Dehydrochlorination of 2-chloroethanol, 2-chloro-1-propanol, 1-chloro-2-propanol, 2-chloro-2-methyl-1-propanol and 1-chloro-2-methyl-2-propanol

The reactions between a few 1,2-chlorohydrins and sodium hydroxide have been studied and shown to involve a two-step nucleophilic elimination of hydrogen chloride.The data are given for the slow rate-determining step of 2-chloroethanol 1, 2-chloro-1-propanol 2, 1-chloro-2propanol 3, 2-chloro-2-methyl-1-propanol 4 and 1-chloro-2-methyl-2-propanol 5. Compounds 4 and 5 gave 2-methyl-1,2-propanediol as the final product instead of oxiranes given by compounds 1-3.In contrast to some earlier reports the mere water reaction was shown to be almost negligible.In constant ionic strength the base concentration had no effect on the rates whereas at different base concentrations (0.050-0.250 mol dm -3 ) alone the rate of alkaline dehydrochlorination of 1 clearly decreased (10 3 k2, dm 3 mol -1 s -1 : 10.0-8.7,respectively).The rate of 2 at constant base concentration (0.010 mol dm -3 ) and at different ionic strengths (dm 3 mol -1 : 0.010-0.500)decreased also (10 3 k2, dm 3 mol -1 s -1 : 76-65, respectively) indicating that the decrease is mainly due to the change in the ionic strength also in the former case.