DOCSLIB.ORG

Reevaluation of Donor Number Using Titration Calorimetry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Reevaluation of Donor Number Using Titration Calorimetry ANALYTICAL SCIENCES FEBRUARY 2012, VOL. 28 103 2012 © The Japan Society for Analytical Chemistry Reevaluation of Donor Number Using Titration Calorimetry Misaki KATAYAMA,* Mitsushi SHINODA,** Kazuhiko OZUTSUMI,* Shigenobu FUNAHASHI,** and Yasuhiro INADA*† * Department of Applied Chemistry, College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525–8577, Japan ** Laboratory of Analytical Chemistry, Department of Chemistry, Faculty of Science, Nagoya University, Chikusa, Nagoya 464–8602, Japan Many empirical parameters have been suggested to measure solvent effects in chemical reactions. Gutmann’s donor number has been a successful parameter to quantify the electron-donating property of the solvent molecule; it is defined as the enthalpy change of the addition reaction of solvent molecule to SbCl5 in 1,2-dichloroethane. Calorimetric measurements can be applied to determine the quantity. Because the existence of water is critical for reactions in organic solvents, we have analyzed the enthalpy change using the titration calorimetry while considering the complexation with water. The determined donor numbers of formamide, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and 1,1,3,3-tetramethylurea (TMU) are 22.4, 26.5, 30.0, and 40.4, respectively. The values of DMF and DMSO are in perfect agreement with those of Gutmann. A reliable value for TMU is obtained for the first time on the basis of the enthalpy change for the addition reaction. (Received August 8, 2011; Accepted November 4, 2011; Published February 10, 2012) molecules. Introduction The electron-donating property of solvent is important to interpret the stability and reactivity of metal species in solution. Non-aqueous solvents are useful for many chemical reactions Gutmann has defined it as the absolute value of the enthalpy which do not easily proceed in water. The thermodynamic change for the 1:1 complex formation reaction of the donor properties of a chemical reaction in solution largely depend on molecule with SbCl5 in 1,2-dichloroethane. The SbCl5 molecule the physicochemical properties of the solvent. Many empirical was selected as the standard acceptor molecule because of its parameters have been suggested to compare the solvent effect in strong accepting property for the electron pair of the donor 1 2 3 chemical reactions, such as Kosower’s Z, Dimroth’s ET, Y, molecule. The SbCl5 molecule has only one accepting site and 4 and Ω. The Z and ET values are parameterized using the therefore it forms only the 1:1 complex with the donor molecule charge-transfer absorption band of the probe molecule, with (L), as shown in Eq. (1): which the solvent molecule forms an adduct, in the solvent. The Y value is defined using the rate constant of the solvolysis SbCl5 + L SbCl5L (1) reaction of t-butyl chloride. The Ω value is obtained from the ratio of the endo-product to the exo-product of the Diels–Alder The molecular geometry changes from trigonal bipyramidal to reaction. The solubility parameter δ, which is defined by the distorted octahedral structure in the complexation reaction, and molar energy of evaporation and the molar volume of solvent, the reaction is not accompanied by dissociation of the chloride is also important to understand the solvent effect.4 These ion. The formal charge is kept neutral for the reactions with the parameters mainly represent the properties of solvents as the neutral L, and the electrostatic contribution from the solvation electron acceptor, and it is known that they correlate with change is thus almost negligible to the enthalpy change. Mayer’s acceptor number (AN).5 The AN value is defined as Gutmann has experimentally determined the enthalpy change by the relative chemical shift of 31P NMR of trimethylphosphine means of calorimetry and has reported the DN values for many oxide in a solvent, and is widely used as a measure of the donor molecules that are usually used as solvents.7 Gutmann’s accepting property of the solvent molecule when combined with DN is now widely accepted as a good measure of the donating the Gutmann’s donor number (DN),6,7 which is a measure of the property of solvents, and the values help researchers to donating property. The β and α values of Kamlet–Taft are also understand the solvation structure and the solvation equilibrium proposed as the parameters to measure the solvent-solute of metal ions. The application of these parameters is expanding interaction, which is related to the donating property.8–10 from the basic solution chemistry into applied materials However, these parameters mainly represent the chemistry, such as the estimation of surface functionality of hydrogen-bonding interaction