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Organic Chemistry –II
Subject Chemistry Paper No and Title Paper 5: Organic Chemistry –II Module No and Title Module 5: Methods of determining mechanisms and Isotope effects Module Tag CHE_P5_M5_e-Text CHEMISTRY PAPER No. 5: Organic Chemistry -II MODULE No. 5: Methods of determining mechanisms and Isotope effects TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. Methods of determining mechanism 3.1 Determination of the products formed 3.2 Study of Intermediate formed 3.3 Study of catalyst 3.4 Stereochemical Evidence 3.5 Kinetic evidence 3.6 Isotope Labelling 4. Isotopic Effects 5. Summary CHEMISTRY PAPER No. 5: Organic Chemistry -II MODULE No. 5: Methods of determining mechanisms and Isotope effects 1. Learning Outcomes After studying this module, you shall be able to • Know what do we mean by mechanism of a reaction • Learn the ways to determine mechanism of a reaction • Identify the reactants, products and intermediates involved in a reaction • Evaluate the steps involved in a reaction 2. Introduction In scientific experiments and chemical reactions, all we can do is try to account for the observations by proposing theories and mechanisms. Reaction mechanisms have been an integral part of the teaching of organic chemistry and in the planning of routes for organic syntheses for about 50 years. The first sentence of Hammett’s influential book, Physical Organic Chemistry, states, “A major part of the job of the chemist is the prediction and control of the course of chemical reactions” In a chemical reaction, mechanism depicts the actual process by which the reaction has taken place. It indicates which bonds are broken, in what order, the steps involved and the relative rate of each step. -
Chemistry Inventory; Fall
CHEMISTRY FALL 2005 MSDS Mfg.'s Name Chemical Name Quantity Stored Storage Conditions (on file = 9) Aluminum 9 1.5 kg Aluminum chloride, anhydrous, 98.5% 9 0.2 kg Aluminum chloride · 6H2O 9 0.5 kg Aluminum hydroxide 9 0.5 kg Aluminum nitrate 9 0.5 kg Aluminum sulfate 9 0.5 kg Ammonia, concentrated 9 4.0 L Ammonium acetate 9 0.2 kg Ammonium chloride 9 Ammonium dihydrogen phosphate (monobasic) 9 0.4 kg J.T. Baker Ammonium hydrogen phosphate (dibasic) No 0.5 kg Ammonium nitrate 9 2.5 kg Ammonium oxalate 9 0.7 kg Ammonium peroxydisulfate 9 0.5 kg Ammonium sulfate 9 0.2 kg Antimony 9 0.4 kg Barium chloride, anhydrous 9 2.5 kg Barium chloride · 2H2O 9 2.5 kg Barium nitrate 9 0.8 kg Bismuth 9 2.0 kg Boric Acid 9 0.4 kg Brass 9 Bromine 9 2.5 kg Cadmium 9 0.1 kg Cadmium nitrate 9 0.3 kg Calcium acetate · xH2O 9 0.5 kg Calcium carbide 9 1.0 kg Calcium carbonate 9 2.2 kg Calcium chloride 9 1.0 kg Calcium hydroxide 9 0.3 kg Calcium nitrate · 4H2O 9 1.0 kg Calcium oxide 9 0.3 kg Calcium sulfate · 2H2O 9 1.0 kg Carbon 9 0.1 kg Ceric ammonium nitrate 9 0.5 kg Cesium chloride 9 0.01 kg Chromium 9 0.01 kg Chromium chloride 9 0.5 kg Chromium nitrate 9 0.5 kg Cobalt 9 0.025 kg Cobalt chloride 9 0.7 kg Cobalt nitrate 9 0.6 kg Copper (assorted) 9 4.0 kg Copper acetate 9 0.05 kg Copper chloride 9 0.1 kg Copper nitrate 9 3.5 kg Copper oxide 9 0.4 kg Cupric sulfate, anhydrous 9 0.5 kg Cupric sulfate · 5H2O 9 2.75 kg EDTA 9 0.6 kg Iodine 9 2.0 kg Iron (assorted) 9 5.0 kg MSDS Mfg.'s Name Chemical Name Quantity Stored Storage Conditions (on file = 9) Ferric ammonium -
Step-By-Step Guide to Better Laboratory Management Practices
Step-by-Step Guide to Better Laboratory Management Practices Prepared by The Washington State Department of Ecology Hazardous Waste and Toxics Reduction Program Publication No. 97- 431 Revised January 2003 Printed on recycled paper For additional copies of this document, contact: Department of Ecology Publications Distribution Center PO Box 47600 Olympia, WA 98504-7600 (360) 407-7472 or 1 (800) 633-7585 or contact your regional office: Department of Ecology’s Regional Offices (425) 649-7000 (509) 575-2490 (509) 329-3400 (360) 407-6300 The Department of Ecology is an equal opportunity agency and does not discriminate on the basis of race, creed, color, disability, age, religion, national origin, sex, marital status, disabled veteran’s status, Vietnam Era veteran’s status or sexual orientation. If you have special accommodation needs, or require this document in an alternate format, contact the Hazardous Waste and Toxics Reduction Program at (360)407-6700 (voice) or 711 or (800) 833-6388 (TTY). Table of Contents Introduction ....................................................................................................................................iii Section 1 Laboratory Hazardous Waste Management ...........................................................1 Designating Dangerous Waste................................................................................................1 Counting Wastes .......................................................................................................................8 Treatment by Generator...........................................................................................................12 -
