Oxidation of (CD3)2\dotCX Radicals. I. Reaction of Propane and Isopropyl Radicals with Atomic Oxygen

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Abstract
The reaction of oxygen atoms with propane-1,1,1,3,3,3-d6, (CD3)2CH2, in a fast-flow system was studied with a photoionization mass spectrometer. Isopropyl-d6 radicals, (CD3)2\dotCH, formed by the initial hydrogen abstraction at the 2-position were detected directly. (CD3)2CH2+O(3P)→(CD3)2CH+OH (3) The subsequent reaction of (CD3)2\dotCH radicals with atomic oxygen proceeds by both an deuterium abstraction (61%) and an oxygen addition reaction (39%). The product in the deuterium abstraction was CD2CHCD3 and those in the oxygen addition were (CD3)2CO (18%) and CD3CHO (21%). (Remark: Graphics omitted.) Competition experiments show that (CD3)2\dotCH radicals react (0.029±0.004) times as fast with O2 as with O(3P). In the presence of an excess of O2, CD2CHCD3 was observed in decreased yield (20%) and (CD3)2CO and CD3CHO increased to 32 and 44%, respectively. The rate data for Reaction 3 were fitted by an Arrhenius expression: k 3=(2.0−0.7+1.0)×10−10exp[−(6086±392 cal mol−1)⁄RT] cm3 molecule−1 s−1 (381–627 K). The rate constant of Reaction 3 obtained from the yields of products was 7.9×10−15 cm3 molecule−1 s−1 at 298K.