REACTION BETWEEN A Q U O FERROUS IONAND CUMENEHYDROPEROXIDE
July, 1956
equilibrium and steady-state approximations, and 1.OO by the equilibrium approximation. Approximations for the Kinetics of Higher Order Reactions.-The degree of success of equation 15 in approximating the exact solution prompts us to look a t higher order reactions where an exact solution has not yet been found and one must resort to an approximation. For the general case nA
zB + kl
k3
C
kz
both the non-rigorous equilibrium and steady-state treatments yield the same form of the rate con-
960
stant as in the previous case whereas our approximation yields’ nkika [AI“ _ -- n2ki [A]”+ kz + ks
dA dt
1
We are currently investigating these higher order reactions as well as studying the implications of these results on the calculation of equilibrium constants from the forward and reverse rate constants of complex reactions. NOTE ADDED riv PRooF.-Equation 15 may be de-
rived in a somewhat different manner than has been used here; see XI. J. Laidler, Can. J . Chem., 33, 1614 (1955). (7) The rate constants refer to production or disappearance of B
THE REACTION BETWEEN AQUO FERROUS IRON AND CUMENE HYDROPEROXIDE’ BY W. L. REYNOLDS~ AND I. M. KOLTHOFF Contribution from the School of Chemistry, University of Minnesota, Minneapolis, Minnesota Received February I , 1068
The rate constants of the reaction between ferrous iron and cumene hydroperoxide have been found to be 3.53 X lo8 exp (-9970/RT) and 9.25 X 108 exp (-10840/RT) liter mole-’ sec-1 in HzO and DzO media, respectively. The main products of the reaction are ferric iron, acetophenone and ethane. A reaction mechanism is postulated and discussed. The possible nature of the rate-determining reaction step is also briefly discussed.
The ability of hydroperoxides to furnish free oxides. Wise and Twigga have investigated the radicals upon reduction with a suitable reducing stoichiometry of the reaction between aquo feragent has led t o their widespread use as initiating rous iron and cumene hydroperoxide (CHP) and agents for p~lymerization.~It has been observed determined some of the products formed. I n this that different hydroperoxides yield widely different report the results of a more thorough study of the rates of polymerization in emulsion polymerization kinetics and mechanism of the latter system me systems. Differences in the rates of polymerization presented. The reaction was also studied in D10 with different hydroperoxides may result from dif- since it was hoped that the results might provide ferences in the rates of reaction of the hydroperox- information about the mechanism of the rate-deterides with a given reductant, from differences in the mining step of the reaction. reactivity of the free radicals produced in the reExperimental duction of the hydroperoxides, and from differences Determination of Rate Constants.-The method by which in the distribution of hydroperoxide between the the reaction between aquo ferrous iron and CHP waB aqueous and organic layers. Since an iron(I1) followed and by which the rate constant was determined species frequently is used as the reducing agent for already has been described.’ When the rate of reaction the hydroperoxide a study of the kinetics of the re- in Dz0 was determined, rate measurements were made in DzO and HzO media to eliminate the possiactions between various hydroperoxides and various alt,ernatively bility that the DqO results were affected by incorrect tunciron(I1) species will provide information whether tioning of the rotated platinum wire electrode. The electhis factor is responsible for the different behavior trolysis cell employed for.DzO media had a capacity of 10 of the hydroperoxides as initiating agents. Kolthoff ml. but otherwise was similar in construction t o the cell used HzO media. The Ih.0 was obtained from Norsk Hydroand Meddial4 Fordham and william^,^ Orr and for electrisk Kvaelstofaktieselskab and was used both without Williamse and Kolthoff and Reynolds’ have re- further treatment and after distillation from alkaline perported results of kinetic studies on rates of reaction manganate and dilute sulfuric acid, similar results being between aquo ferrous iron and various hydroper- obtained with both samples. (1) This work was carried out under the sponsorship of the Federal Facilities Corporation, Office of Synthetic Rubber, in connection with the Synthetic Rubber Program of the United States Government. (2) Abstracted from the theais of W. L. Reynolds presented to the Graduate School of the University of Minnesota in partial fulfillment of the requirernents for the Ph.D. degree, 1955. (3) I. M. I
