydroxamic acids are generally more stable than those of p-methyl -bromosubstituted parent compounds. (i) Chromium (VI) : Chromium (VI) was extracted in acidic medium with N-phenyl-N-p- bromobenzohydroxamic acid , N-phenyl N-o-bromobenzohydroxamic acid, P- methyl-N-phenyl-N-P-bromobenzohydroxamic acid and P-methyl -N-phenyl-N- o-bromobenzohydroxamic acid with percentage recovery of 96.00%, 97.00% ,49.00% and 98.7% atlM H,SO4 respectively ( Table 11) and 70.00%, 56.50% , 5 1.70% and 45.00% at pH 1 respectively . It is observed that the maximum extraction takes place in acidic medium and decreased sharply with the increase of pH. The pMi/2 values (Fig. 3) for Cr (VI) with N-phenyl-N-p-bromobenzohydroxamic acid ,N-pheny-N-o-bromobenzohydroxamic acid and P-methyl-N-phenyl-N-p- bromobenzohydroxamic acid are 2 , 1.9 and 1.8 respectively where the percent 40 extraction value of Cr(VI) with P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid is lower than 50%. Chromium(VI) was stripped with a high percentage recovery of 100% with 0.5M sodium hydroxide solution. (ii) Molybdenum (VI): Table (16) shows the percent extraction of Mo (VI). The maximum extraction of Mo (VI) with N-phenyl-N-p-bromobenzohydroxamic acid, N-phenyl-N-o- bromobenzohydroxamic acid, P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid and P-methyl-N-phenyl-N-o-bromobenzohydroxamic acid are 87.00% , 92.70%, 74.20% and 84.70% at pH 1 respectively. The different results recorded are due to methyl group effect at the para position which decreased the acidity of the molecule and stability of the complex. Molybdenum (VI) was almost completely extracted by aliphatic hydroxamic acids , ' ' while this percentage recovery decreased when bromosubstituted hydroxamic acids were used, such as hydroxamic acids reported in this work. Mo (VI) can be stripped completely under the medium used 0.5 M NaOH. (iii) Iron (III): 9 Fe (111) was extracted very low in acidic medium and at low pH with all hydroxamic acid prepared . Table (23) shows the percent extractions of Fe (III) with N-phenyl-N-p- bromobenzohydroxamic acid, N-phenyl-N-o-bromobenzohydroxamic acid,P- methyl-N-phenyl-N-p-bromobenzohydroxamic acid, P-methyl-N-phenyl-N-o- bromobenzohydroxamic these are 73.90% at pH 4, 71.2% at pH 4, 69.50% at pH 5 and 66.60% at pi I 4 respectively. The introduction of methyl group decreases the percentage of maximum extraction . The extractions are fully stripped under the 141 medium used (2MH?SO4) this may attributed to the weak complexing ability of Fe (III) with these acids. The pM|/9 values (Fig 8) for Fe (III) with the above four hydroxamic acids are 2,2.5,3 and 2.5 in the same respective order. (iv) Vanadium (v): Vanadium (V) extraction is very high in acidic medium or at low pH with all hydroxamic acids prepared in this work. Table (29) shows the percent extractions of V (V) with the four hydroxamic acids. The maximum extraction of vanadium (V) at pH 1 with N-phenyl-N-p- bromobenzohydroxamic acid.N-phenyl -N-o-bromobenohydroxamic acid and P- melhyl-N-phenyl-p-bromobenzohydroxamic acid and P- methyl -N-phenyl-o- bromobenzohydroxamic acid these are 93.00% 90.00, 76.00% and 88.00% respectively. Also introduction of methyl group lowers the percentage recovery. The stripping of V(V) complexes can not be achieved with 0.5 NaOH. The extractionsof vanadium (V) are not fully stripped under the medium used (0.5 Na F), the maximum stripping reaches as high as 32%. This-attributed to the high stability of the complex of VF5 which have a bridged infinite polymer. F F F ,F F ••-... F , y i\ X F F F F 142 But there is evidence from vibrational spectra for the presence of VF5 135. monomer The pH|/2 values (Fig 11) for V(V) with the above four hydroxamic acids are 5.5, 3.8, 2 mid 4.5 in the same respective order. (v) Cobalt (II): .