The Thermal Decomposition of Cumene Hydroperoxide in Relation to Certain Aspects of Emulsion Copolymerization

Abstract

Cumene hydroperoxide decomposes near 100 °C. in reactive solvents but only slightly in stable solvents. The decomposition is not a simple first order reaction. The results may be interpreted as the sum of a first and a three-halves order reaction. Approximate over-all energies of activation of the decomposition determined from the data obtained for the decomposition in cumene (31 kcal. per mole), methanol (31 kcal. per mole), styrene (20 kcal. per mole), and the energy of activation for the initial unimolecular step in benzene–styrene mixtures (30.4 kcal. per mole) agree with the values reported for similar peroxides and hydroperoxides in similar solvents. The energy of activation for the radical-induced decomposition is 6.5 kcal. per mole. The data suggest that the first step of the decomposition is the unimolecular reaction involving scission of the O–O bond. If the resultant C6H5C(CH3)2O∙ radical is not reactive towards the solvent, it tends to lose either a phenyl or a methyl radical and form acetone or acetophenone respectively. The former reaction predominates. The decomposition rapidly becomes autocatalytic, particularly in cumene at higher temperatures, presumably because of the radical-induced decomposition of the hydroperoxide. The identified products of decomposition in cumene can be explained by the various reactions of the radicals formed in the mixture. The polymerization shortstop 2,5-ditertiarybutylhydroquinone reacts rapidly below 0 °C. with an equimolar weight of cumene hydroperoxide, and the resulting products retard further thermal decomposition at 90 °C. quite strongly. The shortstop 2,4-dinitrochlorobenzene does not react with cumene hydroperoxide and would seem to act merely as a powerful retarder for the decomposition at the higher temperature. The effect of other related compounds on the decomposition of cumene hydroperoxide in styrene was less marked and agrees with the relatively less effectiveness of these compounds as stoppers in emulsion copolymerization.

The Role of Peroxides in the Liquid-Phase Oxidation of Hydrocarbons

“…The pre-exponential factor in the expression for the rate constant, obtained directly from the kinetic curves for the breakdown of hydroperoxides at high initial concentrations, was much smaller than that expected for a truly unimolecular process. Thus, the proposal that there is an induced peroxide breakdown can be used to explain the form of the relationship between the rate of decomposition and the concentra tion of hydroperoxide obtained in a number of cases, for example in the breakdown of cumene hydroperoxide in cumene [21] : This again confirms that the rate constants obtained in this manner are the effective rate constants for some complex process.…”

“…5). The complexity of the kinetic rules, found in the decomposition of hydroperoxides, is explained by the majority of authors [20][21][22][23] on the basis that free radicals, produced by the unimolecular rupture of the O-O bond, induce a chain process of hydroperoxide decomposition which is superimposed on the unimolecular breakdown. Thus, the expressions below were obtained for the decomposition of tetralyl hydroperoxide in tetralin: k = 0-93 X 10 9 Q-2U00RT s e c -i [ 1 9 ] k = 2-2 x 10 9 e -2 4 4 0 0 i r r sec" 1 [20] and we obtained [13] k = 2 -2 x l 0 9 e -2 4 4 0 0 i r r s e c -1 for the decomposition of decyl hydroperoxide in partially oxidized decane.…”

La/Zn Bimetallic Oxide Catalyst for Epoxidation of Styrene by Cumene Hydroperoxide: Kinetics and Reaction Engineering Aspects

“…On the other hand, the dissociation energy of the peroxy bond in CHP is more in the mother compound cumene (∼31 kcal/mol) than in styrene (∼20 kcal/mol). 15 Furthermore, thermal decomposition of CHP happens even under ambient environment wherein, it dissociates into numerous products such as cumyl alcohol, acetophenone (ACP), and alpha methylstyrene (AMS) via a free radical mechanism. Styrene polymerization and thermal decomposition of CHP have been reported to be induced by identical free radicals.…”

“…CHP has been reported to be used as initiator for styrene polymerization in earlier works. On the other hand, the dissociation energy of the peroxy bond in CHP is more in the mother compound cumene (∼31 kcal/mol) than in styrene (∼20 kcal/mol) . Furthermore, thermal decomposition of CHP happens even under ambient environment wherein, it dissociates into numerous products such as cumyl alcohol, acetophenone (ACP), and alpha methylstyrene (AMS) via a free radical mechanism.…”

The Role of Alpha-Ketols in the Low-Sugar Redox Recipe for Low Temperature Emulsion Copolymerization

“…(35) showed that a water solublc l~eroxide such as hydrogen peroxide disappeared from the ~nedium prior t o polymerization. Ho~~rever, the work published by Fordham and Williams (5,6,7,8,9), by Icharasch et al (22,23) and by I<olthoff et al (24,28,30) str-ongly suggested that the most probable locus of initial free radical fornlation was in the aqueous phase.…”