between the solvent and solute mesoporous silica.11 As the importance of the DN increases, a systematic † To whom correspondence should be addressed. knowledge of a variety of solvents becomes necessary to E-mail: [email protected] compare quantitatively the solvent nature. Erlich and Popov 104 ANALYTICAL SCIENCES FEBRUARY 2012, VOL. 28 estimated the value of DN using the linear relationship between solution into the cell. The titrant solution passed through the 23 the chemical shift of Na NMR of the NaClO4 solution and the heat exchanger to maintain constant temperature of the solution known value of DN.12 This approach, however, is based on a and was then introduced into the reaction cell. A DC current hypothesis that the solvation structure of the Na+ ion is the same generator (R6142, Advantest) was used to supply a specified in each solvent. There is a similar attempt using the chemical current to the heater in order to calibrate the potential difference 1 13 shift of H NMR of CHCl3 in the solvent. In this case, the to the generated heat. dipolar interaction between the solvent molecules and CHCl3 is Measurements of the reaction heat were performed by titrating emphasized rather than the electron-donating property. the 1,2-dichloroethane solution of each donor solvent into the Formamide (FA) and 1,1,3,3-tetramethylurea (TMU) are good 1,2-dichloroethane solution of SbCl5. The initial concentration solvents for electrolytes, and their DN values of 24 and 31 were and volume of titrand (SbCl5 solution) were around 1.0 × reported by Popov et al., respectively.12 The chemical behavior 10–3 mol dm–3 and 60.0 cm3, respectively, and the total volumes in FA is often compared with that in the other amides, such as of the added titrant solution were 11.0 cm3 for DMF, 13.0 cm3 N-methylformamide and N,N-dimethylformamide (DMF). for DMSO, 17.0 cm3 for TMU, and 13.0 cm3 for FA with the Although the DN value of FA (24) is slightly smaller than that concentration of around 2.0 × 10–2 mol dm–3. of DMF (26.6), such a comparison must be carefully done because the value of FA is estimated by a different method from Data analysis that used for DMF.6,7,12 Similarly to the case of FA, although the The heat, q(t), generated per unit time in the solution of the chemical characteristics of metal ions in TMU such as the volume, V, is expressed by Eq. (2), solvation structure are compared with those in the other amides on the basis of DN values,14–16 it should be noted that they are dθ()t ()CVp +Ccell = q() t − λθ()t (2) not determined by the same experimental method. It has been dt reported that the solvation number of the metal ion is variable from 4 to 6 according to the ionic size and charge in TMU with where Cp is the volumetric heat capacity of the sample solution, 14–20 the bulky molecular structure. In order to interpret the Ccell the heat capacity of the blank vessel, θ(t) the temperature of bulkiness effect of TMU on the solvation structure of metal the solution at time t, and λ the heat-transfer coefficient between ions, the donating property of solvent molecules must be the vessel and the atmosphere. The potential difference, e(t), of quantitatively compared with those of other solvents. It is thus the thermistor sensor dipped in the titrated solution is related to important and necessary to reevaluate the DN values of FA and θ(t) by Eq. (3) with a proportional factor, A. TMU based on the original definition. In the present study, we have carried out a reevaluation of the e(t) = Aθ(t) (3) DN values for the donor ligand of FA, DMF, and TMU using titration calorimetry to determine precisely the reaction heat of After finishing generation of the reaction heat, θ(t) follows Eq. (1). Because the water molecule existing in 1,2-dichloroethane Newton’s law of cooling. Thus, the e(t) value is expressed by solution easily binds to SbCl5 and greatly affects the observed Eq. (4) in the time region of t ≥ ts, values of enthalpy change, the dissociation of water has been taken into consideration in analyzing the titration data. The λ e() t =e() ts exp − (t− ts ) (4) corresponding value of dimethyl sulfoxide (DMSO) has also CVp +Ccell been reevaluated in this study to estimate the validity of our procedures of data analysis, because the DN value of DMSO where ts is the time at which the generation of the heat was was also determined by Gutmann using calorimetry. The values entirely completed. In this study, ts was set as the time when the determined in this study will be compared with those reported e(t) value became 60% of its maximum. Then, the generated previously. gross heat, Q, is given by Eq. (5): λ ts 1 Q =e() t dt + e() ts()CV p +Ccell (5) Experimental A ∫0 A Sample solutions Determination of the Q value was performed in the following Reagent grade 1,2-dichloroethane (Nakarai), N,N-dimethyl- manner.