The Application of Controlled Radical Polymerization Processes on the Graft Copolymerization of Hydrophobic Substituents Onto Guar Gum and Guar Gum Derivatives
Louisiana State University LSU Digital Commons LSU Doctoral Dissertations Graduate School 2007 The pplica ation of controlled radical polymerization processes on the graft copolymerization of hydrophobic substituents onto guar gum and guar gum derivatives Veronica Holmes Louisiana State University and Agricultural and Mechanical College, [email protected] Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_dissertations Part of the Chemistry Commons Recommended Citation Holmes, Veronica, "The ppa lication of controlled radical polymerization processes on the graft opoc lymerization of hydrophobic substituents onto guar gum and guar gum derivatives" (2007). LSU Doctoral Dissertations. 3220. https://digitalcommons.lsu.edu/gradschool_dissertations/3220 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Doctoral Dissertations by an authorized graduate school editor of LSU Digital Commons. For more information, please [email protected]. THE APPLICATION OF CONTROLLED RADICAL POLYMERIZATION PROCESSES ON THE GRAFT COPOLYMERIZATION OF HYDROPHOBIC SUBSTITUENTS ONTO GUAR GUM AND GUAR GUM DERIVATIVES A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College In partial fulfillment of the Requirements for the degree of Doctor of Philosophy In The Department of Chemistry By Veronica Holmes B.S., Southern University A&M, Baton Rouge, LA, 1999 May, 2007 Acknowledgements My matriculation through graduate school would not have been possible without the support and guidance of Dr. William H. Daly. His kindness and patience during my graduate endeavors has been unprecedented. Along with the support of past and present graduate students in our research lab, I have had an excellent support system for the duration of time I have spent with this research. -
Ceric Ammonium Nitrate (CAN) Catalyzed Baeyer-Villiger Oxidation of Carbonyl Compounds, Specially 20-Oxosteroids
Indian Journal of Chemistry Vol. 43B, June 2004, pp . 1275-1281 Ceric ammonium nitrate (CAN) catalyzed Baeyer-Villiger oxidation of carbonyl compounds, specially 20-oxosteroids Papori Goswami, Saroj Hazarika, Archana M Das & Pritish Chowdhury* Natural Products Chemistry Division, Regional Research Laboratory, Jorhat 785006, India e-mail: [email protected] Received 4 February 2003; accepted (revised) 10 December 2003 The role of ceric ammonium nitrate (CAN) as an effective catalyst in the peracid induced Baeyer-Villiger oxidation of carbonyl compounds with special reference to steroids has been demonstrated. IPC: Int.C1.7 C 07 K 1/00 Ceric ammonium nitrate (CAN) finds application in temperature even when kept for more than 48 hr. Fur synthetic organic chemistry for various chemical ther, GLC experiment confirmed 40-55% conversion 2 transformations, viz., nitration 1, nitroacetamidation , of benzophenone 12 to phenyl benzoate 12a in 5 hr complex formation with various alcohols3 etc. Its role when CAN was used as a catalyst along with peracid as single electron oxidant has been reported in a num whereas only 8% conversion was observed in the ab 4 8 ber of publications including some recent reviews - . sence of CAN when kept for more than 24 hr. During CAN-induced oxidative radical transformations of our investigation, we also found that for all the cases 9 steroids have also been reported . We too have re (substrates 5-8, 10, 11, 13-15) the oxidation furni shed ported lO the catalytic action of CAN in the esterifica only one isomer viz. 5a-8a, lOa, lla, 13a-15a as con tion of carboxylic acids in very high yield . -
Quinone Formation Via Ceric Ammonium Nitrate Oxidations of 2-Alkyl-1,4-Dialkoxybenzenes
