Hetero-π-systems from 2+2 cycloreversions. Part 1. Gusel'nikov–Flowers route to silenes and origination of the chemistry of doubly bonded silicon

The chemistry of mixed organosulfur-silicon compounds

The product formation channels of ground state carbon atoms, C(3P), reacting with ammonia, NH3, have been investigated using two complementary experiments and electronic structure calculations. Reaction products are detected in a gas flow tube experiment (330 K, 4 Torr) using tunable vacuum-ultraviolet (VUV) photoionization coupled with time of flight mass spectrometry. Temporal profiles of the species formed and photoionization spectra are used to identify primary products of the C + NH3 reaction. In addition, H-atom formation is monitored by VUV laser induced fluorescence (LIF) from room temperature to 50 K in a supersonic gas flow generated by the Laval nozzle technique. Electronic structure calculations are performed to derive intermediates, transition states, and complexes formed along the reaction coordinate. The combination of photoionization and LIF experiments supported by theoretical calculations indicate that in the temperature and pressure range investigated, the H + H2CN production channel represents 100% of the product yield for this reaction. As a result, kinetics measurements of the title reaction down to 50 K and the effect of the new rate constants on interstellar nitrogen hydride abundances using a model of dense interstellar clouds are reported in Paper II.

The c(3p) + nh3 reaction in interstellar chemistry. i. investigation of the product formation channels

Gas phase (298.15 K, 101.325 kPa) adiabatic ionization energies (AIEs) were calculated for 236 organic compounds with the Gaussian-4 (G4) composite method and for 17 molecules at the W1BD level of theory. Functional group types considered span a range of mono- and polyfunctionalized halogenated, saturated and unsaturated, cyclic and acyclic, and heteroatom (N, O, S) substituted moieties without substantial conformational complexity. Excellent agreement was found using both computational methods against available experimental data. Approximately equivalent AIE prediction accuracy was observed between the G4 and the W1BD methods. For compounds with well-constrained experimental AIEs, both levels of theory provide effective chemical accuracy.

Estimated Adiabatic Ionization Energies for Organic Compounds Using the Gaussian-4 (G4) and W1BD Theoretical Methods

The product formation channels of ground state carbon atoms, C(3P), reacting with ammonia, NH3, have been investigated using two complementary experiments and electronic structure calculations. Reaction products are detected in a gas flow tube experiment (330 K, 4 Torr) using tunable VUV photoionization coupled with time of flight mass spectrometry. Temporal profiles of the species formed and photoionization spectra are used to identify primary products of the C + NH3 reaction. In addition, H-atom formation is monitored by VUV laser induced fluorescence from room temperature to 50 K in a supersonic gas flow generated by the Laval nozzle technique. Electronic structure calculations are performed to derive intermediates, transition states and complexes formed along the reaction coordinate. The combination of photoionization and laser induced fluorescence experiments supported by theoretical calculations indicate that in the temperature and pressure range investigated, the H + H2CN production channel represents 100% of the product yield for this reaction. Kinetics measurements of the title reaction down to 50 K and the effect of the new rate constants on interstellar nitrogen hydride abundances using a model of dense interstellar clouds are reported in paper II.

The C(3P) + NH3 reaction in interstellar chemistry: I. Investigation of the product formation channels

Mass spectra of 3,3-dimethyl-3-silathietane and 3,3-diethyl-2,4-dimethyl-3-silathietane. First observation of silathione ions and calculation of their heats of formation

Adiabatic ionization energy of methylenimine

Dissociative ionization of 1,1-dimethyl-1-silacyclobutane, 1,1-bis(trideuteromethyl)-1-silacyclobutane, 1,1,3-trimethyl-1-silacyclobutane, 1,1-bis(trideuteromethyl)-3-methyl-1-silacyclobutane and 1,1,2-trimethyl-1-sila-cyclobutane have been studied. Low energy electron impact fragmentation of 1,1-bis(trideuteromethyl)-3-methyl-1-silacyclobutane results mainly in the loss of ethene with the involvement of the C-methyl group from the rearranged molecular ion. No fragment ions indicating rearrangement of the molecular ion have been detected in mass spectra of 1,1-bis(trideuteromethyl)-1-silacyclobutane. The ionization energies for 1,1,3-trimethyl-1-silacyclobutane, 1,1,2-trimethyl-1-silacyclobutane and 1,1-dimethyl-1-silacyclopentane, and also the appearance energies for the [M − 28]+˙ and [M − 42]+˙ ions, have been measured by photoioniza-tion mass spectrometry. The heats of formation of these ions and of 1,1,3-trimethyl-1-silacyclobutane and 1,1-dimethyl-1-silacyclopentene molecules have been calculated as have the enthalpies of the transformation processes.

Deuterium labelling and thermochemical studies of dissociative ionization of methyl substituted monosilacyclobutanes. Ring expansion in the molecular ion of 1,1,3‐trimethyl‐1‐silacyclobutane

A thermochemical study of dissociative ionization of 4,4-dimethyl-1-thia-4-silacyclohexane and 2,3,3-trimethyl-1-thia-3-silacyclopentane. Decomposition pathways to produce a dimethylsilanethione ion-radical [Me2SiS]+•

N. A. Tarasenko

Papers

Mass spectra of 3,3-dimethyl-3-silathietane and 3,3-diethyl-2,4-dimethyl-3-silathietane. First observation of silathione ions and calculation of their heats of formation

Adiabatic ionization energy of methylenimine

Deuterium labelling and thermochemical studies of dissociative ionization of methyl substituted monosilacyclobutanes. Ring expansion in the molecular ion of 1,1,3‐trimethyl‐1‐silacyclobutane

A thermochemical study of dissociative ionization of 4,4-dimethyl-1-thia-4-silacyclohexane and 2,3,3-trimethyl-1-thia-3-silacyclopentane. Decomposition pathways to produce a dimethylsilanethione ion-radical [Me2SiS]+•