Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
A vacuum ultraviolet photolysis of C2H5Br at 147 nm was studied over a pressure range of 0.5-50 torr at 298 K. The effects of additives He and NO were also investigated.The principal reaction products were found to be C2H4 and C2H6, with lesser yields of CH4 and C2H2. With increasing pressure the product quantum yields Φi of C2H4, CH4, and CH2H6 remained constant, while that of C2H2 decreased from 0.03 to almost 0. The effect of He as an additive was found to be extremely small on the quantum yields of the major products. Addition of NO completely suppresses the formation of CH4, C2H2, and C2H6, and reduces partially the production of C2H4. The primary processes appear to involve two electronically excited states. One state mainly yields C2H4 by molecular elimination of HBr and is thought to be due to a Rydberg transition. The other state decomposes to C2H5 and Br radicals by C—Br bond fission. These two competitive reaction modes contribute to the photodecomposition in proportions of 50% and 50%. The extinction coefficient for C2H5Br at 147 nm and at 298 K has been determined as ∊ = (1/PL) In(Io/It) = 712 ± 7 atm-1 · cm-1.
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