PHOTOCHEMISTRY OF BROMOACETYLENE - FORMATION OF HBR AND QUENCHING OF EXCITED BR(42P01/2)

The photolysis of C2HBr has been investigated in the region above 155 nm by the flash photolysis-kinetic spectroscopy technique. Primary processes which involve the formation of both Br(42P03/2) and Br(42P01/2) have been observed. Rate constants for the quenching of excited Br(42P01/2) to ground state Br(42P03/2) by M, where M = He, C2HBr, CF4, and D2, have been determined and found to be equal to 8 ± 3 × 10-16, 3.7 ± 1.6 × 10-12, 1.9 ± 0.5 × 10-13, and 2.8 ± 0.8 × 10-13 cm3 molecule-1 s-1, respectively. HBr has been observed as a secondary product and its rate of formation has been monitored and a mechanism for its formation suggested. The probability of another primary process C2HBr + hv → H + C2Br (6) is discussed. The heats of formation of several C-Br species required for mechanistic considerations are derived. © Copyright, 1979, by the American Chemical Society.