Evaluation of the hydrocarbon condensation polymerisation reaction by means of model compounds. II. The reaction of with n‐alkyl chlorides and iodides, and sec‐ and tert‐alkyl bromides

Abstract

AbstractThe title polymerisation involves the reaction in tetrahydrofuran of α‐methylstyrene (M) with lithium in the presence of an alkyl dihalide (RX2) to form copolymers. Replacement of the dihalide by the analogous monohalide RX gives small molecules, the relative amounts of which furnish information on the polymerisation process and the resulting structures of the copolymers. This paper describes the use of n‐alkyl iodides and chlorides, and sec‐ and tert‐bromides in this regard.n‐Alkyl iodides were found to behave in a similar manner to n‐alkyl bromides (Part I) with high yields of the dimer HRM2RH being obtained at 1 : 1 M stoichiometry. On the other hand, n‐alkyl chlorides gave a variety of additional products under these conditions and a structural analysis of these materials showed that they resulted from reactions involving n‐alkyl lithium which was formed by the chloride reacting directly with the lithium. This difference in behaviour is explained in terms of the high strength of the carbon‐chlorine bond and implies that copolymers prepared with dichlorides are less regular than those obtained with dibromides.sec‐ and tert‐bromides also gave a variety of products at equimolar stoichiometry and this was shown to be due to the β‐hydrogen elimination reaction becoming significant. Elimination was most prominent with the tert‐bromides, accounting for about 60% of der termination reaction of the dimer.