Pulse Radiolysis of Neopentane in the Gas Phase.

Abstract

The pulse radiolysis of gaseous neopentane has been investigated in the absence and presence of electron scavengers (SF6, CD3I, CCl4). Deuterium labeling experiments show that the stable product molecules can be accounted for by (a) radical combination reactions involving mainly CH3 and H; (b) hydride ion transfer reactions involving C2H3 +, C2H5 +, and C3H5 +; (c) neutralization reactions of C4H9 + and C5H11 +; and (d) unimolecular dissociation of the parent ion (C5H12 +) and of electronically excited neopentane. Neutralization of the t-C4H9 + ion, which is the major positive ion in the system occurs as follows: (a) t-C4H9 + + e → i-C4H8 + H and (b) t-C4H9 + + e → 2CH3 + C3H6. It is shown that C5H11 + produced in hydride ion transfer reaction C n H m + + neo-C5H12 → C n H m+1 + C5H11 + (where C n H m + = C2H3 +, C2H5 +, and C3H5 +) rearranges to the CH3C+(CH3)CH2CH3 structure prior to neutralization. A detailed accounting of all products produced in the unimolecular and bimolecular reactions led to the conclusion that the ratio of neutral electronically excited molecules to parent ions (Nex/N+) is 0.28.