Rates of termination of radicals in solution. VII. Allylic radicals

The rate constants for bimolecular decay of allyl, 2-methallyl, and cis- and trans-1-methallyl radicals in liquid propene, isobutene, and cis- and trans-2-butene, respectively, have been determined over a wide temperature range from near the boiling points of the solvents to about - 120° using the esr-rotating sector technique. The values, which range from 10^9 to 10^(10) M^(-1) sec^(-1), were compared with the encounter rate constants calculated from density and viscosity data. We conclude that the self-termination of allyl, 2-methallyl, and trans-1-methallyl radicals fits the diffusion-controlled model. However, the rate constant for the cis-1-methallyl radical is unexpectedly high at the higher temperatures. The viscosities of liquid propene, isobutene, and cis- and trans-2-butene between their boiling points and - 100° are reported.