Quinolinium chlorochromate oxidation

The kinetics of the oxidation of a series of para- and meto-substituted benzaldehydes by quinolinium chlorochromate are first order in substrate, oxidant, and hydronium ion the results were subjected to a Taft analysis. Oxidation of 2-pyridinecarboxaldehyde to the acid by dichromate follows an unusual mixed fourth-order rate law it is first order in hydronium ion and Cr(VI), and second order in aldehyde. 

Quinolinium dichromate (QDC) oxidations of primary and secondary alcohols both proceed via a cyclic chromate ester. Acrylonitrile polymerization was observed in the oxidation of several para- and meffl-substituted benzaldehydes to the corresponding benzoic acids by quinolinium chlorochromate (QCC). QCC oxidations of diphenacyl sulfide and of aromatic anils have been studied. 

From the temperature dependence of the substantial kinetic isotope effect (KIE) observed in the oxidation of diols to hydroxycarbonyl compounds by 2,2/-bipyridinium chlorochromate (BPCC), it is proposed that hydride transfer occurs in a chromate ester intermediate, involving a six-electron Hiickel-type transition state.9 A similar conclusion is drawn for the oxidation of substituted benzyl alcohols by quinolinium chlorochromate.10... 

Oxidation of several primary aliphatic alcohols with potassium dichromate, pyri-dinium dichromate, quinolinium dichromate (QDC), imidazolium dichromate, nico-tinium dichromate, isonicotinium dichromate, pyridinium fluorochromate (PFC), quinolinium fluorochromate, imidazolium fluorochromate, pyridinium chlorochromate (PCC), quinolinium chlorochromate (QCC), and pyridinium bromochromate (PBC), in aqueous acetic acid and in the presence of perchloric acid, showed similar kinetics. The values of the reaction constants did not differ significantly, indicating operation of a common mechanism.1... 

In a brief communication, it was reported that quinolinium chlorochromate is a selective oxidant for primary alcohols for example, this reagent is reported to oxidize the diol (11) selectively to the aldehyde (12 equation 12). 

A relatively large number of oxidation studies have featured 3-benzyl-5-(2-hydroxyethyl)-4-methyl-l,3-thiazolium chlorochromate (BCC), benzyltriethy-lammonium chlorochromate (BTEACC), imido zolium chlorochromate (ICC), 1-methylimidazolium chlorochromate (MCC), morpholinium chlorochromate (MPCC), piperidinium chlorchromate (PPCC), pyridinium chlorochromate (PCC), quinald inium chlorochromate (QnCC), quinolinium chlorochromate (QLCC), tetraethylammonium chlorochromate (TEACC), and tetrakis(pyridine) cobalt(II) chromate (TPCC). 

The oxidation of aliphatic primary and cyclic alcohols " to the corresponding aldehydes and ketones by quinolinium chlorochromate (QCC) is first order each in QCC, alcohol, and H+ a mechanism involving rate-limiting hydride ion transfer has been proposed. The relative reactivity for the cyclic alcohols (cyclohexanol < cyclopen-tanol < cycloheptanol < cyclooctanol) is explained on the basis of I-strain theory. The oxidation of mandelic, lactic, and glycolic acids by QCC is first order with respect to oxidant and H+ and fractional order with respect to substrate. ... 

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