UNIMOLECULAR SUBSTITUTIONS AND RELATED REACTIONS

In this chapter we take up unimolecular and borderline substitutions and discuss carbocations, carbanions, and carbenes, three of the important reactive organic intermediates. 

1 LIMITING UNIMOLECULAR NUCLEOPHILIC REACTIONS. KINETICS AND STEREOCHEMISTRY1 

Diphenylchloromethane (benzhydryl chloride, 1), when dissolved in solvents such as aqueous ethanol, aqueous acetone, acetic acid, or formic acid, undergoes substitution of chloride by a nucleophilic group derived from the solvent. 

Equation 5.1, in which SOH stands for a molecule of some hydroxylic solvent, illustrates the process. This type of reaction, where the solvent takes the role of the 

1 Unimolecular substitutions are discussed in detail in the following sources (a) C. A. Bunton, Nucleophilic Substitution at a Saturated Carbon Atom, Elsevier, Amsterdam, 1963 (b) C. K. Ingold, Structure and Mechanism in Organic Chemistry, 2nd ed., Cornell University Press, Ithaca, N.Y., 1969 (c) A. Streitwieser, Jr., Solvolytic Displacement Reactions, McGraw-Hill, New York, 1962 (d) E. R. Thornton, Solvolysis Mechanisms, Ronald Press, New York, 1964. 

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