Load more

Recommended publications
  • Oxygen Reduction Reactions in Ionic Liquids and the Formulation of a General ORR Mechanism for Li−Air Batteries † † † † ‡ Chris J
    Article pubs.acs.org/JPCC Oxygen Reduction Reactions in Ionic Liquids and the Formulation of a General ORR Mechanism for Li−Air Batteries † † † † ‡ Chris J. Allen, Jaehee Hwang, Roger Kautz, Sanjeev Mukerjee, Edward J. Plichta, ‡ † Mary A. Hendrickson, and K. M. Abraham*, † Department of Chemistry and Chemical Biology, Northeastern University Center for Renewable Energy Technology (NUCRET), Northeastern University, Boston, Massachusetts 02115, United States ‡ Power Division, U.S. Army RDECOM CERDEC CP&I, RDER-CCP, 5100 Magazine Road, Aberdeen Proving Ground, Maryland 21005, United States ABSTRACT: Oxygen reduction and evolution reactions (ORRs and OERs) have been studied in ionic liquids containing singly charged cations having a range of ionic radii, or charge densities. Specifically, ORR and OER mechanisms were studied using cyclic and rotating disk electrode voltammetry in the neat ionic liquids (ILs), 1-ethyl- 3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) and 1-methyl-1-butyl-pyrrolidinium bis- fl (tri ouromethanesulfonyl)imide (PYR14TFSI), and in their solutions containing LiTFSI, NaPF6, KPF6, and tetrabutylam- fl monium hexa uorophosphate (TBAPF6). A strong correlation was found between the ORR products and the ionic charge density, including those of the ionic liquids. The observed trend is explained in terms of the Lewis acidity of the cation present in the electrolyte using an acidity scale created from 13C − 13 NMR chemical shifts and spin lattice relaxation (T1) times of C O in solutions of these charged ions in propylene carbonate (PC). The ionic liquids lie in a continuum of a cascading Lewis acidity scale with respect to the charge density of alkali metal, IL, and TBA cations with the result that the ORR products in ionic liquids and in organic electrolytes containing any conducting cations can be predicted on the basis of a general theory based on the hard soft acid base (HSAB) concept.
    [Show full text]
  • 2701X0073.Pdf
    COORDINATION AND REDOX PROPERTIES IN SOLUTION YIKTOR GUTMANN Inst it Ut für Anorganische Chemie der Technischen Hochschule Wien, Austria ABSTRACT A primitive description of the functional electron cloud is given and is used to account for the mutual influence between coordinating and redox properties. Rules are given for the change in redox properties by coordination and vice versa. It is further shown that the redox potential in a donor solvent is determined by its donor number and an empirical approach is suggested to obtain the electromotive series for any solvent of given donor number. The donor number is also considered important for the ionization of a covalent substrate. Finally a new classification is suggested for charge-transfer complexes. THE PRIMITIVE DESCRIPTION OF THE FUNCTIONAL ELECTRON CLOUD In a primitive way, a characteristic 'electron cloud' may be ascribed to each atom, ion or molecule. Even in the state of highest stability of the entity, the ground state, the electronic arrangement is usually far from 'ideal' as is evidenced by the tendency to undergo chemical reactions. In the primitive description of the 'functional electron cloud', the 'non-ideality' of the cloud is considered responsible for its tendency to change; the actual function will depend also on the properties of the reactant. The functional cloud may deviate from the ideal by being either too 'dilute' or too 'dense' compared with that of the reacting molecule. An entity with a 'dilute' electron cloud will tend to gain electrons or to achieve an appropriate share of them and will thus function as an acceptor of elec- trons.
