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Kendall, F. H. (1958) Reactions of ozone with natural hevea and acrylonitrile-butadiene rubbers: studies of hydrolysis reactions of substituted p-nitroso-dialkylanilines. Doctoral thesis, Sir John Cass College.
Part I.
The nature of wax films used to protect vulcanised rubber against ozone has been studied and methods developed for measurement of film thickness. An improved ozone resistance test apparatus has been designed and built. The physical changes that occur when ozone reacts with unvulcanised and unstretched vulcanised rubber have been studied and the products from the reaction were investigated by infra-red spectrum analysis. To minimise the effects of excess ozone on initial products, a technique was developed for exposing to ozone a continuously spreading monolayer of acrylo-nitrile butadiene copolymer, which was collected and examined by infra-red analysis. Preliminary experiments with monolayers showed that the progress of ozonisation could be followed by surface area/pressure measurements. The results are considered in relation to observations on the ozonisation of simple unsaturated compounds and it is concluded that during ozonisation spontaneous scission at the carbon double-bond position occurs. The presence of an oxidative chain reaction is also indicated but this does not seem to contribute to the processes responsible for characteristic ozone cracking.
Part II.
The reaction between sodium hydroxide and p-nitroso-dimethyl aniline has been shown to follow second order kinetics. The Arrhenius constants have been determined for p-nitroso-dimethylaniline and six other substituted p-nitroso-dialkylanilines. The effect of substituents in the aromatic ring on the reaction rate has been related to Hammett substituent constants and it has been shown that substitution of n-propyl for methyl on the anilinium nitrogen is associated with a significant change in entropy of activation. A reaction mechanism based on current theories has been postulated to account for the observations, and the significance of other activating groups in nucleophilic hydrolysis reactions is discussed.
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