-c^ Cobalt (II) extraction is very low at low pR'with all hydroxamic acids !; .7 prepared,;!the percent extractions increase with increase pH and precipitated at .' j high pi I. Table (35) shows the maximum percent extractions of Co (II) with N-phenyl N-p-bromobenzohydroxamic acid . N-phenyl-N-o-bromobenzohydroxamic acid, P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid and P-methyl N-phenyl-N- o-bromobenzohydroxamic acid these are 83.16% at pH 8, 54.70% at pH 7, 51.20% at pH 8 and 50.00% at pH 7 respectively. The pH1/2 values (Fig. 13) with the above four hydroxamic acids are 6.5, 6.5, 7.5 and 6.5 respectively. The extractions of Co (II) are fully stripped under the medium used (2MH2SO4). (vi) Copper (II): The percent extractions of Cu (II) are very low at low pH and increase with increase of pH and precipitated at high pH. Table (14) shows the maximum percentage extractions of Cu (II) with N- phenyl-N-p-bromobenzohydroxamic acid,-N-pheny-N-o-bromobenzohydroxamic acid,P-methyl-N-phenyl-N-p-bromobenzohydroxamic acid and P-methyl-N- phenyl-N-o-bromobenzohydroxamic acid are 93.80 at pH 6, 86.50% atpH5, 83.20% at pH 5 and 78.6% at pH 6 respectively. The pH,/2 values (Fig. 15) with the above four hydroxamic acids are 4.5, 4,4 and 3 respectively. ^ 143 The extractions of Cu (II) are fully stripped under the medium used MH2SO4 ). As reported in Tables ( 6-41) and (figures 1-15). The distribution ratios of r (VI), Mo (VI) and V(V) at pi I 1 are much greater than the distribution ratios t>f ./ . • u (II) and Co (II), therefore any one of Cr (VI), Mo (VI) and V(V) can be eparated from Cu (II) and Co (II) at pi I 1. While Cr (VI), Mo (VI) and V(V) aterfere with each other at pi I 1. The distribution ratio of Fe (III) at pi I 3 and pi I 4 are much greater than the istribution ratios of Cr (VI), Cu (II) and Co (II), therefore Fe (III) can be eparated from these metals. Fe (III) , Mo (VI) and V (V) interfere at pH 3 and annot be separated . At pi I 7 the distribution ratios of Cu (II) and Co (II) are much greater than the istribution ratios of Cr (VI) , Mo (VI), V(V) and Fe (IH)Jfherefore at the same H Cu (II) and Co (II) can be separated from any one of these metals , while Cu IF) and Co (II) can interfere at pi 1 7 and cannot be separated. From above , six metals studied can be separated from each other by Dntrolling the pi 1. These findings are expected to be useful in metallurgy studies articularly in the separation of metals. ,4. Complxes of Hydroxamic Acids: The study of the various metallic complexes with the four hydroxamic acids repared (Table 42-47) has revealed the fact that the hydroxamic acids usually act sa bidenlate ligands. The reactions of Cr (VI), Mo (VI) Fe (III), V (V), Cu (II) and Co (II) with all lese hydroxamic acids give complexes formed by different molar ratios of gands and metal ions at optimum pll. This stiochiometric ratio confirmed by lemental analysis and molecular weight determination. H-1 Cr (V) ;at 1M \H2SO4 have been found to give a composition of I Cr: 2 acid? ilrile Mo (VI) gives the same ratio at pllI. Iron (III) forms complexes of 1:1 metal /ligand ratio at pi I 4 and 5. Some ;|presentalive doubly bridged complexes of iron (III) are shown and these with a i , ,. ,- r, ,- 1.56-137 ear or nearly linear re-Ore /N /N \ 7,e \ / Ff ! O -' • O •• • . O \N \ N Vanadium (V) complexes are of the same trend as iron (III) complexes at pHl. hi (II) and Co (II) from complexes of 1 : 2 melal/ligand ratio at pH (6,7 and 8). 1.5. Continuous Variation Method: This method is rapid ami simple for determining the formula of a jompound (Table 48-66) and figures (16-35). The ligand forms I : 2 complexes s/ith Cr (VI), Cu (II) and Co (II), and forms 1 : 1 complexes with Fe (III) and This work can be further investigated by X-ray and mass spectra to support }he conclusions reported. 145 c VD 3 Aooendu {S} /V A;r • • r WOO ISCC 7C0O 2500 2CC0 !SCO •;5oo 1400 1200 1C0O 300 6CO 400 — N~phenyl - H-0 -bromobenzohyd - roxomic acid 1800 1500 1400 1200 rax 3C0 600 £02 S500 3000- 2500 2000 1 WAVE NUMBER (CM" ) : acid CO 2 2 o II a .a 200 240 2S0 3 20 360 400 440 480 520 560 (500 150 L- -. ...... — — — _- — — i .... _ ...... 1 Ap (end ix (F —_ —,— . — — - •- • i—i •'••-• :/ 1 — ••- 1 - • — —. i V -- - —• : —»—-—-_ — — 200 ; 280 3 2O'~36"d"4OO"446"48O 520 560 600 151 200 240 280 3 20 360 400 440 4R0. 520 560 600 _-_ ill : - - i ! i — .. _. ——~ ...... ...... Ap !ix( ...... •!)'.':. — "r .i i- <*- r - -••- L eO — — / ..... — —. — : \ — — - - •JI ii »i— TTV - ... '[••• i: —:--.-- .. .. 153 PREFERENCES 1. 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