Quinone Formation via Ceric Ammonium Nitrate Oxidations of 2-Alkyl-1,4-dialkoxybenzenes by Alexander Linwood Simmons April, 2016 Director of Thesis: Brian E. Love, PhD Major Department: Chemistry Quinones are cyclohexadiendiones that have a variety of uses ranging from medical applications to synthetic building blocks.1 Medicinal applications stem from the potent biological activity (e.g. antitumor and antibiotic) these compounds and some derivatives possess.2, 3 The most common preparation method to access these compounds is oxidative demethylation of hydroquinone dimethyl ethers (1, R1=R3: Me) typically using ceric ammonium nitrate (CAN) as seen in Figure 1. Oxidation using CAN can yield a product mixture of the (mono)quinone (2) and the symmetric dimeric quinone (3). Previous work4, 5 in our group has resulted in the development of several protocols for altering the monoquinone to diquinone ratio by altering reaction conditions (e.g. substrate concentration, mode of addition, etc.). The current focus further explores manipulation of this ratio and reaction efficacy through substrate solubility and cerium coordination. We will discuss how ether linkages of various hydrophobicities and coordination modes change product outcome and if altering a single ether linkage (R1) or both linkages (both R1 and R3) affect the product ratio. 1 2 3 Figure 1 – General Substrate Reaction Quinone Formation via Ceric Ammonium Nitrate Oxidations of 2-Alkyl-1,4-dialkoxybenzenes A Thesis Presented To the Faculty of the Department of Chemistry East Carolina University In Partial Fulfillment of the Requirements for the Degree Master of Science in Chemistry by Alexander Linwood Simmons April, 2016 © Alexander Linwood Simmons, 2016 Quinone Formation via Ceric Ammonium Nitrate Oxidations of 2-Alkyl-1,4-dialkoxybenzenes by Alexander Linwood Simmons Approved by: Director of Thesis: ____________________________________________________________ Brian E. -
S.T.E.T.Women's College, Mannargudi Semester Iii Ii M
S.T.E.T.WOMEN’S COLLEGE, MANNARGUDI SEMESTER III II M.Sc., CHEMISTRY ORGANIC CHEMISTRY - II – P16CH31 UNIT I Aliphatic nucleophilic substitution – mechanisms – SN1, SN2, SNi – ion-pair in SN1 mechanisms – neighbouring group participation, non-classical carbocations – substitutions at allylic and vinylic carbons. Reactivity – effect of structure, nucleophile, leaving group and stereochemical factors – correlation of structure with reactivity – solvent effects – rearrangements involving carbocations – Wagner-Meerwein and dienone-phenol rearrangements. Aromatic nucleophilic substitutions – SN1, SNAr, Benzyne mechanism – reactivity orientation – Ullmann, Sandmeyer and Chichibabin reaction – rearrangements involving nucleophilic substitution – Stevens – Sommelet Hauser and von-Richter rearrangements. NUCLEOPHILIC SUBSTITUTION Mechanism of Aliphatic Nucleophilic Substitution. Aliphatic nucleophilic substitution clearly involves the donation of a lone pair from the nucleophile to the tetrahedral, electrophilic carbon bonded to a halogen. For that reason, it attracts to nucleophile In organic chemistry and inorganic chemistry, nucleophilic substitution is a fundamental class of reactions in which a leaving group(nucleophile) is replaced by an electron rich compound(nucleophile). The whole molecular entity of which the electrophile and the leaving group are part is usually called the substrate. The nucleophile essentially attempts to replace the leaving group as the primary substituent in the reaction itself, as a part of another molecule. The most general form of the reaction may be given as the following: Nuc: + R-LG → R-Nuc + LG: The electron pair (:) from the nucleophile(Nuc) attacks the substrate (R-LG) forming a new 1 bond, while the leaving group (LG) departs with an electron pair. The principal product in this case is R-Nuc. The nucleophile may be electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged. -
CHEMICAL KINETICS Pt 2 Reaction Mechanisms Reaction Mechanism
