Reaction of H and D atoms with deuterated propylenes

Abstract

Effects of deuterium substitution in propylene on the relative rates of H(D) atom abstraction from and addition to the olefin, and on the orientation of H(D) atom addition, have been studied in the gas phase at room temperature. Effects of isotopic substitution of the olefinic hydrogen atoms on abstraction could not be observed, but abstraction is reduced five-to tenfold by deuteration of the methyl group. Deuteration of either olefinic position enhances the rate of addition to the substituted carbon atom. Disproportionationcombination ratios for deuterium-substituted propyl radicals are not greatly different from those for unsubstituted radicals, the largest effect being for CaDi radicals, for which the overall &/k, is reduced 10-15%.

Orientation of addition of hydrogen atoms to propylene, butene‐1, and isobutene

“…An increase in C3H8/C6Hl4 with increasing light intensity would be consistent with the presence of HgH. This is not observed above -300 torr [37]. More importantly, k 2 / k , is independent of the incident light flux at all pressures studied, which indicates that even if HgH were present, it does not affect the nPr/iPr ratio.…”

“…Since the ratio k z / k l is independent of conversion over a wide range, secondary reactions are not interfering with the relative rate measurement. If (1 + kgd/kgc), using the kd/k, data given by Terry and Futrell [38] which are supported by data recently tabulated [39] for k7d/k7c and k8d/kSc and our measurements using H atom addition techniques [37]. Since the most precise experimental data are for [MP] and [DMB], in general the per cent nonterminal addition was calculated from expression (C) using these data.…”

“…The value for k,/k, (n-butyl, n-butyl) is from a study of the photolysis of 1,l-azo-n-butane by Morganroth and Calvert [41]. Those for 2-butyl, n-butyl and 2-butyl, 2-butyl are from Falconer and Sunder [37]. These are lower kd/k, ratios than are usually quoted for the linear butyl radicals [39], but are close to those for propyl radicals and consistent with the expectation that radicals with very similar structures will exhibit parallel behavior.…”

“…For k d / k , (isobutyl, isobutyl), the value of Slater et al [42] and Terry and Futrell [43] was used. For kd/kc (tert-butyl, tert-butyl), the value recently determined for radicals produced by the addition of H atoms to isobutene [37] was used rather than that determined from the photolysis of 2,2' azoisobutane [43, 441. This significantly higher ratio finds support in the results of Dominguez et al [45], Georgakakos et al [46], and Cvetanovic [47].…”