    [Show full text]
  • Ionic Equilibria in Donor Solvents
    IONIC EQUILIBRIA IN DONOR SOLVENTS U. MAYER Technical University of Vienna, Department of Inorganic Chemistry, A-1060 Vienna, Austria ABSTRACT It is shown that coordination chemical and extrathermodynamic models may be successfully applied to the qualitative and also quantitative description of fundamental chemical equilibria and reaction rates in non-aqueous solvents. Applications include: formation of charge transfer complexes, electrochemical reduction of metal cations, ionization of covalent compounds, ion association phenomena, outer sphere interactions and the kinetics of substitution reactions. I. INTRODUCTION During recent decades rapid developments have taken place in the field of non-aqueous solution chemistry. This may be attributed to: first, the increased use of non-aqueous solvents as reaction media in preparative chemistry and in technological processes; and second, the ever-increasing importance of these solvents within the scope of physical chemical studies on the nature of solute—solvent interactions. The previous lack of efficient models for a generalized description of solute—solvent interactions was undoubtedly due to the fact that physical chemists concentrated their efforts for many years on aqueous solutions or at best on a few closely related solvent systems. Thus, only when scientists began to study suitable model reactions in a variety of non-aqueous media with widely different properties has it become possible to establish generalized relationships between chemical reactivity and solvent properties, to test critically existing theories, and to develop new and more efficient models. The main problem in solution chemistry is the characterization of ion— solvent interactions. It is well known that single ion solvation quantities cannot be determined by purely thermodynamic methods.
    [Show full text]
  • Consideration of Hansen Solubility Parameters. Part 3 Donor/Acceptor Interaction
    Hansen Solubility Parameters 50th anniversary conference, preprint 2017 PP. 22-36(2017) Consideration of Hansen Solubility Parameters. Part 3 Donor/Acceptor interaction HSPiP Team: Hiroshi Yamamoto, Steven Abbott, Charles M. Hansen Abstract： Dr. Hansen divided the energy of vaporization into a dispersion term (δD), a polar term (δP) and a hydrogen bond term (δH) in 1967. These set of parameters are called Hansen Solubility Parameters (HSP). We treat HSP as a three-dimensional vector. When these HSP are applied to, for example, pigment dispersion for paints, problems have been pointed out such as the inability to evaluate the difference in dispersibility between acidic and basic pigments. Many attempts have been made to divide this hydrogen bond term into Donor (Acid) and Acceptor (Base). But when we were building HSP distance equation, we could not correctly evaluate the donor/acceptor interaction. In this paper, we used Gutmann's Donor Number (DN), Acceptor Number (AN) obtained from the solvation energy of mixing via spectroscopic analysis of mixing the solvent with a probe solute. The donor/acceptor property of the whole molecule obtained here is allocated to the functional groups constituting the molecule, and an expression that can easily calculate the donor and acceptor of the molecule was developed. By introducing this donor/acceptor, a deeper analysis of solubility in water, liquid-liquid extraction, dispersibility of pigment, vapor-liquid equilibrium become possible. Key Words: Hansen Solubility Parameter, Donor, Acceptor 1. Introduction: Brønsted-Lowry Acid/Base: 1.1. The Solubility Parameter and Acid/Base Brønsted and Lowry defined the acid as "able to emit H+" and the base as "able to receive H+".
