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Kinetics and mechanism of electron transfer to pyridinium chlorochromate (VI) from sulfur containing amino acid, L-cysteine in aqueous and micellar media

Senapati S., Das S., Mohanty P., Patnaik A.K.

Polish Journal of Chemical Technology

2011

Vol. 13, nr 2

6-10

The electron transfer reaction of L-cysteine (RSH) with pyridinium chlorochromate (PCC) has been studied spectrophotometrically over the range 2.0 ≤ 10^3 [RSH] ≤ 6.0; 0.01 ≤ [H+] ≤ 0.2; 298 ≤ T ≤ 318 K and I = 0.3 mol dm-3 (NaClO4). The electron transfer reaction has also been carried out in the presence of anionic, cationic and neutral micelle. The reaction in acid medium is strongly catalyzed by changing [SDS]T (sodium dodecyl sulfate) up to 3 × 10-2 mol dm-3, beyond this concentration of SDS, the rate is retarded. The cationic and neutral micelle has a small effect on the rate. ΔH≠ (kJ mol-1) and ΔS≠ (JK-1 mol-1) values for the k1 and k2 paths are 30.20 ± 0.25, -159.65 ± 0.83 and 29.60 ± 0.62, -127.09 ± 2.17, respectively. The negative activation entropy is indicative of the ordered transition state for the electron transfer reaction. Formation of 2-amino-3-(2-amino-2-carboxy-ethyl) disulfanyl-propanoic acid as product is strongly supported by IR spectra.

Pyridinium chlorochromate oxidation of arsenic(III) in hydrochloric acid

Virkar D.D., Gokavi G.S.

Polish Journal of Chemistry

1998

Vol. 72, nr 10

2267-2271

The reaction between pyridinium chlorochromate and As(III) was studied in hydrochloric acid medium. The reaction was found to be overall second order the added product As(V) was found to decrease the rate. The hydrogen ion was found to catalyse the reaction and it was predicted that both protonated and free pyridinium chlorochromate are active to a different extent. The active species of the reductant was H3AsO3 and the mechanism is discussed in terms of these species. The retardation by the added product is predicted to be due to a competitive ester formation.