- Sulfoquinovose and its aldonic acid: Their preparation and oxidation to 2-sulfoacetaldehyde by periodate
-
6-Deoxy-6-C-sulfo-D-glucopyranose (sulfoquinovose) has been prepared and characterised as its brucinium and potassium salts. The bis- cyclohexylammonium salt of its aldonic acid, 6-deoxy-6-C-sulfo-D-gluconic acid, has also been obtained. Their oxidation by sodium periodate gives 2- sulfoacetaldehyde.
- Roy, Alexander B.,Hewlins, Michael J.E.
-
-
Read Online
- Kinetics and mechanism of aliphatic amine oxidation by aqueous (batho)2CuII
-
The kinetics of oxidation of a large series of aliphatic amines by the "high-potential" oxidant (batho)2CuII (batho = 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolinedisulfonate) was studied under pseudo-first-order conditions (excess amine) in water or in 30% aqueous methanol (v/v) at 25 °C over the pH range 7-11. The oxidations follow bell-shaped pH-rate profiles, with the low-pH leg reflecting the fact that only the free amine base is subject to oxidation and the high-pH leg representing conversion of (batho)2CuII to an ineffective oxidant at high pH. The latter is thought to be (batho)CuII(OH2)OH on the basis of the observed effect of [batho] on rate at high pH, and curve fitting of the rate data yielded estimates of the unitless Keq values governing this conversion. The variation in rate with degree of N-substitution and other structure-reactivity trends (such as the effect of ring size and the non-rate-retarding effect of 2,4,6-trimethyl substitution on PhCH2NR2) support a mechanism involving initial outer-sphere one-electron transfer, followed by proton transfer to the solvent, and then a rapid second one-electron oxidation to give imine/iminium product. Inner-sphere coordination of chelating amines shuts down the redox reaction, presumably as a consequence of displacement of the batho ligand(s) needed for high oxidant strength. Deuterium kinetic isotope effect (DKIE) measurements (i) comparing PhCD2N(CD3)2 vs PhCH2N(CH3)2 (intermolecular DKIE) and (ii) determining N-dealkylation preference in the case of PhCH2N(CH3)CD2Ph (intramolecular DKIE) suggest that the initial electron transfer is mainly rate-limiting. A rate comparison between erythro and threo diastereomers of 1,2-diphenyl-2-piperidinoethanol indicates a stereoelectronic preference for one-electron oxidation at nitrogen when held antiperiplanar to a β-hydroxyl. Stoichiometry studies using an excess of the Cu(II) oxidant reveal regioselective and chemoselective factors governing the overall amine-to-iminium oxidations.
- Wang, Fengjiang,Sayre, Lawrence M.
-
p. 248 - 255
(2007/10/02)
-
- KINETICS OF OXIDATIVE DECARBOXYLATION OF L-CYSTEINE BY PERMANGANATE
-
Oxidative decarboxylation of L-cysteine by permanganate in sulfuric acid medium has been found to be first order in both oxidant and substrate concentrations.Various hypotheses for the mechanism of acid catalysis have been tested.The energy and entropy of activation have been calculated as 52.7 and 56.5 kJ mol-1 and -101.7 and -94.9 J mol-1 K-1 for two stages of the reaction, respectively.A mechanism is proposed, which is in agreement with the experimental data.
- Ameta, S. C.,Gupta, H. L.,Pande, P. N.,Chowdhry, H. C.
-
-