Abstract The effect of ring size on the reactivity of C 5 to C 12 cycloalkenes in the copper (II) oxide catalysed and dibenzoyl peroxide initiated addition reaction with ethyl cyanoacetate was determined at 90 C using the method of competition reactions. cis-Cyclooctene exhibited the highest and cyclohexene as well as cis-cyclodecene the lowest reactivity. Relative reactivities of C 5, C 6 cis-C 7 and cis-C 8 cycloalkenes could be correlated with ...