    [Show full text]
  • Itll Lawrence Berkeley Laboratory Iii:~ UNIVERSITY of CALIFORNIA APPLIED SCIENCE
    LBL-24543 C'_~ ITll Lawrence Berkeley Laboratory iii:~ UNIVERSITY OF CALIFORNIA APPLIED SCIENCE -. ~ ., .. I DIVISION. •-, l:: '-' 1:: v L _ LAWRENCE EJr.:ov~L''"V_, .nc: c' LABORATORY APR 1 9 1988 LIBRARY AND The Use of Basic Polymer Sorbents DOCUMENTS SECTION for the Recovery of Acetic Acid from Dilute Aqueous Solution A.A. Garcia and C.J. King January 1988 '· . J I • .I APPLIED SCIENCE DIVISION Prepared for the U.S. Department of Energy under Contract DE-AC03-76SF00098 DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of Califomia. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California. LBL-24543 The Use of Basic Polymer Sorbents For The Recovery of Acetic Acid From Dilute Aqueous Solution Antonio Agustin Garcia and C.
    [Show full text]
  • Donor Number of Mixed Meoh Solvents Using a Solvatochromic Cu(II)-Complex
    Journal of the Korean Chemical Society Vol. 36, No. 6, 1992 Printed in the Republic of Korea 분광용매화 구리 (U) 착물에 의한 메탄을 이성분 혼합용매들의 Donor Number 柳承敎•金鎮成•司空烈* 한양대학교 자연과학대학 화학과 (1992. 6. 4 접수 ) Donor Number of Mixed MeOH Solvents Using a Solvatochromic Cu(II)-Complex Seoung-Kyo Yoo, Jin Sung Kim, and Yeol Sakong* Department of Chemistry, Hanyang University, Seoul 133-791, Korea (Received June 4, 1992) 유 약 . 분광용매화 기질인 [Cu(tmen)(acac)]ClC)4를 이용하여 혼합용매의 Lewis basicity윽 1 Gutmann의 Donor Number(DN)를 측정하였다 . 측정된 여덟가지 MeOH 혼합용매들 의 DN값 변화는 단순히 용매의 조성변화와 일치하지 않을 뿐만 아니라 혼합웅매들 은 그 변화 형태에 따라 세 개의 그룹으로 구분할 수가 있었다 . (1) 기질에 대한 용매화가 주로 cosolvent들에 의해 이루어지는 경우 ＜MeOH-DMSO, MeOH-PY, MeOH・DMF)와 (2) 기질 의 용매화에 혼합용매의 두 성분 이 거의 동일하게 영향을 미치는 경우 (MeOH-MeCN, MeOH-dioxanet MeOH-AC) 및 (3) 전적으로 MeOH에 의한 기질의 용매화가 이루어지는 경우이다 (MeOH-DCE, MeOH-TCE). 또한 순수한 용매들의 경우와 마찬가지로 이들 혼합용매들에 대한 DN과 Kam- 의 basicity 변수인 BKT 값들간에는 비교적 좋은 상관관계성을 볼 수 있었으며 , 흔합용매들의 반응성 해석에서도 유용한 인자로 사용될 수 있음을 알았다 . ABSTRACT. An emprical Lewis basicity, DN, for eight mixed methanol solvents has been measured by the solvatochromic behaviour of the [ Cu(tmen)(acac)J C104. The change of DN in mixed methanol solvents is not correlated with composition of the mixtures and divided into three groups: (1) dipolar aprotic solvents contribute mainly to the solvation of s이나 e (MeOH-DMSOt MeOH-PY, MeOH-DMF), (2) two components of mixture contribute equally to the solvation of solute (MeOH-MeCN, MeOH-dio- xanef MeOH-AC) and (3) methanol contributes entirely to the solvation of solute (MeOH-DCE, MeOH- TCE).
