INFRARED SPECTRA OF THE 1-CHLOROMETHYL-1-METHYLALLYL AND 1-CHLOROMETHYL-2-METHYLALLYL RADICALS ISOLATED IN SOLID PARA-HYDROGEN

Abstract

The reaction of chlorine atoms (Cl) with isoprene (2-methyl-1,3-butadiene, C5H8) in solid para-hydrogen (p-H2) matrices at 3.2 K has been studied using infrared (IR) spectroscopy. Mixtures of C5H8 and Cl2 were co-deposited in p-H2 at 3.2 K, followed by irradiation with ultraviolet light at 365 nm to induce the photodissociation of Cl2 and the subsequent reaction of the Cl atoms with C5H8. Upon 365-nm photolysis, a multitude of new lines appeared in the IR spectrum and, based on the secondary photolysis behavior, it was determined that the majority of the new lines belong to two distinct chemical species, designated as set A (intense lines at 1237.9, 807.8, and 605.6/608.2 cm−1, and several other weaker lines) and set B (intense lines at 942.4, 1257.7, 796.7/798.5, 667.9, and 569.7 cm−1, and several other weaker lines). Quantum-chemical calculations were performed at the B3PW91/6-311++G(2d,2p) level for ●C5H7 and the four possible isomers of the ●C5H8Cl radicals, produced from the addition of the Cl atom t...