Insights into the Photodecomposition of Azidomethyl Methyl Sulfide: A S/S Conical Intersection on Nitrene Potential Energy Surfaces Leading to the Formation of -Methyl--sulfenylmethanimine.

UV photodecomposition of azidomethyl methyl sulfide (AMMS) yields a transient -methylthiaziridine which rapidly evolves to -methyl--sulfenylmethanimine at 10 K. This species was detected by infrared matrix isolation spectroscopy. The mechanism of the photoreaction of AMMS has been investigated by a combined approach, using low-temperature matrix isolation FTIR spectroscopy in conjunction with two theoretical methods, namely, complete active space self-consistent field and multiconfigurational second-order perturbation.

Reaction of iminopropadienones with amines--formation of zwitterionic intermediates, ketenes, and ketenimines.

Five aryliminopropadienones 4a- d have been synthesized by flash vacuum thermolysis (FVT) by using two different precursors in each case. These compounds were deposited at 50 K at a pressure of ca. 10(-6) mbar together with three different nucleophiles, namely, trimethylamine (TMA), dimethylamine (DMA), and diethylamine (DEA), in order to study their reactions as neat solids during warm-up by FTIR spectroscopy.

Reaction of iminopropadienones with amines: mechanistic explanations of zwitterionic intermediate, ketene and ketenimine formation.

The complex reaction of thermally generated iminopropadienones with amines in the gas phase and upon matrix deposition and its varying product composition is investigated using density functional theory. In the high energy gas phase addition a single amine molecule reacts readily with iminopropadienone with the decisive step being a 1,3-hydrogen shift and activation barriers of at least 100 kJ/mol. In accordance with the experiment, the formation of ketenes is favored.

Formation of neutral methylcarbamic acid (CH3NHCOOH) and methylammonium methylcarbamate [CH3NH3+][CH3NHCO2-] at low temperature.

We study low temperature reactivity of methylamine (CH3NH2) and carbon dioxide (CO2) mixed within different ratios, using FTIR spectroscopy and mass spectrometry. We report experimental evidence that the methylammonium methylcarbamate [CH3NH3(+)][C3NHCO2(-)] and methylcarbamic acid (CH3NHCOOH) are formed when the initial mixture CH3NH2:CO2 is warmed up to temperatures above 40 K. An excess of CH3NH2 favors the carbamate formation while an excess of CO2 leads to a mixture of both methylammonium methylcarbamate and methylcarbamic acid.

Photochemical dehydration of acetamide in a cryogenic matrix.

Vacuum ultraviolet (VUV) irradiation of acetamide has been monitored by Fourier transform infrared spectroscopy in argon matrix at 10 K. Several primary photoproducts, including HNCO ratio CH(4) and CO ratio CH(3)NH(2) molecular complexes, and acetimidic acid, which is reported for the first time, were characterized. The acetimidic acid identification was based on comparison between the experimental and theoretical (B3LYP) infrared spectra.

Vacuum ultraviolet (VUV) photodecomposition of urea isolated in cryogenic matrix: first detection of isourea.

Vacuum ultraviolet (VUV) irradiation at wavelengths of lambda > 160 nm of urea-h4 (NH2CONH2) and urea-d4 (ND2COND2) has been monitored by Fourier transform infrared spectroscopy in argon and xenon matrixes. Several primary photoproducts, such as HNCO:NH3 (isocyanic acid:ammonia), CO:N2H4 (carbon monoxide:hydrazine) molecular complexes, and isourea (H2N(OH)C=NH), which is reported for the first time, were characterized. The assignment of complexes was achieved by co-depositing the pairs of respective species, whereas the isourea identification was based on the comparison between the experimental and theoretical (B3LYP) infrared spectra.

Carbodiimide production from cyanamide by UV irradiation and thermal reaction on amorphous water ice.

Cyanamide (NH(2)CN), an interstellar molecule, is a relevant molecule in prebiotic chemistry, because it can be converted into urea in liquid water. Carbodiimide (HNCNH), the most stable cyanamide isomer, is able to assemble amino acids into peptides. In this work, using FTIR spectroscopy, we show that carbodiimide can be formed from cyanamide at low temperature (10 K), by a photochemical process in argon matrix, in water matrix, or in solid film.

Matrix isolation Fourier transform infrared study of photodecomposition of formimidic acid.

The UV isomerization of formamide (HCONH2) trapped in xenon, nitrogen, argon, and neon cryogenic matrices has been monitored by Fourier transform infrared (FT-IR) spectroscopy. Formamide monomer is the only species present in the matrices after deposition; when UV-selective irradiation was carried out at 240 nm, the n --> pi transition allowed us to observe the formation of several isomers of formimidic acid [H(OH)C=NH]. On these latter species, we carried out selective IR irradiation of their OH stretching mode and compared the experimental and theoretical (B3LYP/6-311+G(2d,2p)) sets of bands.

Experimental study of water-ice catalyzed thermal isomerization of cyanamide into carbodiimide: implication for prebiotic chemistry.

Cyanamide (NH2CN) is a molecule of interstellar interest which can be implied in prebiotic chemistry. We showed, by FTIR spectroscopy, that cyanamide can be isomerized in carbodiimide (HNCNH), another interstellar relevant molecule, by a reaction involving the amorphous water-ice surface as catalyst. This isomerization occurs at low temperature (T < 100 K) which agrees quite well with that expected in the interstellar clouds composed of dust grains in which water is the most predominant constituent.