exclusively in such reactions there is thought to be competition between the elimination and the substitution routes the former producing the conjugated diene containing polymer the latter an allylic ester containing polymer as indicated below str9 for the purpose of this invention reaction 7 must be repressed the conjugated diene containing butyl rubbers of this invention may be cured by a variety of methods as taught in ser no 228 728 which also is incorporated herein by reference as are the methods of covulcanizing these rubbers with other general purpose rubbers suitable carboxylic acids useful in the present invention are c 5 to c 13 monocarboxylic acids known as neo acids enjay chemical co which are trialkyl acetic acids e g neopentanoic acid trimethyl acetic acid neo heptanoic acid dimethyl n propyl acetic acid neo decanoic acid and mixtures of the trialkyl acetic acids having 5 to 13 carbon atoms other monocarboxylic acids useful in this invention are the aliphatic and naphthenic carboxylic acids having about 2 to 20 carbon atoms a ring substituted aromatic carboxylic acid among the most preferred are 2 ethylhexanoic and naphthenic acids the salt and acid used in this method generally are but need not be the same e g if the naphthenate of group iib metal is used it would usually be used in conjunction with naphthenic acid while it is believed that virtually any carboxylic acid would be suitable in the present invention for use with the metals of groups ib iib iva.