Process and apparatus for the preparation of 2-chloro-butadiene-1:3

2 - Chlorobutadiene - 1,3 (chloroprene) is prepared by reacting 1,2-dichlorobutene-3 with an 8-10% by weight aqueous alkali metal hydroxide solution in an oxygen-free medium at temperatures above 80 DEG C. in the presence of 0.05-0.1% by weight of a water-soluble emulsifier, calculated on the quantity of aqueous alkali metal hydroxide solution added to the reaction mixture, provided that, when the process is carried out continuously, the 1,2-dichlorobutene-3 is added to the aqueous alkali metal hydroxide solution at such a rate that 1 mole of chloroprene distils off for each mole of 1,2-dichlorobutene-3 added. The emulsifier is a compound which reduces the surface tension of the aqueous alkali solution, has a boiling point above 80 DEG C., is inert to 1,2-dichlorobutene-3 and chloroprene, and does not promote the polymerization of chloroprene. 1-Chlorobutadiene-1,3 is produced as a by-product.