The infrared spectrum of the nitrobenzene anion isolated in solid argon is presented. The nitrobenzene anion was prepared by co-deposition of a nitrobenzene/Ar mixture with high-frequency discharged argon at 4 K. Photosensitive absorptions are assigned to different vibrational modes of the nitrobenzene anion on the basis of isotopic substitutions ((15)N and deuterium), as well as theoretical calculations. The anion loses one electron to give the neutral nitrobenzene upon visible light (500 < lambda < 600 nm) irradiation. Theoretical calculations predicated that the anion has a planar C(2v) symmetry with a shorter C-N bond and longer N-O bonds relative to those of neutral nitrobenzene.

Cocondensation of carbon disulfide with high-frequency discharged argon at 4 K produced carbon monosulfide and atomic sulfur, which reacted spontaneously upon annealing to form the carbon trisulfide molecule as identified from the multiplets observed in mixed (12)C, (13)C and (32)S, (34)S isotopic spectra. On the basis of isotopic substitution and theoretical frequency calculations, infrared absorptions at 1263.3 and 570.1 cm(-1) were assigned to predominantly CS stretching and bending vibrations of CS(3) in solid argon. The CS(3) molecule, which was calculated to have a singlet ground state with C(2v) symmetry, dissociated to form the weakly bound SCS-S complex upon visible light irradiation.

Benzaldehyde was produced from aspartame in aqueous acidic solutions containing ascorbic acid and Cu(II) or Fe(III) ion. Benzaldehyde was identified in the system by GC−MS. The yield of benzaldehyde decreases dramatically as the pH of the medium increases above 2.0. EDTA and DTPA completely inhibited benzaldehyde production, while desferrioxamine inhibited only the Fe(III)-catalyzed reaction. Benzaldehyde is not produced under anaerobic conditions unless H2O2 is added to reaction mixtures. H2O2 is produced by reduction of atmospheric oxygen under aerobic conditions. Benzaldehyde production was dependent on ascorbic acid concentration, but the yield of benzaldehyde decreased as the concentration of ascorbic acid exceeded that of aspartame. Addition of ethanol to the reaction mixture had little or no effect on benzaldehyde production, suggesting a mechanism that may not involve free hydroxyl radical. A mechanism is proposed for the reaction. Keywords: Aspartame; benzaldehyde; ascorbic acid; free radical degradation products; copper(II)

The reaction of chloromethyl radical with molecular oxygen in solid argon has been studied using matrix isolation infrared absorption spectroscopy. The chloromethyl radical was produced via codeposition of chloromethane with high frequency discharged argon atoms. The chloromethyl radical reacted with dioxygen spontaneously on annealing to form the chloromethylperoxy radical, which was characterized on the basis of isotopic splitting (Cl and O) as well as quantum chemical calculations. The chloromethylperoxy radical dissociated to give the weakly bound ClCO-H2O complex under UV light irradiation. The calculations predicted that the ClCO-H2O complex was produced by hydrogen atom transfer from a CHCl(O)-OH intermediate.