A general inductive ef€ ect, which is described as manifesting itself in a feeble electron- release character, is attributed to alkyl groups.'This effect is considered to increase with the amount of branching in the order: methyl, ethyl, i-propyl, t-butyl, and with increasing length of a normal alkyl chain from methyl to about n-propyl or n-butyl, where a maximum is reached beyond which the effect is usually not transmitted. The nature and order of the effect are ...
[Tolbert, Laren M.; Khanna, Rajive K.; Popp, Ann E.; Gelbaum, Leslie; Bottomley, Lawrence A. Journal of the American Chemical Society, 1990 , vol. 112, # 6 p. 2373 - 2378]