Consequence of one-electron oxidation and one-electron reduction for aniline

Quantum-chemical calculations were performed for all possible isomers of neutral aniline and its redox forms, and intramolecular proton-transfer (prototropy) accompanied by π-electron delocalization was analyzed. One-electron oxidation (PhNH2 – e → [PhNH2]+•) has no important effect on tautomeric preferences. The enamine tautomer is preferred for oxidized aniline similarly as for the neutral molecule. Dramatical changes take place when proceeding from neutral to reduced aniline. One-electron reduction (PhNH2 + e → [PhNH2]-•) favors the imine tautomer. Independently on the state of oxidation, π- and n-electrons are more delocalized for the enamine than imine tautomers. The change of the tautomeric preferences for reduced aniline may partially explain the origin of the CH tautomers for reduced nucleobases (cytosine, adenine, and guanine)

Resonance-enhanced coherent anti-Stokes Raman scattering in C2

We have obtained resonance-enhanced Coherent Anti-Stokes Raman Scattering (CARS) spectra of the C2 radical formed in a microwave discharge and in an acetylene welding torch. Electronic resonance enhancement was obtained in the Swan system. In order to prepare this work, Swan band emission spectra of C2 had been recorded and assigned using Fourier-transform spectroscopy; this enabled us to determine the optimal conditions for the CARS spectroscopy and to assign the CARS spectra unambiguously. Numerical simulations were performed, with due account for the effects of upper vibrational state populations and for Doppler broadening; the agreement with experimental spectra is fair. We deduce from the spectra C2 densities of about 5 x 1011 cm -3 in the discharge and 1013 cm-3 in the flame. The detection sensitivity is of the order of 1010 cm-3 for our system