Spectral Evidence for the One-Step Three-Electron Oxidation of Phenylsufinylacetic Acid and Oxalic Acid by Cr(VI)

Abstract

The co-oxidation of a mixture of phenylsulfinylacetic acid (PSAA) and oxalic acid (OxH 2 ) by Cr(VI) in 20% acetonitrile-80% water (v/v) medium follows third order kinetics, first order, each with respect to PSAA, OxH 2 and Cr(VI). The reaction involves nucleophilic attack of sulfur atom of PSAA on chromium of the oxidizing species, Cr(VI)-OxH 2 to form a ternary complex, Cr(VI)-OxH 2 -PSAA followed by a one-step three-electron reduction of Cr(VI) to Cr(III) and simultaneous oxidation of both the substrates. The reaction is catalysed by Mn 2+ ion while retarded by Al 3+ ion. Electron releasing substituents in the meta-and para-positions of the phenyl ring of PSAA enhance the rate of co-oxidation while electron withdrawing substituents retards the reaction. The Hammett plots at different temperatures exhibit excellent correlation with negative ρ values. The reaction series obey isokinetic relationship and the observed isokinetic temperature is lying below the experimental range of temperature.

Optical Properties of the Synthesized Cr2S3 Nanoparticles Embedded in Polyvinyl Alcohol

“…The intensity of these bands increases with increasing salt concentration providing evidence for the incorporation of the Cr 2 S 3 into PVA matrix. The observed blue shift of the two bands comparing to the Cr(III) spectra (421 and 592) nm in reference (Subramaniam, et al 2013), attribute to the quantum confinement effect (Seoudi, et al 2012), Whereas the shift in onset of absorption spectra towards the higher wavelength upon increasing Cr 2 S 3 confirm the increase of the average size of nanoparticles (Deshmukh, et al 2012). The optical absorption coefficient α is defined as the ability of a material to absorb light of a given wavelength; it provides the most valuable optical information such as the electronic band structure and the optical energy band gap for material identification.…”

Hydrothermal biosynthesis of chromium sulphide nanoparticles using egg yolk and its catalytic activity in degradation of dyes

“…The peaks at 1165 cm −1 in samples calcinated at 400°C and 1138 cm −1 in those heated at 1000°C signify C-O stretching vibrations which may be attributed due to the high amount of biomolecules contributed by the egg yolk. The peaks at 1659 cm −1 in 400°C calcination samples and 1638 cm −1 in 1000°C calcination samples represent C=O stretching vibrations which represent the amide-I signals of the proteins present in the egg yolk which get coated upon the nanoparticles during synthesis [35]. The peak at 2353 cm −1 from the samples at 400°C corresponds to O-H and N-H stretching vibration which then disappear in samples calcinated at 1000°C.…”

“…The peak at 2926 cm −1 from the samples at 1000°C which is not present at 400°C corresponds to O-H stretching vibration as well as intramolecular hydrogen bonding resulting in stabilization of the so formed nanoparticles. The peaks at 3279 cm −1 in 400°C calcination samples and 3242 cm −1 in 1000°C calcination samples represent N-H stretching in resonance with amide-II overtone contributed by the proteins from the egg yolk [35].…”

Kinetic and mechanistic features of the thiolactic acid oxidation by chromium(vi) in acidic environment

“…As shown in Figure 8, the behavior predicted by equation (17) was obtained. Equation 17 (20) Intercept=…”

“…The condensation complex formed (  3 X C r O ) further decomposes by transfer of electrons, this being often the rate determining step. Depending on the nature of the reducing agent and the molecularity of this electron transfer step, the number of electrons changed may vary from one [14,15] (to form Cr(V)) to two [16][17][18] (yielding Cr(IV)) or even three in some co-oxidations [19,20]. The involvement of the intermediate valence states Cr(V) and Cr(IV), both also oxidizing agents, as well as that of other very reactive intermediates, such as organic radicals, brings about complicated reaction schemes [6].…”