Infrared absorption of 1-chloro-2-methyl-2-propyl [C-center dot(CH3)(2)CH2Cl] and 2-chloro-2-methylpropyl] [(CH2C)-C-center dot(CH3)(2)Cl] radicals produced in the addition reactions of Cl with isobutene (i-C4H8) in solid para-hydrogen

Abstract

The addition reactions of chlorine atom with isobutene (i-C4H8) in solid para-hydrogen (p-H-2) were investigated with infrared (IR) absorption spectra. When a p-H-2 matrix containing Cl-2 and isobutene was irradiated with ultraviolet light at 365 nm, intense lines in a set at 534.5, 1001.0, 1212.9, 1366.0, 2961.6, and 2934.7 cm(-1), and several weaker others due to the 1-chloro-2-methyl-2-propyl radical, C-center dot(CH3)(2)CH2Cl, and those in a second set including intense ones at 642.7, 799.2, 1098.2, 1371.8, and 3027.3 cm(-1) due to the 2-chloro-2-methylpropyl radical, (CH2C)-C-center dot(CH3)(2)Cl, appeared; the ratio of C-center dot(CH3)(2)CH2Cl to (CH2C)-C-center dot(CH3)(2)Cl was approximately (3 +/- 1):1. The observed wavenumbers and relative intensities agree with the vibrational wavenumbers and IR intensities predicted with the B3PW91/aug-cc-pVTZ method. That the Cl atom adds to both carbons of the C=C bond of isobutene with the terminal site slightly favored is consistent with the energies of products predicted theoretically, but is in contrast to the reaction of Cl + propene in solid p-H-2 in which the addition of Cl to mainly the central C atom was previously reported. The role of the p-H-2 matrix in affecting the reaction paths is discussed. Absorption lines of the complex i-C4H8 center dot Cl-2 and the dichloro-product anti-1,2-dichloro-2-methylpropane, a-CH2ClCCl(CH3)(2), are also characterized. Published by AIP Publishing.