Oct., 1950
DECOMPOSITION OF CUMENE HYDROPEROXIDE BY FERROUS IRON
weighed. The amount of polymercuration so determined was added to that found by the carrier technique.
Acknowledgments.-The authors gratefully acknowledge the Fellowship granted to one of us (W. K.) by the Atomic Energy Commission, and the help and cooperation of Dr. Gerhart Groetzinger of the Institute for Nuclear Studies, who bombarded the sodium bromate solution from which some of the needed BrE2was obtained. Summary 1. Both toluene and nitrobenzene were mercurated (a) with mercuric acetate, and (b) with mercuric perchlorate in perchloric acid solution.
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2. The amounts of ortho and para and of meta isomers thus formed were determined in each case. The analytical method for the tolyl mercuric salts depended upon converting these compounds to bromotoluenes, and analyzing these by a tracer technique requiring BP2. 3. It was found that mercuration with mercuric perchlorate in perchloric acid solution gave the pronounced orientation effects typical of electrophilic substitution ; mercuration with unionized mercuric acetate showed much less strongly marked orientation effects. CHICAGO, ILLISOIS
RECEIVED MARCH18, 1950
~CVNTRIHUTION FROM THE RESEARCH AND DEVELOPMENT DIV.,POLYXER CORPORATION LTD.]
The Decomposition of Cumene Hydroperoxide by Ferrous Iron in the Presence of Oxygen' BY J . W. L. FORDHAMAND H. LEVERNE WILLIAMS In most low temperature free radical initiated action. Baxendale, Evans and Park4 in a study emulsion polymerization recipes the initiating of the analogous reaction between hydrogen free radicals are formed by the reaction between peroxide and ferrous iron found that the rate of the reaction is given by k = 1.78 cumene hydroperoxide (CHP, C B H ~ C ( C H ~ ) ~ O.Oconstant H) and complexed ferrous iron. In order to obtain x 10ge-lOJ'JO/~* 1. mole-' set.-'. Stoichiometric Ratios.-Pub1ications4a5s6 indiinformation on the rate of production of these free radicals under various conditions a study of cate that in dilute aqueous solutions of hydrogen the decomposition of C H P was undertaken. In a peroxide and ferrous iron the ratio of ferrous previous publication2 it was shown that in the iron oxidized to peroxide consumed in an acidic vicinity of 100' the decomposition of CHP in a medium is two to one whether the reaction takes styrene solution may be described by two simul- place in the absence or presence of oxygen. This taneous reactions, a unimolecular fission pre- fact supports the mechanism proposed for dilute sumably a t the 0-0 bond producing two radicals solutions of low PHI4i.e. sec.-l). per molecule (k = 2.7 X 1012e-ao,400/Rr F e + + + HOzH +F e + + + + OH- + HO. and a radical induced decomposition having no F e + + + HO. +F e + + + + OHeffect on the number of radicals in the sysHowever, in the CHP-ferrous iron reaction tem (k = 1.00 x 105e-6t500/RT1. mole-' sec.-l). The present paper deals with the decomposition under similar conditions, the ratio is approxiof CHP in an acidic dilute aqueous solution mately one to one in the absence of oxygen and a t lower temperatures in the presence of ferrous varies from slightly less than two to more than iron and oxygen with particular emphasis on the four to one depending upon the initial concenrate constant of the primary radical producing tration of CHP and ferrous iron in the presence ~ authors have also found the reaction and as an intermediate step to the study of ~ x y g e n . The of the decomposition in alkaline medium in the ratios are considerably greater than two to one in presence of complexed iron. The study was the presence of oxygen. The stoichiometry of carried out in the presence of oxygen rather than the reaction in an alkaline medium could not be its absence because of the experimental dif- investigated in the presence of oxygen because of ficulty of removing completely from very dilute the rapid oxidation of ferrous iron in the absence solutions the effect of oxygen traces. Very of hydroperoxide. The results are in Tables I and little has been reported on this although Kolt- 11. From these results it is evident that at a pH hoff and Medalias obtained an approximate value of 27 1. mole-' set.-' at 2 i 0 for the rate from 1 to 4 an increase in the initial ratio of constant of the primary radical producing re- ferrous iron to CHP, a decrease in the pH of the solution, or a decrease in the initial CHP con(1) Presented a t the Detroit Meeting, Division of Physical and Inorganic Chemistry, American Chemical Society, April, 1950. (2) J. W. I.. Fordham and H. L. Williams, Can. J . Krsearch, 17B,
!I43 (1949). (8) I. hI. KolthoR' ;nid A . I. Medalia, THISJ U I I H X A L , 71, 3789 (194Y).
(4) J. H. Baxendale, .Soc.. 41, 1.55 (1946).
M. G. Evans and G S.Park. l'rnns. F a r a d a y
( 5 ) I. M. Kolthoff and A. I. hledalia, 'l'iiis Jur nh.ii.. 71, 3 7 7 7
(lY49). (6) I. M. Kolthoff and A. 1. Medalia, ibid , 71, 3784 ( 1 9 4 9 ) ,
1. W. L. FORDHAM AND H. LEVERNEWILLIAMS
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'rABLt I REACTIONk4TIOS OF CHP WITH Fe" AT 25.10"
IS 0 1
Vol. 72
N HtSO4
ICHPIo, IM Xi08
lite l+lo/[CHPjo
Rdho
2 oo 8.00 2 00
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4 011 5 [JU 5 ju 4 00 i o ntb .j 60 Residual CHP present instead of residual Fe TABLE
KEACTIOX RATIOS OF
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4.00 4.no
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