ChemInform Abstract: Mass Spectrometry of Triazoles and Their Flash Vacuum Pyrolysis Products.

ChemInform ◽  
1990 ◽  
Vol 21 (33) ◽  
Author(s):  
A. MAQUESTIAU ◽  
F. B. BEN ABDELOUAHAB ◽  
R. FLAMMANG
Keyword(s):  
Mass Spectrometry ◽  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis

Methyleneketenes and methylenecarbenes. VII. Evidence for the pyrolytic generation of methyleneketene (propadienone)

1977 ◽  
Vol 30 (1) ◽  
pp. 179 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
GL McMullen
Keyword(s):  
Mass Spectrometry ◽  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Methylene Chloride ◽  
Liquid Nitrogen Temperature ◽  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Infrared Measurements ◽  
Methanol Vapour

Oxidation of 2,2,5-trimethyl-5-phenylseleno-1,3-dioxan-4,6-dione with m-chloroperbenzoic acid in methylene chloride gives a solution containing 2,2-dimethylspiro[1,3-dioxan-5,2'-oxiran]-4,6-dione and the unstable 2,2-dimethyl-5-methylene-1,3-dioxan-4,6-dione, which forms stable adducts with cyclohexadiene and cyclopentadiene. Flash vacuum pyrolysis of the cyclopentadiene adduct over the temperature range 460- 570° and detection of the components present in the pyrolysate by mass spectrometry showed that cyclopentadiene, acetone, carbon dioxide and methyleneketene (CH2=C=C=O) are formed; the last breaks down into acetylene and carbon monoxide at higher temperatures (520-570°). Infrared measurements on the pyrolysis products kept at liquid nitrogen temperature showed absorption near 2100 cm-1 which is attributed to methyleneketene. Reaction of the pyrolysate with aniline vapour or methanol vapour yielded acrylanilide and methyl acrylate respectively. Pyrolysis in the absence of trapping agents gave a glassy solid on an uncooled glass surface. This solid is considered to be formed by addition of methyleneketene to 2,2-dimethyl-5-methylene-1,3-dioxan-4,6- dione. Methanolysis of the solid and esterification with diazomethane gave dimethyl 2-methoxycarbonyl-4-methylenepentanedioate.

Flash-vacuum pyrolysis of nitroarylbenzotriazoles. A tandem mass spectrometry study

2010 ◽  
Vol 97 (4) ◽  
pp. 245-254 ◽  
Author(s):  
Andre Maquestiau ◽  
Monique Flammang-Barbieux ◽  
Robert Flammang ◽  
Lin-Zhi Chen
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Tandem Mass ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Mass Spectrometry Study

Methyleneketenes and methylenecarbenes. I. Formation of arylmethyleneketenes and alkylideneketenes by pyrolysis of substituted 2,2-Dimethyl-1,3-dioxan-4,6-diones

1974 ◽  
Vol 27 (11) ◽  
pp. 2373 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
KJ Harrington
Keyword(s):  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Infrared Measurements

Flash vacuum pyrolysis (430�) of 5-benzylidene-2,2-dimethyl-1,3-dioxan- 4,6-diones gives benzylidene-ketenes which dimerize to form 2,4- bis(benzylidene)cyclobutane 1,3-diones. Diphenylmethylene-,t- butylmethylene- and isopropylidene-2,2-dimethyl-1,3-dioxan-4,6-diones similarly give the substituted methylene ketenes which dimerize to form 2,4-bis(diphenylmethylene)-, 2,4-bis(t-butylmethylene)- and 2,4- bis(isopropylidene)-cyclobutane-1,3-dione respectively. Infrared measurements on the pyrolysis products kept at liquid nitrogen temperature showed absorption near 2100 cm-1 which was attributed to the methyleneketenes. Reaction of the pyrolysates of ethylidene- and isobutylidene-2,2-dimethyl-1,3-dioxan-4,6-diones with aniline vapour yielded but-3-enanilide and 4-methylpent-3-enanilide respectively.

