- Substituent Effects on the Decomposition of Bis(tert-butylperoxy)cycloalkanes
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Decompositions of bis(tert-butylperoxy)cycloalkanes have been carried out in cumene and n-alkanes at temperatures of 80-120 deg C and have been compared mainly with the decomposition of tert-alkyl tert-butyl peroxides in order to investigate substituent effects on the homolytic scission of one O-O bond in gem-diperoxides.The decomposition rates of bis(tert-butylperoxy)cycloalkanes are much faster than those of tert-alkyl tert-butyl peroxides; the decomposition rates of the cycloalkanes decrease in the following order: cyclopentane > 3,5,5-trimethylcyclohexane > cyclohexane > cyclooctane > cyclododecane.The effect of ring size on the decomposition and the isokinetic relationships between the activation parameters suggest that stabilization of the transition state by electron donation from the cycloalkyl substituents and repulsion between lone-pair electrons on different peroxy oxygen atoms in the ground state are important factors in the decomposition of gem-diperoxides.
- Matsuyama, Kazuo,Kumura, Hiromi
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- Radical Intermediates in the Thermal Decomposition of 1,1-Bis(t-butyldioxy)cyclohexane
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The thermolysis mechanism of 1,1-bis(t-butyldioxy)cyclohexane (6) has been studied in solutions.The activation parameters obtained in cumene are ΔH=139.5 kJ mol-1 and ΔS=44.8 J K-1 mol-1, and the volatile products are t-butyl alcohol, t-butyl peroxyhexanoate, and 2,3-dimethyl-2,3-diphenylbutane along with minor products of acetone, cyclohexanone, and t-butyl 1-methyl-1-phenylethyl peroxide.The thermolysis of 6 in benzene gave acetone and t-butyl alcohol as major volatile products.The polyester of 2-hydroxyhexanoic acid was obtained both in cumene and benzene as a non-volatile product, and the yield was as high as 76percent in benzene.These facts indicate that oxyl radical (7) undergoes a facile ring-opening reaction yielding 5-(t-butyldioxycarbonyl)pentyl radical (8).The resulting radicals abstract hydrogen atoms either intra- or intermolecularly.The former reaction is predominant in the absence of good hydrogen donors, affording 2-hexanolide and ultimately the corresponding polyesters.
- Sugihara, Yasushi,Watanabe, Yasumasa,Kumura, Hiromi,Nakamura, Tomoyuki,Suyama, Shuji,Sawaki, Yasuhiko
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- REACTIVITY OF CARBOXYLIC ACID ANHYDRIDES IN THE ACYLATION OF TERT-BUTYL HYDROPEROXIDE IN BENZENE
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The kinetics of the acylation of tert-butyl hydroperoxide with carboxylic acid anhydrides (RCO2)O (R = C5H11, CH3, C6H5, CH2Cl) in benzene were studied by GLC from the accumulation of tert-butylperoxy esters.Increase in the electron-withdrawing characteristics of the substituent R in the aliphatic series leads to an increase in the reactivity of the anhydride.The steric effect of the group R does not show up appreciably.The enthalpy and entropy of activation were determined.
- Antonovskii, V. L.,Zhitina, L. V.,Emelin, Yu. D.,Komarova, V. I.
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p. 623 - 626
(2007/10/02)
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