The rates of enolization of cyclohexanone have been determined at 145 and 172 °C in D2O and with buffers. The rates of oxidation were evaluated at temperatures of 145, 172, and 193.5 °C with oxygen partial pressures of 20.4 to 131 atm. The rate of enolization was 10–160 times faster than the rate of oxidation thereby supporting the previously proposed concept of enol intermediacy for the oxidation of ketones. The oxidation was first order in cyclohexanone and 1/2 order in oxygen. The rate of oxidation was increased by the addition of traditional phenolic inhibitors. The products isolated were formic, acetic, butanedioic, pentanedioic, hexanedioic, and 5-oxohexanoic acids. The activation parameters were calculated to be ΔH≠, 22 kcal/mol; ΔS≠, −27 eu, log A, 7.6 for the oxidation and ΔH≠, 12 kcal/mol; ΔS≠, −42.3 eu, log A, 4.13 for the enolization. Based on these observations a mechanism has been postulated whereby an oxygen molecule forms a transitory adduct with two enolates of cyclohexanone. The latter may then split by a reversible reaction to form an intermediate which may then isomerize or oxidize to either 2-hydroxycyclohexanone or 1,3-cyclohexanedione. Upon further oxidation the former yields hexanedioic acid. The latter then undergoes a reverse condensation in the aqueous media to 5-oxohexanoic acid which upon further oxidation yields formic plus pentanedioic acid and acetic plus butanedioic acid.
Preparation and Characterization of Graphene Oxide – Attapulgite composite and its use in kinetic study of Alizarin Dye Adsorption from Aqueous Media