Alkoxy Isothiocyanates as Intermediates in the Flash Vacuum Pyrolysis of Alkoxythioureas

2009 ◽  
Vol 62 (1) ◽  
pp. 69 ◽  
Author(s):  
Carl Th. Pedersen ◽  
Frank Jensen ◽  
Robert Flammang
Keyword(s):  
Mass Spectrometry ◽  
Ir Spectroscopy ◽  
Reaction Mechanisms ◽  
Theoretical Calculations ◽  
Radical Mechanism ◽  
Tandem Mass ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Free Radical Mechanism ◽  
Initial Cleavage

Methoxy isothiocyanate MeO–NCS 2b was detected by matrix isolation IR spectroscopy following flash vacuum pyrolysis (FVP) of N-methoxythioureas, N-tert-butyl-N′-methoxythiourea 1d being the best precursor. Isothiocyanates 3, amines, and aldehydes are also generated by FVP of several substituted N-alkoxythioureas 1 in the temperature range 400–800°C. The formation of these products can be explained either by secondary pyrolysis of initially formed alkoxy isothiocyanates 2, or by an initial cleavage of the O–N bond in 1 via a free-radical mechanism. N-Cyanoamines 4 and/or the tautomeric carbodiimides 5 are formed by another pathway. The pyrolyses were monitored by IR spectroscopy and online mass spectrometry or tandem mass spectrometry, and the reaction mechanisms are supported by theoretical calculations.

Flash Vacuum Pyrolysis of Some N-Benzylbenzotriazoles and N-Benzylbenzisoxazolones

1998 ◽  
Vol 51 (10) ◽  
pp. 925 ◽  
Author(s):  
Jabbar Khalafy ◽  
Rolf H Prager
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Addition Reactions ◽  
Atom Transfer ◽  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Intramolecular Hydrogen

The flash vacuum pyrolysis products of 2-(benzotriazol-1-ylmethyl)benzonitrile, methyl 2-(benzotriazol-1-ylmethyl)benzoate and the corresponding benzisoxazolones have been characterized. The benzotriazoles lose nitrogen to give diradicals which undergo intramolecular hydrogen-atom transfer or cyclization, while the benzisoxazolones rearrange initially to the corresponding benzaldehyde N-(2-carboxyphenyl)imines which undergo subsequent intramolecular addition reactions.

Thermal and Base-Induced Cyclizations of N-Heteroarylamidinopropanoates

2004 ◽  
Vol 57 (6) ◽  
pp. 577 ◽  
Author(s):  
Adrian Clark ◽  
Rolf H. Prager
Keyword(s):  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis

The potential cyclization of N-heteroarylamidines to annelated pyrimidines by flash vacuum pyrolysis or by treatment with bases has been investigated. The pyrolytic process with the title compounds is complicated by competing formation and rearrangement of an imidoylketene. The major pyrolysis products, the 4-aminopyrimidin-6-ones, were best prepared from the title compounds by reaction with hindered alkoxides, while the pyrolysis byproducts, the 4-alkoxypyrimidin-6-ones, were conveniently prepared from the appropriate isoxazol-5(2H)-one by reaction with the appropriate alkoxide, followed by acidic workup.

A Comparison of the Flash Vacuum Pyrolysis Products of Some N-Acylbenzotriazoles and N-Acylbenzisoxazolones

1999 ◽  
Vol 52 (8) ◽  
pp. 775 ◽  
Author(s):  
Mehdi M. Baradarani ◽  
Jabbar Khalafy ◽  
Rolf H. Prager
Keyword(s):  
Low Temperature ◽  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Radical Processes ◽  
Benzotriazole Derivatives

The flash vacuum pyrolysis (f.v.p.) products of 2-(1H-benzotriazol-1-ylcarbonyl)benzonitrile, methyl 2-(1H-benzotriazol-1-ylcarbonyl)benzoate and 1-(2-chloromethylbenzoyl)-1H-benzotriazole and the cor- responding benzisoxazolones have been characterized. The benzotriazole derivatives gave compounds whose origin suggests the predominance of radical processes. At lower temperatures the benzisoxa- zolones gave benzoxazole products consistent with a singlet carbene intermediate, but which had triplet diradical properties at higher temperatures, leading to the formation of acridine from the chloromethyl compound. The major low-temperature f.v.p. product from the (chloromethylbenzoyl)benzisoxazolone was indolo[1,2-b]benzoxazole.

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