The kinetics of thermolysis of acetyl propinyl peroxide in acetone-d 6 in the temperature range 3233373 K was studied using NMR spectroscopy and the effect of chemically induced nuclear polarization. The peroxide decomposes in acetone at rates comparable with the rates of thermolysis in alcohols, yielding numerous products. In the examined temperature range, the solvent molecules act as efficient donors of deuterium atoms, forming acetylmethyl-d 5 radicals which recombine to a significant extent with the peroxide radicals. A scheme of the processes involved in decomposition of the peroxide was suggested. The parameters of the Arrhenius equation for the peroxide decomposition were determined.Diacyl peroxide are widely used as initiators of polymerization and other free-radical reactions in chemical and petrochemical industries. Therefore, it seems important to analyze the products of decomposition of diacyl peroxides in cheap and available solvents commercially produced in large amounts. One of such solvents is acetone. Data on decomposition of diacyl peroxides in acetone are scarce. Bagdasar'yan and Mulyutinskaya [1, 2] studied only the rate of thermolysis of a 0.185 solution of benzoyl peroxide at 348 K and determined the yields of benzoic acid and carbon dioxide. Leffler et al. studied the effect of methoxy and nitro substituents on the contributions of the radical and nonradical mechanisms in thermolysis of benzoyl peroxide [3] and determined the yield of certain products in decomposition of unstable bis(o-iodophenylacetyl) peroxide [4]. Dutka et al. [5] measured the rates of thermal decomposition of a series of diacyl peroxides and determined the contribution of the induced decomposition to the apparent constant of the process.For aliphatic diacyl peroxides, we found only a single paper [6] in which the product yields in decomposition of acetyl peroxide in a mixture of acetone with carbon tetrachloride were reported.Our goals were to study the effects of chemically induced nuclear polarization, perform kinetic measurements, and analyze, on the basis of the results obtained, the mechanism of thermolysis of one of the simplest unsymmetrical aliphatic diacyl peroxides, acetyl propionyl peroxide I, in acetone-d 6 . Figure 1 shows the 1 H NMR spectrum of a 0.5 M solution of I in the course of thermolysis. Positively polarized are the protons of ethene [d 5.39 ppm, s (4H)], methylene protons of 2-pentanone-d 5 CH 3 CH 2 . CD 2 COCD 3 [1.59 ppm, m (2H)], and methyl protons of butanone-d 5 CH 3 CD 2 COCD 3 [0.98 ppm, quintet (3H)] and propane [0.92 ppm, t (3H)]. Negatively polarized are the methylene protons of ethyl ethanoate [4.10 ppm, q (2H)] and propane [1.39 ppm, m (2H)] and methyl protons of 2-pentanone-d 5 [0.89 ppm, t (3H)] and methanes [0.19 ppm, s (CH 4 ); 0.17 ppm, t (CH 3 D)]. Also, protons of propane and 2-pentanoned 5 have an insignificant contribution of the multiplet 5 4 3 2 1 0 d, ppmFig. 1. 1 H NMR spectrum of a 0.5 M solution of peroxide I in acetone-d 6 at 368 K in the course of thermolysis.
