On the ozonolysis of indane and tetralin as well as some dimethyl homologues in connection with the reactivity of the bonds in the ring system: (with reference to the so‐called Mills‐Nixon effect)

Abstract

AbstractIn the ozonolysis of 4,7‐dimethylindane the aliphatic dicarbonyl compounds methylglyoxal and glyoxal are formed in a combined yield of 0.1 mol of dicarbonyl compound per mol of dimethylindane. The molecular ratio glyoxal: methylglyoxal is 1.57: 1.In the ozonolysis of 5,6‐dimethylindane the aliphatic dicarbonyl compounds methylglyoxal and dimethylglyoxal (diacetyl) are formed in a combined yield of 0.05 mol per mol of dimethylindane. The molecular ratio diacetyl: methylglyoxal is 3.5: 1.From the above it follows that each of the six carbon‐carbon bonds of the aromatic six‐membered ring in 4,7‐ and 5,6‐dimethylindane respectively can react with ozone. There is no question of a “fixation” of the double bonds in the aromatic six‐membered ring. From the molecular proportion of the dicarbonyl compounds it follows that during the action of ozone on 4,7‐ and 5,6‐dimethylindane respectively there is a marked preference for the attack of the common carbon‐carbon bond of the ring system. This common carbon‐carbon bond displays towards ozone a stronger double‐bond character than do the adjacent carbon‐carbon bonds in the aromatic ring. This result is contrary to the theory of Mills and Nixon, but is qualitatively in agreement with the calculations of Longuett‐Higgins and Coulson.In the ozonolysis of 5,8‐dimethyltetralin the aliphatic dicarbonyl compounds glyoxal and methylglyoxal are formed in a combined yield of 0.07 mol per mol of dimethyltetralin. The molecular ratio methylglyoxal: glyoxal is about 3: 1. In the ozonolysis of 6,7‐dimethyltetralin the aliphatic dicarbonyl compounds methylglyoxal and dimethylglyoxal are formed in a combined yield of 0.09 mol per mol of dimethyltetralin. The molecular ratio methylglyoxal: dimethylglyoxal is 1.1: 1.From these findings it follows that each of the six carbon‐carbon bonds of the aromatic six‐membered ring in 5,8‐ or 6,7‐dimethyltetralin can react with ozone.There is no marked preference for the attack of the common carbon‐carbon bond, as compared with the attack of the adjacent carbon‐carbon bonds in the aromatic six‐membered ring. This result is contrary to the theory of Mills and Nixon.To check the analytic method used by us, we examined the ozonolysis of p‐xylene and of 1,2,4,5‐tetramethylbenzene (durene).In the ozonolysis of p‐xylene, methylglyoxal and glyoxal are expected to be formed in the molecular ratio 2: 1; the proportion found was 2.15: 1.In the ozonolysis of durene, methylglyoxal and dimethylglyoxal are expected to be formed in the molecular ratio 2: 1; the proportion found was 1.93: 1.