GB798889A - Allylic rearrangement of chlorine substituted butenes - Google Patents

Abstract

The invention comprises a process for the allylic rearrangement of 3-chlorbutene-1, 1-chlorbutene-2, 3 : 4-dichlorbutene-1 or 1 : 4 dichlorbutene-2 by contacting the chlorine substituted butene at an elevated temperature with a copper salt in the presence of an organic amine. Suitable salts are cuprous or cupric chlorides, sulphates or acetates, and suitable amounts are between 0.1 and 1 per cent by weight of the anhydrous salt based on the weight of chlorine substituted butene. Suitable organic amines are those which are liquid at normal pressure at the temperature at which the reaction is carried out, e.g. tri-n-butylamine, quinoline, a -picoline, pyridine, o-anisidine, triethanolamine and a C1-C6 monoalkylamine. Preferable amounts of amines are about 2 to 5 times the weight of the copper salt present. The reaction may be carried out by dissolving the copper salt in the warm amine and adding the catalyst mixture to the chlorine substituted butene. Temperatures up to the boiling point of the reaction mixture may be used preferably at atmospheric pressure although increased and reduced pressures may be used. If the reaction mixture is continuously distilled the lower boiling component is continuously removed. If the higher boiling isomer is required, however, the starting material should be heated with the copper salt/organic base catalyst until a substantial amount of the desired product has been obtained, the catalyst should then be removed, for example by flash distillation, or by washing with concentrated hydrochloric acid, and the mixture distilled. The remaining lower boiling isomer may then be reheated. Mixtures of monochlorbutenes with dichlorbutenes can also be used as the starting material. Tests are described illustrating the isomerism of 1-chlorbutene-2 and 3-chlorbutene-1, and 3 : 4-dichlorbutene-1 to 1 : 4 dichlorbutene-2 using copper catalysts in the presence and absence of an amine, and an example given of the conversion of 1-chlorbutene-2 to 3-chlorbutene-1 in the presence of cuprous chloride and a -picoline.