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The kinetics of the gas phase bond isomerization of allyl fluoride, allyl chloride and allyl bromide, catalyzed by HBr and ultraviolet light, has been studied in the temperature range of 150-250' and at pressures of 3.5 to 50 mm. The reactions are very clean, first order in allyl halide and HBr, and have a light intensity exponent of unity. A quantum yield for allyl chloride of 3200 indicates a chain reaction. Dilution with inert gases is almost without effect, indicating that excited state intermediates are not involved. A small wall effect is observed. The evidence indicates a free radical reaction, involving hydrogen abstractions by bromine atoms, with replacement at the other end of the allylic radical.

The kinetics, stoichiometries, and mechanisms of the following oxidations of acetoin (3-hydroxy-2butanone) to biacetyl(2,3-butanedione) have been investigated : (1) the Fe(II1)-catalyzed oxidation by 02, (2) the Fe(II1)-catalyzed oxidation by H202, and (3) oxidation by Fe(II1) under anaerobic conditions. In addition, approximate rate constants for the acid-catalyzed enolizations of acetoin have been determined. At 25 O, ionic strength ca. 0.2 M, and pH 1.5-2.3, the rate of 0 2 uptake in reaction 1 follows the expression: rate = (9.1 X 10-7 se~-1)[Fe(III)][acetoin]/[H+], and 2 mol of acetoin reacts with 1 mol of O2 to give 2 mol of biacetyl. Under comparable conditions reaction 2 proceeds faster than reaction 1 and can occur by two different mechanisms, one (2a) which involves Fe(I1) as an intermediate, and another (2b) in which Fe(I1) is not an intermediate. In both cases 1 mol of acetoin reacts with 1 mol of H2O2 to give 1 mol of biacetyl. At 25O, ionic strength ca. 0.2 M and pH 1.6-2.1 the disappearance of H202 in reaction 2b follows the expression: rate = (2.5 X lop3 A4-

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