Silver (III) oxidation of the DL-mandelate ion

Abstract

The oxidation of DL-mandeiate (MAN-) by [Ag(OH),]-in strongly alkaline media has been investigated by stopped-flow spectrophotometry. Product analysis shows that benzaldehyde is the sole organic product when MAN-is in excess. The rate law is kobs = where a = (6.2 f 0.2) dm3 mo1-l s-l and b = (7.0 f 0.3) dm6 mol-2 s-' at 25 "C and I = 1.3 mol dms. Oxidation of benzaldehyde (to benzoic acid) by Ag"' is more than an order of magnitude slower than the mandelate reaction. Activation parameters for both hydroxide-dependent and -independent paths are AH: = (59.3 f 2.1) kJ mol-', A$ = (-32.0 0.5) J mol-' K-' and AH: = (48.0 & 2.3) kJ mol-', AS: = (-68.50.6) J mol-' K-l, respectively. Two different mechanistic pathways are discussed. A base-catalysed process, followed by C-C cleavage, seems to be the most probable mode of decarboxylation. The comparative non-reactivity of phenylglyoximate and amethoxyphenylacetate ions underlines the importance of the a-OH group in the mandelate oxidation.

Silver-Catalyzed Decarboxylative Fluorination of Aliphatic Carboxylic Acids in Aqueous Solution

“…The Ag(II)- or Ag(III)-mediated decarboxylation of carboxylic acids is well-documented. , It is reasonable to assume that Ag(III)–F has a reactivity similar to that of Ag(II) in decarboxylation since the Ag–F bonding is substantially covalent in Ag(III) and Ag(II) fluorides . While the fluorine atom transfer from Ag(II)–F to an alkyl radical is unprecedented, transition-metal-assisted halogen (Cl or Br) atom transfer, that is, trapping of an alkyl radical by a complexed metal halide in a higher oxidation state (M n +1 L m X) to give the alkyl halide and the metal ion in a lower oxidation state (M n L m ), is well-known .…”

Improved Synthesis of Fluticasone Propionate

“…The Ag(II)- or Ag(III)-mediated decarboxylation of carboxylic acids is well-documented . According to the literature, a tentative mechanism of the decarboxylative fluorination with AgNO 3 /Selectfluor was proposed.…”

Mechanism of the oxidation of hydrazoic acid by tetrachloroaurate(III) ion

“…Such coordination has been proposed in the oxidations of hypophosphate [42], iodide [43] and mandelate [44] by the square planar Ag(OH) 4 -complex. The formation of a similar axial intermediate complex has been proposed in the oxidation of histidine [20], SO 3 2-ion [45] and oxalic acid [18] by AuCl 4 -ion.…”