AbstractThe phenomenon mentioned in an earlier paper,viz.that a methyl group inortho‐xylene derivatives may behave as a larger substituent than the methyl group in comparablepara‐xylene or toluene derivatives, has been investigated more in detail with the aid of deacylation rates, ultra‐violet absorption spectra, molecular refractions, and basic strengths. The phenomenonper sehas been confirmed by this work. Naturally, however, it does not always manifest itself to the same degree; various factors play their part in this respect.On the strength of the data collected, the order of steric effects of methyl (ene) groups found byArnoldand co‐workers has to be modified as follows: CH2(in o‐xylyl)>CH2(in a 6‐membered ring)>CH2(in tolyl)>CH2(in a 5‐m