Vibrational spectroscopy of interstellar PAHs: 1-cyanonaphthalene and 2-cyanonaphthalene.

In this work, we present a comprehensive experimental and theoretical study of the vibrational spectra of PAH molecules recently detected in the interstellar medium: 1-cyanonaphthalene and 2-cyanonaphthalene. The room temperature IR spectra of 1- and 2-cyanonaphthalene in the region 100-3100 cm-1 and their vibrational Raman spectra in the region 35-3100 cm-1 are reported here for the first time. A detailed spectral analysis is carried out using quantum chemical calculations employing the DFT methodology. Anharmonic corrections using the VPT2 method yield excellent agreement with the experimental spectra. A re-investigation of the vibrational spectrum of the parent molecule: naphthalene validates the experimental and theoretical methods used. A consistent set of assignments is reported for the fundamental bands of 1- and 2-cyanonapththalene. The experimental and theoretical data presented here would be useful inputs for modelling the role of cyanonaphthalene in astrophysical processes.

Heteroaromatic N-base ligands in 1,10-phenanthroline- and 2,2'-bipyridyl-assisted chromic acid oxidation of (-)-L-sorbose in aqueous micellar acid media: a kinetic study.

In aqueous sulfuric acid media, Cr(VI) oxidation of (-)-L-sorbose in the presence and absence of catalysts like 1,10-phenanthroline (phen), 2,2'-bipyridyl (bipy) have been carried out under the conditions, [(-)-L-sorbose](T)>>[Cr(VI)](T) at different temperatures. Under the experimental conditions, the monomeric species of Cr(VI) has been found kinetically active in the absence of phen and bipy catalysts, while in the heteroaromatic N-base catalysed path, the Cr(VI)-phen and Cr(VI)-bipy complexes have been suggested as the active oxidants. In the catalysed path, Cr(VI)-L complex (L=phen, bipy) receives a nucleophilic attack by the substrate to form a ternary complex which subsequently experiences a redox decomposition through two-electron transfer leading to the organic products and a Cr(IV)-L complex. Both the uncatalysed and catalysed paths show first-order dependence on [(-)-L-sorbose](T) and [Cr(VI)](T). The uncatalysed path shows second-order in [H(+)], while the catalysed path shows a first-order dependence on [H(+)]. The heteroaromatic N-base catalysed path is first-order in [phen](T) or [bipy](T). These findings remain unchanged in the presence of externally added surfactants. The cationic surfactant (i.e., N-cetylpyridinium chloride (CPC)) inhibits the rate in both the catalysed and uncatalysed paths, whereas the anionic surfactant (i.e., sodium dodecyl sulfate (SDS)) shows the rate accelerating effect for both the uncatalysed and catalysed paths. The observed micellar effects have been rationalised by considering the distribution of the reactants between the micellar and aqueous phases in terms of the proposed reaction mechanism.

Oxidation of D-glucose in the presence of 2,2'-bipyridine by CrVI in aqueous micellar media: a kinetic study.

The kinetics of Cr(VI) oxidation of D-glucose to the corresponding lactone in the presence and absence of 2,2'-bipyridine (bipy) has been carried out under the conditions, [D-glucose](T) >> [Cr(VI)](T) at different temperatures in aqueous micellar media. The monomeric Cr(VI) species has been found to be kinetically active in the absence of bipy whereas in the bipy-catalysed path, the Cr(VI)-bipy complex has been found to be the active oxidant. In the bipy-catalysed path, the Cr(VI)-bipy complex undergoes nucleophilic attack by the substrate to form a ternary complex. The ternary complex spontaneously experiences a redox decomposition (through two-electron transfer) in the rate-determining step leading to the product lactone and Cr(IV)-bipy complex. The Cr(IV)-bipy complex then takes part in faster steps in the further oxidation of D-glucose and is ultimately converted into a Cr(III)-bipy complex. In the uncatalysed path, the Cr(VI)-substrate ester experiences acid catalysed redox decomposition (two-electron transfer) in the rate-determining step. The uncatalysed path shows a second order dependence on [H(+)] and a first order dependence on each of the reactants [D-glucose](T) and [Cr(VI)](T). In contrast, the bipy-catalysed path shows a first order dependence on each of the reactants [H(+)], [D-glucose](T) and [Cr(VI)](T). The bipy-catalysed path is first order in [bipy](T). These observations remain unaltered in the presence of externally added surfactants. The effect of the cationic surfactant, N-cetylpyridinium chloride (CPC) and anionic surfactant, sodium dodecyl sulfate (SDS) on both the uncatalysed and bipy-catalysed path has been studied. CPC inhibits both the uncatalysed and bipy-catalysed path, while SDS catalyses these reactions. The observed micellar effects have been explained by considering hydrophobic and electrostatic interactions between the surfactants and reactants.