THE MECHANISM AND STEREOCHEMISTRY OF CHLORINATION OF 2,4-DICHLORO-3,,5,6-TRIMETHYLPHENOL AND 2,4-DICHLORO-3,6-DIMETHYLPHENOL

Electrophilic attack of chlorine on 4,6-trichloro-3,5,6-trimethylcyclo hexa-2,4-dienone (2a) gives the trans-pentachloro ketones (3a) and (4a ), while similar reaction of 2,4,6-trichloro-3,6-dimethylcyclohexa-2,4 -dienone (2b) gives the trans-pentachloro ketones (3b) and (4b), resul ting from 2,5- and 4,5-addition of chlorine. The probable stereochemis try of chlorine addition in ketones (3b) and (4b) is determined by chl orination of 2,4-dibromo-3,6-dimethylphenol (6). X-Ray crystal structu res are reported for compounds (3a,b), (7) and (8).