The kinetics and mechanisms of aromatic halogen substitution. Part XXIV. The stereochemistry of addition of chlorine to naphthalene

Abstract

The reaction of chlorine with naphthalene in acetic acid gives products of substitution (mainly 1-chloronaphthalene); products of addition of chlorine (mainly naphthalene-α-tetrachloride, m. p. 182°); and other products of addition (mainly an acetoxytrichloride). In the presence of added lithium chloride, the mixture of tetrachlorides contains a major proportion of the stereoisomeric δ-isomer, m. p. 96°. Light-catalysed addition in carbon tetrachloride gives a mixture of isomers, the least soluble being naphthalene-γ-tetrachloride, m. p. 134°, and the major part of the remainder being a new isomer, naphthalene-ε-tetrachloride, m. p. 85–87°. The configurations and conformations of the γ-, δ-, and ε-tetrachlorides and of the acetoxytrichloride have been established by proton magnetic resonance spectroscopy. The results establish that the α-tetrachloride is not formed through capture of a carbonium ionic intermediate by chloride ion from the environment.