The reductions of n-butyl, sec-butyl, and tert-butyl hydroperoxides by triphenylphosphine in ethanol have been shown to follow second-order kinetics with k2's equal, respectively to 107.2e−8.4/RT, 109.0e−10.8/RT, 108.8e−11.2/RT. Similar results obtain in CH2Cl2, but in hexane the rate equation requires an additional term, k3[Ph3P][RO2H]2, though the overall reaction is somewhat faster than in the other solvents.Retardation, apparently by adventitious impurities, has been observed in some cases, but attempts to inhibit the reaction by free radical traps were unsuccessful. Parallels with reduction of hydroperoxides by organic sulfides suggest a similar non-radical mechanism.
The reaction of hydroperoxides with triphenylphosphine is catalyzed by the addition of strong acid. Likewise in hydroxylic solvents, the log of the bimolecular rate constant increases linearly with the solvents' autoprotolysis constants. Soluble salts of molybdenum or vanadium are lo4 to lo5 times more effective catalysts than H + . The reaction shows promise as a method for quantitative comparison of the effectiveness of these compounds in augmenting the electrophilic character of hydroperoxides.On observe que la reaction entre les hydroperoxydes et la triphtnylphosphine est catalyske par les acides forts. I1 en est de mCme dans les solvants hydroxyliques ou le log de la constante de vitesse bimolkulaire augmente d'une facon lintaire avec les constantes d'autoprotolyse des solvants. Les sels solubles de molybdene ou de vanadium sont des catalyseurs de 10" a lo5 fois plus efficaces que H + . I1 semble que cette reaction pourrait eventuellement Ctre utiliste pour determiner d'une facon quantitative l'efficacitk de ces composes pour augmenter le caractere electrophile des hydroperoxydes.
R. H I A~, CHRISTINE MCCOLEMAN, and G. R. HOWE. Can. J. Chem. 53,559 (1975). Triphenylstibine reduced r-Bu02H to r-BuOH almost as fast as Ph3P does, while triphenylarsine reacts only 1/60as fast. Both reductions are first-order ineach component; in ethanol k, for Ph3Sb and Ph3As are 106.7e-9.71RT and 109.1e-15.7RT; respectively. The reductions are not very sensitive to choice of solvent, but are strongly catalyzed by compounds of molybdenum and vanadium.The relative rate order PH3P 3 Ph3Sb > Ph3As is ascribed to two conflicting trends,availability of d-orbitals for T-bonding with peroxidic oxygen, and the Group VB to oxygen bond strength.R. HIATT, CHRISTINE MCCOLEMAN et G. R. HOWE. Can. J. Chem. 53,559 (1975). La triphenylstibine rkduit le r-Bu02H en r-BuOH presqu'aussi rapidement que le fait Ph3P; par ailleurs la triphenylarsine rtagif environ 60 fois moins rapidement. Chacune des reductions est du premier ordre en chacun des rkactifs; dans I'ethanol, les valeurs de k, pour Ph3Sb et Ph3As sont respectivement de 106.7e-9.71RT et l@.le-l5.7/RT. Les reductions ne sont pas sensibles a u choix du solvant mais sont fortement catalysees pardes composis du molybdkne et du vanadium.L'ordre relatif des vitesses Ph3P 3 Ph3Sb >Ph3As est attribue h deux tendances contradictoires soit la disponibilite d'orbitales pour former des liens T avec I'oxygkne du peroxyde et l a force de la liaison de I'oxygkne avec les eltments du groupe VB.[Traduit par le journal]
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