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Flash-vacuum pyrolysis of azolides of 1,2,4-triazole affords 5-monosubstituted oxazoles.

Tandem mass spectrometry (MS/MS) has been applied to investigate the behaviour of 1-(2-nitrophenyl)benzotriazole [8] upon flash-vacuum pyrolysis (FVP) conditions. Above 500°, 8 is pyrolyzed to give a mixture of 1-nitrocarbazole [11], 1-hydroxycarbazole [12] and carbazole [13] Under similar conditions, 2-(2-nitrophenyl) benzotriazole [9] appears to be more stable; it is however partially isomerized into 8 at high temperatures. Aza analogs of 8, like 1-(2-nitro-4-pyridyl) benzotriazole [10] also loose nitrogen above 500° to give a mixture of 1-nitro-3-azacarbazole [19], 1-hydroxy-3-azacarbazole [16] and 3-azacarbazole [17].

La dihydro-1,4 diphenyl-3,5 pyridazone-4 peut etre obtenue en 2 etapes a partir de chalcone et de diazomethane; la 2nde etape met en jeu le rearrangement de benzoyl-3 phenyl-4 pyrazolines-1 ou -2. Structures a l'aide des spectres de masse MIKE

Mass-analyzed ion kinetic energy spectrometry (MIKE) is shown to be an efficient and rapid method for the analysis of complex sterol mixtures. The method has been applied to the study of the free sterol fractions of five marine and one freshwater invertebrates.

The translational kinetic energy release distribution (KERD) in the halogen loss reaction of the chloro-, bromo-, and iodobenzene cations has been experimentally determined in the microsecond time scale and theoretically analyzed by the maximum entropy method. The KERD is constrained by the square root of the translational energy, i.e., by the momentum gap law. This can be understood in terms of quantum-mechanical resonances controlled by a matrix element involving a localized bound state and a rapidly oscillating continuum wave function, as in the case of a vibrational predissociation process. The energy partitioning between the reaction coordinate and the set of the remaining coordinates is nearly statistical, but not quite: less translational energy is channeled into the reaction coordinate than the statistical estimate. The measured entropy deficiency leads to values of the order of 80% for the fraction of phase space sampled by the pair of fragments with respect to the statistical value. In the case ...

2,5-Dithiacyclopentylideneketene (4) is obtained by flash vacuum pyrolysis (FVP) of the Meldrum's acid derivative 1 and characterized by MS, IR, and NMR spectroscopy. 4 is stable in solution at -50-degrees-C. FVP of 4 as well as the isoxazolone derivatives 2 and 3 results in efficient cleavage into ethylene and ethenedithione, S=C=C=S, which is remarkably stable in the gas phase at high temperature, low pressure, and short contact times but extremely unstable in the condensed state or at higher pressures.

Thionitrosyl cyanide and its radical-cation have been generated for the first time by dissociative ionization of 1,2,5-thiadiazolo [3,4-c](1,2,5)-thiadiazole and characterized by collisional activation (CA) and neutralization-reionization (NR) mass spectrometry. Both neutral and ionized forms are stable species and do not undergo unimolecular rearrangement under the experiment conditions. The NCNS molecule is further characterized by ab initio molecular orbital calculations using various levels of theory up to QCISD(T)/6-311++G(3df,2p) based on MP2/6-311 ++G(d,p) geometries. The stability ordering of the four possible [C, N 2 , S] isomers is (kcal mol −1 ): NCNS 1 (0) > NCSN 2 (14) > CNSN 4 (25) > CNNS 3 (34) > CN + NS (73). The classical energy barrier for the 1,2-migration of the cyano and thionitrosyl groups connecting 1 with 2 and 1 with 3 amount to 80 and 83 kcal mol −1 , respectively, values being larger than the dissociation energy. The geometry and rotational constants of NCNS were predicted using calculations and empirical corrections based on available data on similar molecules; A = 51.986 ± 0.7 GHz, B = 3.521 ± 0.1 GHz, C = 3.298 ± 0.1 GHz. Vibrational wavenumbers of both NCNS and NCSN isomers were computed using QCISD/6-311G(d) wavefunctions. The protonation of thionitrosyl cyanide occurs preferentially at the cyano-nitrogen with a proton affinity PA (NCNS) = 178 ± 3 kcal mol −1 . Several molecular properties of NCNS have also been computed. Mass spectrometric experiments confirm that the product of the reaction NSCl + AgCN → AgCl + [ C , N 2 , S ] is the isomeric thiazyl cyanide (NCSN).

MALDI-MS methodology is nowadays considered as a very reliable technique to determine the chemical structures and the molecular weight distribution of a synthetic polymer. At variance, ESI-MS occupies only a small segment in the analysis of polymers mainly because of the formation of multiple charged ion distributions, which interfere with the molecular distribution in the mass spectra of synthetic polymers. In the present communication, we want to demonstrate that, when applied to fragile polymer samples, both techniques can lead to misinterpretation since in source decomposition of the ionized oligomers can sometimes not be avoided. An accurate knowledge of the source parameters and their influences is therefore a prerequisite prior to start the analysis of the MS data. Moreover, we would like to propose that the best MS methodology to analyze fragile synthetic polymers is to associate the data obtained by both the MALDI-MS and ESI-MS techniques.

Les derives toxiques contenus dans la glande a venin de la fourmi ont un squelette du type perhydro pyrido [1,2-c] pyrrolo [1',2'-a] pyrimidine

Flash-vacuum pyrolysis of azolides of 1,2,4-triazole affords 5-monosubstituted oxazoles.

Les dissociation induites par collisions d'ions [MH-30]+ observes lors de l'ionization chimique (methane) de composes aromatiques nitres indiquent que ces ions sont formes par reduction suivie de protonation et non par perte de NO⋅ des ions moleculaires protones. The collision induced dissociations of [MH – 30]+ ions observed in the chemical ionization (methane) mass spectra of some nitro aromatic compounds show that these ions are formed by reduction in the ion source with subsequent protonation and not by the previously reported losses of NO· from the protonated molecular ions.

Les dissociations induites par collisions d'ions moleculaires crees par impact d'electrons et par echange de charges dans une source d'ionisation chimique (methane) sont compares. Collision induced dissociations of some molecular ions generated by electron impact or charge exchange from methane plasma are compared.

Comparison of collision-induced dissociation–mass analysed ion kinetic energy (CID–MIKE) spectra of cations found by chemical ionisation ethylation with those of chemical ionisation protonation of fixed ethyl derivatives, allows identification of predominant tautomers in vapour phase equilibria.

A real-time analysis of the flash-vacuum pyrolysis products of 1-vinyl-, 1-(2-methylprop-1-enyl)-, and 1-styryl-benzotriazole (3), (16), and (18) has been performed by tandem mass spectrometry. In the 500–700 °C temperature range, these compounds lose nitrogen yielding the N-phenylketenimines (14), (17), and (19), respectively. At higher pyrolysis temperatures (3) gives indole (4)via isomerization of (14), whereas from (16) the secondary products of (17) are benzene and methacrylonitrile. In a preparative pyrolysis of (18) at 800 °C 2- and 3-phenylindole (9) and (10) respectively, have also been detected.