Isotopic Exchange and the Replacement of Hydrogen in Organic Compounds

Hydrogen replacement reactions play an outstanding part in organic chemistry. They include such industrially important processes as halogenation, nitration, sulfona­ tion, alkylation, and direct amination and metallation of organic substances. It is no accident that the data obtained in the investigation of these reactions have been used extensivel y in the solution of a series of fundamental problems in theoretical organ­ ic chemistry and this tendency still exists. Isotopic exchanges of hydrogen also belong to this group of chemical conversions. They have attracted considerable attention as they are the simplest and, to some ex­ tent, models of hydrogen replacement reactions, which are convenient for elucidating the mechanism of hydrogen replacement and the effects of interaction between atoms in organic molecules. The mechanisms of hydrogen replacement reactions are examined in this mono­ graph and the most space is allocated to hydrogen isotope exchanges. The mechan­ isms of all the given reactions are interpreted from the point of view of the acid­ base properties of the reagents. In this connection, a large section of the book is de­ voted to a thorough substantiation of the thesis that hydrocarbons participating in the given reactions act as acids or bases. Problems of acid-base catalysis and the mech­ anism of acid -base interaction are also discussed. Thus, a considerable part of the book is concerned with problems of the theory of acids and bases.

Section I. Types of Reagents and Reactions.- 1. Oxidizing and Reducing Agents.- 2. Acids and Bases.- 3. Acidlike Substances.- 4. Nucleophilic and Electrophilic Reagents.- 5. Wider Definitions of Acids and Bases.- 6. Relative and Approximate Nature of the Classification of Reagents.- 7. Donor-acceptor Interaction.- 8. Heterolytic and Homolytic Reactions.- 9. Place of Hydrogen Exchange Among Other Reactions.- 10. Summary.- Literature Cited.- Section II. Acid-Base Catalysis of Hydrogen Exchange.- 1. Introduction.- 2. Comparison of the Rates of Hydrogen Exchange with Amphoteric and Protophilic Solvents.- 3. Comparison of the Rates of Hydrogen Exchange with Amphoteric and Protogenic Solvents.- 4. Effect of the Dielectric Constant of the Solvent and the Polarity of Its Molecules on the Hydrogen Exchange Rate.- 5. Effect of the Substrate and Catalyst Charge on the Hydrogen Exchange Rate.- 6. Effect of Dual Reactivity of a Substance on Hydrogen Exchange.- A. Acceleration of Acid Exchange by a Base.- B. Acceleration of Basic Exchange by an Acid.- C. Inversion of Relative Rates of Hydrogen Exchange with Amphoteric and Protophilic Solvents.- D. Inhibition of Acid Hydrogen Exchange by an Acid.- 7. Effect of Steric Hindrance on Hydrogen Exchange.- 8. Decrease in the Activity of a Catalyst on Its Reaction with the Substrate.- 9. Activation of a Catalyst by a Change of Solvent.- 10. Catalytic Activity of Complexes of Hydrogen Acids with Acidlike Substances in Hydrogen Exchange.- 11. Brønsted’s Relation in Hydrogen Exchange.- A. Rate and Equilibrium of Protolyte Ionization.- B. Brønsted’s Relation in Hydrogen Exchange.- 12. Hammett’s Relation in Hydrogen Exchange.- A. Hammett’s Acidity Function.- B. Reaction Rate and Acidity Function.- C. Hammett’s Relation in Hydrogen Exchange.- 13. Salt Effect in Hydrogen Exchange.- 14. Acid-Base Catalysis of Hydrogen Exchange in H-H, B-H, N-H, As-H, P-H, O-H, and S- H Bonds.- A. Exchange in H-H Bond.- B. Exchange in B-H Bond.- C. Exchange in N-H Bond.- D. Exchange in P-H Bond.- E. Exchange in As-H Bond.- F. Exchange in O-H Bond.- G. Exchange in S-H Bond.- 15. Heterogeneous Acid-Base Hydrogen Exchange.- 16. Summary.- Literature Cited.- Section III. Hydrocarbons as Acids and Bases.- Literature Cited.- 1, Hydrocarbons as Acids.- 1. Metallation of Hydrocarbons.- A. Reactions of Hydrocarbons with Alkali Metals.- B. Reactions of Hydrocarbons with Bases.- 2. Saltlike Nature of Organoalkali Compounds.- A. Electrical Conductivity of Solutions.- B. Ionic Reactions.- 3. Carbanions.- A. Formation of Carbanions.- B. Spectra of Carbanions.- 4. Comparison of the Strengths of Carbo Acids by Metallation Reactions.- A. General Comparison.- B. Classes of Hydrocarbons.- 5. Isotopic Exchange of Hydrogen.- A. Amphoteric Solvents.- B. Liquid Ammonia.- C. Liquid Exchange Between Hydrocarbons.- 6. Isomerization of Unsaturated Hydrocarbons.- A. Nature of Reaction.- B. Isomerization of Hydrocarbons by Bases.