    [Show full text]
  • Unraveling the Correlation Between Solvent Properties and Sulfur Redox Behavior in Lithium-Sulfur Batteries Qi He,1,Z Yelena Gorlin, 1,A,∗ Manu U
    Journal of The Electrochemical Society, 165 (16) A4027-A4033 (2018) A4027 Unraveling the Correlation between Solvent Properties and Sulfur Redox Behavior in Lithium-Sulfur Batteries Qi He,1,z Yelena Gorlin, 1,a,∗ Manu U. M. Patel,1 Hubert A. Gasteiger,1,∗∗ and Yi-Chun Lu 2,∗,z 1Chair of Technical Electrochemistry, Department of Chemistry and Catalysis Research Center, Technical University of Munich, Munich, Germany 2Electrochemical Energy and Interfaces Laboratory, Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Hong Kong Systematic understanding of how solvent property influences Li-S redox chemistry is required to develop an effective electrolyte for Li-S batteries. In this study, we investigate the correlation between solvent property and Li-S redox chemistry in nine non-aqueous electrolyte solvents that cover a wide range of three main solvent physiochemical properties, namely dielectric constant (ε), Gutmann donor number (DN), and acceptor number (AN). We exploit various analytical techniques including cyclic voltammetry, rotating ring disk electrode technique, UV-Vis spectroscopy and galvanostatic measurement in a two-compartment cell. We show that the potential of S8-reduction increases with increasing AN and that the polysulfide-reduction/oxidation is strongly influenced by the DN. The common discrepancy in the literature on the role of dielectric constant and donor number is addressed by examining the redox reactions, polysulfide stability, and the effect of salt concentration in acetonitrile - a solvent with high dielectric constant and low DN. We show that the DN is the primary descriptor for polysulfide redox reactions, as it controls the effective charge density of the solvated cation (Li+), which affects the stability of polysulfides with different charge density via Pearson’s Hard Soft Acid Base theory.
    [Show full text]
  • Acid Dissociation Constant - Wikipedia, the Free Encyclopedia Page 1
    Acid dissociation constant - Wikipedia, the free encyclopedia Page 1 Help us provide free content to the world by donating today ! Acid dissociation constant From Wikipedia, the free encyclopedia An acid dissociation constant (aka acidity constant, acid-ionization constant) is an equilibrium constant for the dissociation of an acid. It is denoted by Ka. For an equilibrium between a generic acid, HA, and − its conjugate base, A , The weak acid acetic acid donates a proton to water in an equilibrium reaction to give the acetate ion and − + HA A + H the hydronium ion. Key: Hydrogen is white, oxygen is red, carbon is gray. Lines are chemical bonds. K is defined, subject to certain conditions, as a where [HA], [A−] and [H+] are equilibrium concentrations of the reactants. The term acid dissociation constant is also used for pKa, which is equal to −log 10 Ka. The term pKb is used in relation to bases, though pKb has faded from modern use due to the easy relationship available between the strength of an acid and the strength of its conjugate base. Though discussions of this topic typically assume water as the solvent, particularly at introductory levels, the Brønsted–Lowry acid-base theory is versatile enough that acidic behavior can now be characterized even in non-aqueous solutions. The value of pK indicates the strength of an acid: the larger the value the weaker the acid. In aqueous a solution, simple acids are partially dissociated to an appreciable extent in in the pH range pK ± 2. The a actual extent of the dissociation can be calculated if the acid concentration and pH are known.