Reaction Mechanism (continued) CHEMICAL The reaction KINETICS 2 C H O +→5O + 6CO 4H O Pt 2 3 4 3 2 2 2 • has many steps in the reaction mechanism. Objectives ! Be able to describe the collision and Reaction Mechanisms transition-state theories • Even though a balanced chemical equation ! Be able to use the Arrhenius theory to may give the ultimate result of a reaction, determine the activation energy for a reaction and to predict rate constants what actually happens in the reaction may take place in several steps. ! Be able to relate the molecularity of the reaction and the reaction rate and • This “pathway” the reaction takes is referred to describle the concept of the “rate- as the reaction mechanism. determining” step • The individual steps in the larger overall reaction are referred to as elementary ! Be able to describe the role of a catalyst and homogeneous, heterogeneous and reactions. enzyme catalysis Reaction Mechanisms Often Used Terms •Intermediate: formed in one step and used up in a subsequent step and so is never seen as a product. The series of steps by which a chemical reaction occurs. •Molecularity: the number of species that must collide to produce the reaction indicated by that A chemical equation does not tell us how step. reactants become products - it is a summary of the overall process. •Elementary Step: A reaction whose rate law can be written from its molecularity. •uni, bi and termolecular 1 Elementary Reactions Elementary Reactions • Consider the reaction of nitrogen dioxide with • Each step is a singular molecular event carbon monoxide. -
Aromatic Nucleophilic Substitution Reaction
Aromatic Nucleophilic Substitution Reaction DR. RAJENDRA R TAYADE ASSISTANT PROFESSOR DEPARTMENT OF CHEMISTRY INSTITUTE OF SCIENCE, NAGPUR Principles There are four principal mechanisms for aromatic nucleophilic substitution which are similar to that of aliphatic nucleophilic substitution. (SN1, SN2, SNi, SET Mechanism) 1. SNAr Mechanism- addition / elimination CF3, CN, CHO, COR, COOH, Br, Cl, I Common Activating Groups for NAS Step [1] Addition of the nucleophile (:Nu–) to form a carbanion Addition of the nucleophile (:Nu–) forms a resonance-stabilized carbanion with a new C – Nu bond— three resonance structures can be drawn. • Step is rate-determining • Aromaticity of the benzene ring is lost Step [2] loss of the leaving group re-forms the aromatic ring. • This step is fast because the aromaticity of the benzene ring is restored. ? Explain why a methoxy group (CH3O) increases the rate of electrophilic aromatic substitution, but decreases the rate of nucleophilic aromatic substitution. 2.ArSN1 Mechanism- elimination /addition • This mechanism operates in the reaction of diazonium salts with nucleophiles. •The driving force resides in the strength of the bonding in the nitrogen molecule that makes it a particularly good leaving group. 3.Benzyne Mechanism- elimination /addition Step [1] Elimination of HX to form benzyne Elimination of H and X from two adjacent carbons forms a reactive benzyne intermediate Step [2] Nucleophilic addition to form the substitution product Addition of the nucleophile (–OH in this case) and protonation form the substitution product Evidence for the Benzyne Mechanism Trapping in Diels/Alder Reaction O O B E N Z Y N E C C O O O D i e l s / A l d e r O N H 3 N N Dienophile Diene A d d u c t Substrate Modification – absence of a hydrogens LG Substituent Substituent No Reaction Base Isotopic Labeling LG Nu H Nu Structure of Benzyne • The σ bond is formed by overlap of two sp2 hybrid orbitals. -
Elimination Reactions Are Described
Introduction In this module, different types of elimination reactions are described. From a practical standpoint, elimination reactions widely used for the generation of double and triple bonds in compounds from a saturated precursor molecule. The presence of a good leaving group is a prerequisite in most elimination reactions. Traditional classification of elimination reactions, in terms of the molecularity of the reaction is employed. How the changes in the nature of the substrate as well as reaction conditions affect the mechanism of elimination are subsequently discussed. The stereochemical requirements for elimination in a given substrate and its consequence in the product stereochemistry is emphasized. ELIMINATION REACTIONS Objective and Outline beta-eliminations E1, E2 and E1cB mechanisms Stereochemical considerations of these reactions Examples of E1, E2 and E1cB reactions Alpha eliminations and generation of carbene I. Basics Elimination reactions involve the loss of fragments or groups from a molecule to generate multiple bonds. A generalized equation is shown below for 1,2-elimination wherein the X and Y from two adjacent carbon atoms are removed, elimination C C C C -XY X Y Three major types of elimination reactions are: α-elimination: two atoms or groups are removed from the same atom. It is also known as 1,1-elimination. H R R C X C + HX R Both H and X are removed from carbon atom here R Carbene β-elimination: loss of atoms or groups on adjacent atoms. It is also H H known as 1,2- elimination. R C C R R HC CH R X H γ-elimination: loss of atoms or groups from the 1st and 3rd positions as shown below. -