- C. Rules of Isomerization.- 7. Alkylation by Olefins.- A. Michael and Analogous Reactions.- B. Alkylation of Amines and Ammonia by Olefins.- C. Alkylation of Aromatic Hydrocarbons.- D. Dimerization of Olefins.- 8. Summary.- Literature Cited.- 2. Hydrocarbons as Bases.- 1. Introduction.- 2. Carbonium Ions.- A. Rupture of a Bond Between Carbon and an Electronegative Atom or Group.- B. Exchange Between a Carbonium Ion and a Hydrocarbon.- C. Elimination of a Hydride Ion.- D. Addition of a Proton to an Unsaturated Hydrocarbon.- E. Addition of a Carbonium Ion to an Aromatic Hydrocarbon.- F. Detection of a Carbonium Ion by Deuterium Exchange.- 3. Equilibrium Reactions of Hydrocarbons with Acids.- A. Introduction.- B. Liquid Hydrogen Fluoride.- C. Sulfuric Acid.- D. Hydrogen Chloride and Bromide.- E. Carbonium Salts of Haloaluminic Acids.- F. Carboxylic Acids.- 4. Equilibrium Reactions of Basic Hydrocarbons with Acidlike Substances.- A. Introduction.- B. Sulfur Dioxide.- C. Halogens.- 5. Irreversible Reactions of Basic Hydrocarbons with Acidlike Substances.- 6. Isotopic Exchange of Hydrogen Between Hydrocarbons and Acids.- A. Introduction.- B. Aromatic Hydrocarbons.- C. Unsaturated Aliphatic Hydrocarbons.- D. Saturated Hydrocarbons.- 7. Summary.- Literature Cited.- Conclusion.- Section IV. Mechanism of Acid-Base Interaction.- 1. Brønsted’s Theory of Acids and Bases.- 2. Deviations from Brønsted’s Theory and the Need for Development of the Latter.- 3. Noncoulombic Interaction in Solutions of Acids and Salts.- 4. Acid-Base Reactions in Aprotic Solvents.- A. Application of Brønsted’s Theory.- B. Inadequacy of Brønsted’s Theory.- 5. N. A. Izmailov’s Theory of the Dissociation of Acids and Bases.- A. Comparison of the Strengths of Acids in Different Solvents.- B. Reasons for Deviations from Brønsted’s Theory.- C. N. A. Izmailov’s Theory.- 6. The Role of the Hydrogen Bond in Acid-Base Interaction.- A. Donor-Acceptor Interaction in the Formation of a Hydrogen Bond.- B. Polarity of Molecular Compounds of Acids with Bases.- C. Displacement of Bond Vibration Frequency in the Infrared Absorption Spectrum on the Formation of a Hydrogen Bond.- D. Other Manifestations of a Hydrogen Bond.- 7. Range of Protolytic Reactions.- 8. Definitions of Acids and Bases.- 9. Summary.- Literature Cited.- Section V. Mechanisms of Hydrogen Replacement Reactions.- 1. Replacement of Hydrogen by Reaction with a Nucleophilic Reagent.- 1. Attack of the Reagent on the Hydrogen Atom of a CH Bond.- A. Electrophilic Substitution Hypothesis and Criticism of It.- B. Metallation - A Protophilic Substitution Reaction.- 2. Attack of the Reagent on the Carbon Atom of a CH Bond.- A. General Principles.- B. Chichibabin’s Reaction.- C. Replacement of Hydrogen in Nitro Compounds.- D. Replacement of Hydrogen in Hydrocarbons.- 3. Summary.- Literature Cited.- 2. Replacement of Hydrogen by Reaction with an Electrophilic Reagent.- 1. Orientation Rules.- 2. Relation of the Reactivity of a Substance to the “Activity” of the Reagent.- 3. Partial Rate Factors of the Replacement of Hydrogen Atoms in an Aromatic Ring.- A. Definition.- B. Relation Between the “Activity” of the Reagent and the “Selectivity” of the Replacement.- C. Change in the Reactivity of a Substance in Catalysis.- D. Calculation of the Relative Reactivity of Substances from Partial Rate Factors.- 4. Reason for Selectivity of Replacement.- 5. Role of the Steric Factor in the Replacement of Hydrogen.- 6. Participation of Associative and Ionization Processes in Hydrogen Replacement Reactions.- 7. Summary.- Literature Cited.- 3. Mechanisms of Hydrogen Exchange.- 1. Comparison of Rules of Hydrogen Exchange and Other. Replacements of Hydrogen in Aromatic Compounds.- A. Basic Hydrogen Exchange.- B. Acid Hydrogen Exchange.- 2. Mechanisms of Hydrogen Exchange.- A. A. I. Brodskii’s Classification.- B. Associative and Ionization Mechanisms of Hydrogen Exchange.- 3. Summary.- Literature Cited.- Conclusion.- Appendix: Preparation of Deuterated Organic Compounds.- 1. Introduction.- 2. Methods of Preparing Deuterated Organic Compounds.- 3. Synthesis of Deuterated Organic Compounds.- A. Reduction.- B. Hydration and Hydrolysis.- C. Ammonolysis.- D. Condensation.- E. Decarboxylation.- 4. Isotopic Exchange of Hydrogen.- A. Hydrogen Exchange with Heavy Water and Deuteroalcohol.- B. Hydrogen Exchange with Deuterosulfuric Acid.- D. Hydrogen Exchange with Liquefied Gases.- 5. Comparison of Methods of Preparing Deuterium Compounds.- Literature Cited.