Quantitative investigation of the ozonization of ortho‐xylene and of 1,2,4‐trimethyl benzene; a chemical proof of the equivalence of the six cc bonds in the benzene ring

Abstract

Abstract The qualitative results of Levine and Cole on the formation of glyoxal, methyl glyoxal and dimethyl glyoxal in the ozonization of o‐xylene are confirmed. However, we obtained much greater yields of these oxidation products, namely 20‐26% of the theoretical yield. A method has been worked out for determining these aldehydes and ketones in the form of the oximes. The mixture of oximes obtained in the ozonization of o‐xylene consists of 21.0% dimethylglyoxime, 34.2% methylglyoxime and 43.9% glyoxime (averages of 5 experiments). This ratio is in good accordance with the ratio calculated on the basis or the following assumptions: that the six CC bonds in the benzene‐nucleus of o‐xylene are equivalent (the two Kékulé structures contributing each for 50% to the structure of o‐xylene); that the addition of ozone is not affected by steric hindrance of the methyl groups. The ozonization of 1,2,4‐trimethylbenzene has been investigated by means of the same methods. In this case the mixture of oximes consists of 17.9% dimethylglyoxime, 66.2% methylglyoxime and 14.2% glyoxime (average of two experiments). This ratio agrees very well with the ratio calculated on the basis of the assumptions: 1. that the six CC bounds in the benzenering of 1,2,4‐trimethylbenzene are equivalent, 2. that the addition of ozone is not affected by steric hindrance of the CH 3 ‐groups.