    [Show full text]
  • New Conceptual Understanding of Lewis Acidity, Coordinate Covalent Bonding, and Catalysis Joshua A
    Duquesne University Duquesne Scholarship Collection Electronic Theses and Dissertations Summer 2009 New Conceptual Understanding of Lewis Acidity, Coordinate Covalent Bonding, and Catalysis Joshua A. Plumley Follow this and additional works at: https://dsc.duq.edu/etd Recommended Citation Plumley, J. (2009). New Conceptual Understanding of Lewis Acidity, Coordinate Covalent Bonding, and Catalysis (Doctoral dissertation, Duquesne University). Retrieved from https://dsc.duq.edu/etd/1052 This Immediate Access is brought to you for free and open access by Duquesne Scholarship Collection. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of Duquesne Scholarship Collection. For more information, please contact [email protected]. NEW CONCEPTUAL UNDERSTANDING OF LEWIS ACIDITY, COORDINATE COVALENT BONDING, AND CATALYSIS A Dissertation Submitted to the Bayer School of Natural and Environmental Sciences Duquesne University In partial fulfillment of the requirements for the degree of Doctor of Philosophy By Joshua A. Plumley August 2009 NEW CONCEPTUAL UNDERSTANDING OF LEWIS ACIDITY, COORDINATE COVALENT BONDING, AND CATALYSIS By Joshua A. Plumley Approved August 2009 __________________________________ __________________________________ Jeffrey D. Evanseck Ellen Gawalt Professor of Chemistry and Biochemistry Assistant Professor of Chemistry and Dissertation Director Biochemistry Committee Member Committee Member __________________________________ __________________________________ Douglas J. Fox
    [Show full text]
  • Chemical Properties of Water-Miscible Solvents Separated by Salting-Out and Their Application to Solvent Extraction
    ANALYTICAL SCIENCES JUNE 1994, VOL. 10 383 Chemical Properties of Water-Miscible Solvents Separated by Salting-out and Their Application to Solvent Extraction Masaaki TABATAt, Midori KUMAMOTO and Jun NISHIM0T0 Department of Chemistry, Faculty of Science and Engineering, Saga University, Honjo-machi, Saga 840, Japan Fourteen water-miscible polar solvents were investigated for the separation from their aqueous solutions by salting-out using sodium chloride (4 mol dm-3). The following solvents showed the phase separation: acetone , acetonitrile, 1,4- dioxane, tetrahydrofuran, l-propanol, and 2-propanol. The chemical properties of the separated organic solvents were determined by measuring ET(30) (1.196X105/2 (kJ mol-')) and D11,1(=1.196X105 ()i'1) (kJ mol-')) values from the spectral change of 2,6-Biphenyl-4-(2,4,6-triphenylpyridinio)phenolate (DTP) and bis(1,3-propanediolato)vanadium(IV) (VO(acac)2), where 2, A,, and 2„ denote the absorption maximum wavelengths (nm) of DTP and VO(acac)2. Solvent properties of acetone, acetonitrile, 1,4-dioxane, and tetrahydrofuran were dramatically altered by the salting- out. Acceptability of the phase-separated solvents increased due to the dissolution of water molecules having large acceptor numbers. The ion-pair complex of tris(1,10-phenanthroline)iron(II) chloride was easily extracted into the phase-separated acetonitrile by the salting-out. Some metal chelates of 1-(2-pyridylazo)-2-naphthol (Hpan) and 8-quinolinol (Hox), 5,10,15,20-tetraphenylporphyrin (H2tpp), and ionic species (H2ox+, ox, and H4tpp2+) were also extracted into 1,4-dioxane. The raised donor and acceptor abilities of the phase-separated solvents allowed application to solvent extraction.
