The kinetics of a novel method of epoxidation of allyl alcohol (AA) to glycidol (G) with aqueous hydrogen peroxide in the presence of tungstic acid catalyst was studied. The changes in the concentration of glycidol were determined analytically and were found to follow the kinetics of two consecutive pseudo-first order reactions. d[G] /dt = kl [AA] -k0 [GI. The coefficients kl and k2 were calculated by means of the time-ratio method and the effect of several reaction variables on both coefficients was studied. An increase in temperature affects kl to a lesser degree than k2; the respective energies of activation are 15 and 19 kcal. mole-'. Both coefficients are proportional to the concentration of tungstic acid and increase with the decreasing pH of the reaction medium, although not in a uniform fashion. It was concluded that most probably the anion of pertungstic acid, which is produced rapidly from tungstic acid, oxidizes allyl alcohol. The addition of this anion to the double bond appears to be facilitated by the inductive effect of the hydroxy group, or perhaps the protonated hydroxy group, and possibly by the delocalization of the electron pair, with the accompanying negative charge, via the incipient formation of the oxirane-ring. The analogy between this mechanism and the Sx2' substitutions in the allylic systems is pointed out. An alternative mechanism, specific for allylic alcohols and consisting of a rapid esterification of the hydroxy group prior to the attack on the double bond is also considered, The anion of pertungstic acid was found to participate in the opening of the oxirane-ring.(1) Presented a t the 136th American Chemical Society Meeting,( 2 ) M. Mugdan and D. P. Young, J .
KC (M-l) CL 2-04 f . 0.28 2.76 f 0.09 2.22 f 0.09 2-06 & 0-14 1.90 f 0-16 1.78 f 0.16 1-64 f 0.15 590 &-130 620 5 80 900 f 110 1140 f 120 1420 + 140 1690 -f 160 2130 f 180 2 1.56 f 0.15 2320 * 200 0 1.52 f 0.15 2420 f 210 $4 1.50 & 0-15 2420 & 220 e a 1.44 f 0.15 2420 f 240 2 1-35 f 0.18 2400 f 260 a 1.26 f 0.16 2300 f 300 bl, 1-45 f 0.16 1830 f 230 ' 1.49 f 0.16
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