A kinetic study of the reduction of ferrate ion under basic conditions has been completed. The observation that a typical aliphatic ether, tetrahydrofuran, is oxidized at a rate comparable to that of aliphatic alcohols, such as cyclopentanol, indicates that the reaction between ferrate and alcohols is likely initiated by attack of the oxidant at an a-C-H bond, a conclusion that is consistent with the occurrence of primary deuterium kinetic isotope effects (2.8-4.3 at 25°C) when a-hydrogens are replaced by deuterium. Because only acyclic products are obtained from the oxidation of cyclobutanol by ferrate, it may be concluded that free radical intermediates are involved in the reaction. The insensitivity of the reaction rates to substituent effects during the oxidation of substituted mandelic acids indicates that substantial charges are not built up in the transition state. All of these observations are most readily accommodated by a mechanism in which the reaction is initiated by a 2 + 2 addition of an Fe=O bond to the a-C-H of an alcohol to give an organometallic intermediate that subsequently decomposes by homolytic cleavage of the resulting C-Fe bond. Comparisons are made with the reactions between alcohols and other high-valent transition metal oxides. On a rkalisk une ktude cinktique de la reduction de l'ion ferrate dans des conditions basiques. Le fait qu'un ether typique, le tktrahydrofurane, est oxyde a une vitesse comparable B celle des alcools, comme le cyclopentanol, indique que la rkaction entre le ferrate et les alcools est probablement initike par une attaque de l'oxydant sur la liaison a-C-H; cette hypothese est en accord avec le fait que l'on observe un effet isotopique primaire du deuterium (2,8-4,3, a 25°C) lorsqu'on remplace les hydrogenes-a par du deutkrium. En se basant sur le fait que l'on n'obtient que des produits aliphatiques lors de l'oxydation du cyclobutanol par le ferrate suggkre que des interrnkdiaires radicalaires sont impliques dans la reaction. Le fait que les vitesses de reaction d'oxydation d'acides mandkliques substituks ne soient pas sensibles B la nature des substituants indique qu'il n'y aurait pas d'accumulation de charge dans l'ktat de transition. Le meilleur mkcanisme permettant d'expliquer tous ces rksultats implique une reaction initiee par une addition 2+2 d'une liaison Fe=O sur la liaison a-C-H d'un alcool qui conduit a un intermediaire organomktallique que se decompose par la suite par un clivage homolytique de la liaison C-Fe qui en resulte. On a fait des comparaisons avec les rkactions des alcools avec d'autres oxydes de mktaux de transition de valence ClevCe.[Traduit par la rkdaction]

Abstract-The oxidations of organic compounds by permanganate under solvent free conditions have been studied. Thiols and primary aromatic amines undergo oxidative coupling reactions to give disulfides and diazenes, respectively, sulfides are oxidized to sulfones, primary and secondary alcohols are converted to aldehydes and ketones, 1,4-diols and cyclic ethers give lactones and arenes are oxidized to the corresponding a-ketones. The experimental procedure is simple and the products are easily isolated in good yields.

The kinetics of the oxidation of 2-propanol, 1,1,1-trifluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 1-phenyl-2,2,2-trifluoroethanol, 1-(4-methylphenyl)-2,2,2-trifluoroethanol, 1-(3-bromophenyl)-2,2,2-trifluoroethanol, and 1-(3-nitrophenyl)-2,2,2-trifluoroethanol by potassium tetraoxoferrate(VI) have been studied under basic conditions. The products are ketones, formed in almost quantitative yields, iron(III) hydroxide, and dioxygen. The reactions are characterized by substantial enthalpies of activation (40–60 kJ/mol), very unfavorable entropies of activation, large primary deuterium isotope effects, and a positive Hammett ρ value. Both acid and base catalysis are observed. Acid catalysis is attributed to formation of a more reactive oxidant, HFeO4−, at low pH. Base catalysis is attributed partly to the conversion of the reductants to alkoxide ions at high pH, and partly to the reaction of hydroxide ion with tetraoxoferrate(VI) to give a five-coordinated species, HOFeO43−, that reacts rapidly with nucleophiles. A reaction mechanism involving formation of an intermediate ferrate ester is proposed. Keywords: oxidation, alcohols, potassium tetraoxoferrate(VI), ferrate esters, base catalysis, acid catalysis.

A study of the reaction of methyl (£)-cinnamate with quaternary ammonium permanganates in methylene chloride solutions has been completed. The rate of reaction is fastest for those ions which permit the interionic distance in the quaternary ammonium ion pair to be minimized. The Hammett p value for the reaction is 0.95 at 20 °C, and an inverse secondary deuterium isotope effect is observed at the ß-position but not at the «-position. The sign of the p value for this reaction is in direct contrast to the reported value (-0.6) for the oxidation of alkyl vinyl ethers in aqueous dioxane solutions. On the other hand, the fact that the activation parameters for the two reactions are almost identical suggests that the reaction mechanisms cannot be widely divergent. An attempt has been made to visualize a mechanism in which the reactions can proceed through similar intermediates but via either an electron-rich or an electron-deficient transition state depending on the demands of the substituents. The apparent change in mechanism is considered to be simply a reflection of nature's ability to find the lowest energy surface between two points.

The use of permanganate as an effective oxidant in organic chemistry has a long and extensive history. Industrial applications have recently become more attractive environmentally by the introduction of a process for recycling manganese dioxide, a coproduct of these reactions. This recycling approach has reduced the environmental impact of permanganate technology and made it sustainable as defined by the Brundtland Commission. Several current and potential industrial applications of permanganate oxidations are discussed along with a description of some emerging technologies.