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The mechanism for the decomposition of compounds of the type CH,.CH.CH*CHY.X is discussed and the kinetic parameters are correlated with the molecular parameters. Preliminary experiments on the decomposition of 2.5-dihydrothiophen show that for the formation of thiophen and hydrogen, the first-order rate constant is given by kl = * exp(54.800 f 3500/RT) where R = 1.9865 cal deg-l mol-1 [k, = f O e 6 l exp (229,000 i 15,00O/RT) where R = 8-31 43 J mol-1 deg-l].

The pyrolysis of 3-pyrroline in the gas phase has been found to be a unimolecular first-order process, the rate constant being independent of pressure in the range 2-34 torr (267-4533 Nm-2). Hydrogen and pyrrole in equal amounts are the only gaseous products. The rate of reaction and product yields are unaffected by the addition of significant amounts of nitric oxide.The temperature dependence of the rate constants of the reaction over the temperature range 31 7-358" is given by the expression k, = (1.9 f 0.4) x 10l2 exp (44,600 f 241/RT) s-l where R = 1.987 ca( deg-1 mol-1 (k, = (1 a 9 f 0.4) x 10l2 exp (186,600 f 1000/RT) where R = 8.314 J deg-l mol-I). When the Pyrex