Chromic acid oxidation of aromatic alcohols

Abstract

The mechanism of the chromic acid oxidation of di-and tri-aryl carbinols has been studied in 80 wt % acetic acid containing sulfuric acid. The reactions are cleanly second-order and give benzophenones in the case of the secondary alcohols and benzophenones plus phenols in the case of the tertiary alcohols. Electron-donating substituents in the tertiary alcohol appear predominantly in the phenol component and the rate-controlling step is believed to be a 1,2-aryl shift. The reaction constant for the migration is pf = -1.44 and that for the overall reaction is pf = -0.879. The presence of manganous ions does not alter these values although it lowers the overall rate of reaction. Although an analogous 1,Zhydride shift mechanism can be written for the oxidation of the secondary alcohols, there are enough points of difference between the oxidations of the secondary and tertiary systems to make this appear unlikely.

Redox Interactions of Cr(VI) and Substituted Phenols: Kinetic Investigation

“…Aqueous Cr(VI) exists as five species in this system: H2Cr04, HCr04~, Cr042-, Cr2072-, and HCr207~. Previous reports have suggested that bichromate, HCrCV, is the primary reactive species (28,29,30,33,34), although this has not been conclusively established for all systems (29,36,42,43). Our experiments with excess Cr(VI) indicate that a monomeric species (H2-Cr04, HCrCV, or Cr042~) is the primary reactant with phenol.…”

Auroral emission from O2(¹Δg)

“…The computed excitation rate for depends mainly on the crqss secti'on at the lowenergy maximum for which there are no measurements at present. It has been suggested [Stewart, 1969] that errors in this type of computation may be large near threshold. Even so, we do not expect the error to approach a factor of 1000; measurements of the total energy loss of electrons in 02 limit the factor to about 1 order of magnitude [Hake and Phelps, 1967].…”

Kinetics and mechanistic approach to the chromic acid oxidation of l-tryptophan with a spectral detection of chromium(III) product

“…Although, chromic acid has been extensively used for oxidation of inorganic [7,8,[11][12][13][14][15] and organic compounds [16][17][18][19][20][21][22][23][24], a little attention has been focused on the oxidation of amino acids by this oxidant [17,24]. This fact may be attributed to the complexity resulting from the existence of various species of chromium(VI) in acidic medium as well as the instability of Cr V and Cr IV oxidation states through the reduction of chromium ion from hexavalent to trivalent state.…”