Organohalogen compounds. Part II. The reactions of 2,3-dimethyl-buta-1,3-diene with chlorine and with iodine monochloride

Abstract

The reaction of 2,3-dimethylbuta-1,3-diene with an equimolar amount of chlorine in carbon tetrachloride at –20 °C gives mainly trans-1,4-dichloro-2,3-dimethylbut-2-ene and 2-chloromethyl-3-methylbuta-1,3-diene. Chlorination in methylene chloride at –78 °C with gaseous chlorine yields initially a mixture of the same compounds and 1-chloro-2,3-dimethylbuta-1,3-diene in comparable amounts, together with the hydrogen chloride adducts 3-chloro-2,3-dimethylbut-1-ene and 1-chloro-2,3-dimethylbut-2-ene; further chlorination affords 1-chloro-3-chloromethyl-2-methylbuta-1,3-diene, 2,3-bis(chloromethyl)buta-1,3-diene, and 1,4-dichloro-2,3-bis(chloromethyl)but-2-ene and then a mixture of trichlorides, 1,2,3,4-tetrachloro-2-chloromethyl-3-methylbutane, and unidentified polychlorides. Bromination of trans-1,4-dichloro-2,3-dimethylbut-2-ene followed by dehydrobromination of the adduct gives 1,4-dichloro-2,3-dimethylbuta-1,3-diene in high yield. The reaction of 2,3-dimethyl-buta-1,3-diene with iodine monochloride affords, as the only identified product, 1,2,3,4-tetrachloro-2,3-dimethylbutane.