Naphthalene tetrachlorides and related compounds. Part V. Chlorination of 1,5-dichloronaphthalene; conformations affected by intramolecular non-bonding repulsions

Abstract

The chlorination of 1,5-dichloronaphthalene in chloroform or in dichloromethane is heterolytic in character, but gives little or no trichloronaphthalene. The main tetrachloride product is 1,1,r-2,t-3,c-4,5-hexachlorotetralin, previously thought to be its t-4-isomer. The latter compound has been prepared by isomerisation of the former with aluminium trichloride. The structures have been established by using ¹H n.m.r. spectroscopy together with reactions with aluminium trichloride and with sodium methoxide. The former tetrachloride exists in a deformed conformation as the result of intramolecular non-bonding repulsions. trans-1,2,4,8-Tetrachloro-1,2-dihydronaphthalene is an intermediate in the chlorination.