Photolysis of isobutene at 185 nm

On photolysis at 185 nm in a mercury-free system, isobutene, 2-methyl propene, yields hydrogen. thirty-one hydrocarbon products and a solid polymer (table 1). The product yields are decreased by addition of inert gases, or by increasing the reactant pressure. Yields are also reduced by the addition of oxygen, which affects some products similarly but others to a greater extent than nitrogen, Using this effect to distinguish between products formed by molecular and free radical reactions, a primary scheme of six reactions is postulated and the primary quantum yields determined (table 2). The major reactions are cleavage of the C—C and the β C—H bonds in the ratio 1.2 : 1. The overall quenching is attributed to deactivation of an excited intermediate state, the lifetime of which has been estimated. The intermediate is thought to be a Rydberg state.