    [Show full text]
  • Bronsted-Lowry
    CH4. Acids and Bases 1 Bronsted-Lowry Bronsted-Lowry definitions: Acid = proton donor; Base = proton acceptor + - HF (aq) + H2O H3O (aq) + F (aq) BL acid BL base Fluoride ion is the conjugate base of HF Hydronium ion is the conjugate acid of H2O 2 1 Amphiprotic species Amphiprotic – species that can act as BL acid or base + NH3 (aq) + H2O NH4 (aqu) + OH (aqu) BL base BL acid hydroxide + Kb = base dissociation constant = [NH4 ] [OH ] / [NH3] H2O is amphiprotic - it‟s a base with HF, but an acid with NH3 3 BL acid/base strength Ka, the acidity constant, measures acid strength as: + - Ka = [H3O ] [A ] / [HA] pKa = - log Ka For strong acids - When pH = pKa, then [HA] = [A ] pKa < 0 pKa(HCl) ≈ -7 4 2 BL acid/base strengths 5 Kw Kw = water autodissociation (autoionization) constant + - 2 H2O H3O (aqu) + OH (aqu) + - -14 Kw = [H3O ] [OH ] = 1 x 10 (at 25°C) Using the above, you should prove that for any conjugate acid-base pair: pKa + pKb = pKw = 14 6 3 Polyprotic acids Since pKa values are generally well- separated, only 1 or 2 species will be present at significant concentration at any pH - + H3PO4 + H2O H2PO4 + H3O pKa1 = 2.1 - 2- + H2PO4 + H2O HPO4 + H3O pKa1 = 7.4 2- 3- + HPO4 + H2O PO4 + H3O pKa1 = 12.7 7 Solvent leveling + The strongest acid possible in aqueous solution is H3O + - Ex: HCl + H2O H3O (aq) + Cl (aq) there is no appreciable equilibrium, this reaction goes quantitatively; the acid form of HCl does not exist in aqueous solution + - Ex: KNH2 + H2O K (aq) + OH (aq) + NH3 (aq) this is solvent leveling, the stable acid and base species are the BL acid-base pair of the solvent - NH2 = imide anion - NR2 , some substituted imide ions are less basic and can exist in aq soln 8 4 Solvent leveling Only species with 0 < pKa < 14 can exist in aqueous solutions.
    [Show full text]
  • Determination of Pka Values of Some Sulfonamides by LC and LC-PDA Methods in Acetonitrile-Water Binary Mixtures
    J. Braz. Chem. Soc., Vol. 21, No. 10, 1952-1960, 2010. Printed in Brazil - ©2010 Sociedade Brasileira de Química 0103 - 5053 $6.00+0.00 Determination of pKa Values of Some Sulfonamides by LC and LC-PDA Methods in Acetonitrile-Water Binary Mixtures Article Nurullah Şanli,*,a Senem Şanli,a Güleren Özkanb and Adil Denizlic aDepartment of Chemistry, Faculty of Science and Arts, Hitit University, 19040, Çorum, Turkey bDepartment of Chemistry, Faculty of Science and Arts, Süleyman Demirel University, 32100, Isparta, Turkey cDepartment of Chemistry, Faculty of Science, Hacettepe University, 06800, Beytepe, Ankara, Turkey As constantes de dissociação de sete sulfonamidas antibióticas, sulfadiazina, sulfatiazol, sulfamerazina, sulfametazina, sulfamonometoxina, sulfadoxina e sulfametoxazol, foram determinadas em diferentes misturas binárias acetonitrila-água (15, 30, 40, 50% (v/v)) usando cromatografia líquida de fase reversa. Um método usando espectros de absorbância no máximo dos picos cromatográficos previamente obtidos foi também aplicado para determinar os valores de pKa. Este método pode ser aplicado a dados oriundos de equipamentos LC-UV (com detecção por arranjo de diodos, PAD) retendo todas as vantagens dos métodos LC e espectrofotométricos. Correlações lineares foram observadas quando os valores calculados de pKa das sulfonamidas em diferentes misturas de solventes foram comparados com a fração molar da acetonitrila. The dissociation constants of seven sulfonamide antibiotics, sulfadiazine, sulfathiazole, sulfamerazine, sulfamethazine, sulfamonomethoxine, sulfadoxine and sulfamethoxazole, have been determined in different acetonitrile-water binary mixtures (15, 30, 40, 50% v/v) by means of reversed-phase liquid chromatographic data. Also, a method based on the absorbance spectra at the maximum of chromatographic peaks previously obtained has been applied to determine the pKa values.
    [Show full text]