Observation of 13C rearrangement in [13C2]biphenylene formed from benzyne on pyrolysis of [1,6-13C2]phthalic anhydride and [2a,3-13C2]benzocyclobutenedione

1984 ◽  
Vol 37 (8) ◽  
pp. 1643 ◽  
Author(s):  
M Barry ◽  
RFC Brown ◽  
FW Eastwood ◽  
DA Gunawardana ◽  
C Vogel
Keyword(s):  
Mass Spectrometry ◽  
Sulfur Dioxide ◽  
Isotopic Composition ◽  
Gas Phase ◽  
Phthalic Anhydride ◽  
Carbon Skeleton ◽  
Hydrogen Shift ◽  
Thermal Elimination ◽  
A Minor

Examination of [13C2]biphenylene formed by gas phase pyrolysis of doubly labelled benzyne precursors shows that the principal pyrolytic process leads to overall 1,2→1,3 rearrangement of the C6H4 carbon skeleton either in an intermediate C7H4O before decarbonylation or in benzyne itself. A minor process involves an apparent 1,3-hydrogen shift. [1,2-13C2]Ethyne-1,2-diylbistrimethylsilane was acylated with 3-(2,5-dihydro-1,1-dioxothien- 2-yl)propanoyl chloride and the resulting ketone was desilylated to yield 5-(2,5-dihydro-1,l-dioxo-thien-2-yl)[1,2-13C2]pent-1-yn-3-one. Thermal elimination of sulfur dioxide and cyclization followed by dehydrogenation yielded [7,7a-13C2]-2,3-dihydro-1H-inden-1-one which was oxidized and dehydrated to give [3a,4-13C2]isobenzofuran-1,3-dione. This doubly labelled phthalic anhydride was diluted to approximately 5% 13C2 and the resulting material was converted via benzenediazonium- 2-carboxylate into biphenylene at 84�, and pyrolysed at 830� to yield biphenylene, and a sample diluted to 7.5% was converted into [2a,3-13C2]benzocyclobutenedione which was pyrolysed at 650�, 750� and 830� to yield further samples of biphenylene. The biphenylene samples were examined by mass spectrometry at 20 eV to determine their isotopic composition and by 13C n.m.r. spectroscopy to determine the distribution of labelling.

Chemistry of SiO2 Plasma Deposition

1990 ◽  
Vol 204 ◽  
Author(s):  
Donald L. Smith ◽  
Andrew S. Alimonda ◽  
Tzu-Chin Chuang
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Plasma Deposition ◽  
Electron Trapping ◽  
Electrical Characteristics ◽  
Rf Power ◽  
Film Analysis ◽  
Minor Contribution ◽  
Thermal Oxide ◽  
A Minor

ABSTRACTThe chemistry of SiO2 deposition from N20-SiH4 plasma was studied by line-ofsight mass spectrometry coupled with film analysis. If rf power and N2O flow are sufficient, more than enough O atoms are available to convert all of the SiH4 to SiO2, and good electrical characteristics (IV and breakdown) are then obtained with or without He dilution. Gas-phase SimHn(OH)p species make a minor contribution to the deposition and may be the source of the OH in the film. Both [OH] and electron trapping are much larger than for thermal oxide, with or without He dilution.

The thermolysis of ε-halodisilanes: a preference for 1,2-Si Si → O rearrangement or Si—O cleavage over Si=O bond formation

1996 ◽  
Vol 74 (8) ◽  
pp. 1470-1479 ◽  
Author(s):  
Christopher Roos ◽  
Graham A. McGibbon ◽  
Michael A. Brook
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Driving Force ◽  
Bond Formation ◽  
Molecular Ions ◽  
Gas Chromatography Mass Spectrometry ◽  
Major Route ◽  
A Minor ◽  
Group Migration ◽  
Silyl Group Migration

Tris(trimethylsilyl)-2,2,2-trifluoroethoxysilane 6, tris(trimethylsilyl)-2-fluoroethoxysilane 7, and tris(trimethylsilyl)-2-chloroethoxysilane 8 were synthesized and characterized by 1H, 13C and 29Si NMR, IR spectroscopy, and EI and CI mass spectrometry. Thermodynamic considerations would suggest that, as a result of the driving force provided by the formation of a Si—F or Si—CI bond, the thermolyses of these compounds would lead to the formation of bis(trimethylsilyl)silanone 4. To examine this question, gas chromatography–mass spectrometry was as used a detection technique for products resulting from the high-pressure thermolyses of 6–8. The elimination of (Me3Si)3SiCl appears to be the major thermolytic pathway of decomposition for 8 at ambient or higher pressures, although it is accompanied by the formation of other products, some of which could have arisen from the addition of various halosilanes to a silanone. Neither 6 nor 7 thermolyzed cleanly; the former compound was essentially unreactive under the thermolysis temperatures used (850 °C). Of the products produced in the thermolysis of 7, no evidence for the formation of the silanone was obtained. Independently, mass spectrometry was used to study unimolecular reactions of molecular ions derived from 6–8. The major route to solitary ions appears to involve a 1,2-trimethylsilyl migration from Si to O (9 → 10) prior to decomposition, for example, of the m/z 346 parent ion in the decomposition of 6. The preparation of the ionized silanone may be a minor pathway. Some of the other fragmentation pathways for 6–8 are discussed. Key words: gas phase thermolysis, ion rearrangements, silyl group migration, silanone, halosilane.

Transposition des cations radicaux aminés en spectrométrie de masse

1984 ◽  
Vol 62 (5) ◽  
pp. 931-938 ◽  
Author(s):  
Henri Edouard Audier ◽  
Jean Pierre Denhez ◽  
Arielle Milliet ◽  
Georges Sozzi
Keyword(s):  
Mass Spectrometry ◽  
Nitrogen Atom ◽  
Gas Phase ◽  
Internal Energy ◽  
Experimental Results ◽  
Ammonia Molecule ◽  
Hydrogen Shift ◽  
Spectrométrie De Masse ◽  
Good Agreement

It is demonstrated in mass spectrometry that alkylamines substituted at C2 and containing weak internal energy isomerize in the gas phase into intermediary ions composed of ionized cyclopropanes complexed with an ammonia molecule. This process is induced by a C3 hydrogen shift on the nitrogen atom. After opening of the cyclopropane, the dissociation of these complexes leads to m/z 44, 58, and 72 ions having [CH3(CH2)nCH NH2] structures. The mechanism of their formation is demonstrated by the MIKE spectra of 13C and deuterium labelled compounds. The experimental results are in good agreement with those described by Gross etal., who studied the fragmentation of the complexes formed during the reaction between substituted ionized cyclopropanes and ammonia in the gas phase.

Hydrogen-shift isomerism: mass spectrometry of isomeric benzenesulfonate and 2-, 3- and 4-dehydrobenzenesulfonic acid anions in the gas phase

2005 ◽  
Vol 40 (8) ◽  
pp. 1064-1071 ◽  
Author(s):  
Julius Ben-Ari ◽  
Alex Etinger ◽  
Adrian Weisz ◽  
Asher Mandelbaum
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Hydrogen Shift
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