Optimization of Ceric Ammonium Nitrate Initiated Graft Copolymerization of Acrylonitrile Onto Chitosan
Journal of Water Resource and Protection, 2011, 3, 380-386 doi:10.4236/jwarp.2011.36048 Published Online June 2011 (http://www.scirp.org/journal/jwarp) Optimization of Ceric Ammonium Nitrate Initiated Graft Copolymerization of Acrylonitrile onto Chitosan Arumugam Shanmugapriya1, Ramya Ramammurthy2, Venkatachalam Munusamy3 , Sudha N. Parapurath4 1Bharathiar University, Coimbatore, Tamil Nadu, India 2Department of Chemistry, Manonmaniam Sundaranar University, Tirunelveli, Tamil Nadu, India 3Department of Chemistry, Dravidian University, Kuppam, Andhra Pradesh, India 4DKM College, Thiruvalluvar University, Vellore, Tamil Nadu, India E-mail: [email protected] Received March 14, 2011; revised April 21, 2011; accepted May 25, 2011 Abstract In the present work, graft copolymerization of polyacrylonitrile onto chitosan has been carried out in the pre- sence of ceric ammonium nitrate redox initiator. Optimization of grafting of polyacrylonitrile onto chitosan was performed by varying the process parameters such as ceric ammonium nitrate (CAN) concentration, polyacrylonitrile concentration and reaction time to study their influence on percent grafting and grafting ef- ficiency. The optimum reaction conditions obtained for grafting of acrylonitrile onto chitosan were reaction time 55 mins, CAN concentration 1% in Con. HNO3, and polyacrylonitrile concentration 0.75 mol/L. The characterization of the grafted products by means of FTIR, thermal analysis, X-ray diffraction and scanning electron microscopy furnished the evidence of grafting of polyacrylonitrile onto chitosan. Keywords: Chitosan-g-polyacrylonitrile, Ceric ammonium nitrate, Grafting efficiency, Grafting yield 1. Introduction synthetic polymers increased its properties tremendously. Besides these applications chitosan has few drawbacks Chitosan is a unique basic polysaccharide and partially such as acidic solubility, low thermal and mechanical deacetylated polymer of glucosamine obtained after alka- stability. -
FULL PAPER a Self-Assembled Cage with Endohedral Acid Groups Both
FULL PAPER A Self-Assembled Cage with Endohedral Acid Groups both Catalyzes Substitution Reactions and Controls their Molecularity Paul M. Bogie, Lauren R. Holloway, Courtney Ngai, Tabitha F. Miller, Divine K. Grewal, and Richard J. Hooley[a]* [16],[17] Abstract: A self-assembled Fe4L6 cage complex internally decorated many possibilities in controlled biomimetic catalysis, above with acid functions is capable of accelerating the thioetherification of and beyond simply increasing the effective concentration of activated alcohols, ethers and amines by up to 1000-fold. No product bound substrate. The incorporation of active functions in an inhibition is seen, and effective supramolecular catalysis can occur enclosed space enables reagent-controlled reactions to take with as little as 5 % cage. The substrates are bound in the host with place in enclosed cavities, as opposed to cycloadditions[18]-[20] or up to micromolar affinities, whereas the products show binding that is unimolecular rearrangements, [21],[22] which are still the most an order of magnitude weaker. Most importantly, the cage host alters common reactions studied in synthetic hosts. By internalizing the molecularity of the reaction: whereas the reaction catalyzed by reactive functional groups in a cage, the effect of substrate simple acids is a unimolecular, SN1-type substitution process, the rate binding on nucleophilic substitution reactions can be investigated. of the host-mediated process is dependent on the concentration of nucleophile. The molecularity of the cage-catalyzed reaction is substrate-dependent, and can be up to bimolecular. In addition, the catalysis can be prevented by a large excess of nucleophile, where substrate inhibition dominates, and the use of tritylated anilines as substrates causes a negative feedback loop, whereby the liberated product destroys the catalyst and stops the reaction.