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.

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.

Volatile Products From Pyrolysis of Cotton Fabrics Finished With Thps-Urea-Phosphate

1983 ◽  
Vol 1 (3) ◽  
pp. 165-176 ◽  
Author(s):  
William E. Franklin
Keyword(s):  
Mass Spectrometry ◽  
Carbon Dioxide ◽  
Flame Retardant ◽  
Cotton Fabrics ◽  
Pyrolysis Mass Spectrometry ◽  
Mole Percent ◽  
Pyrolysis Products ◽  
Urea Phosphate ◽  
Volatile Products ◽  
Water Fractions

Volatile products evolved during the pyrolysis of cotton fabrics treated with various add-ons of THPS-urea-phosphate flame retardant were measured by pyrolysis-mass spectrometry. Molar fractions of nine primary, volatile pyrolysis products were determined, accounting for 82-89 mole percent of the products. Three classes of volatile products were distinguished on the basis of the response of the product fractions to add-on of the flame retardant. Increasing add-on decreased the anhydroglucose fractions. Small add-ons increased the "furan" fractions and large add-ons decreased them. Nonfuel fractions increased with increasing add-on. Inverse relations were found between anhydroglucose fractions and water fractions and between "furan" fractions and carbon dioxide fractions. The flame retardancy of the cotton fabrics had the best correlation with the water fractions. These results are compared and contrasted with data from the pyrolysis of cotton fabrics treated with another flame retardant, THPOH-ammonia.

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

scholarly journals Carbon Implanted in Optical Grade Fused Silica: Annealing Effects in Reducing and Oxidizing Atmospheres

1996 ◽  
Vol 438 ◽  
Author(s):  
Y. S. Tung ◽  
R. Mu ◽  
A. Ueda ◽  
D. O. Henderson ◽  
P. W. Wang ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Infrared Spectroscopy ◽  
Fused Silica ◽  
Infrared Measurements ◽  
Annealing Effects

AbstractCarbon is implanted into fused silica with doses of 1, 3, 6, 10×1016 ions/cm2. Infrared spectroscopy has identified the formation of CO and CO2 molecules in the implanted glasses. The relationships among concentrations of carbon dioxide, carbon monoxide and carbon doses are established by the infrared measurements. Annealing under different atmospheres have dramatic effects on CO and CO2 concentrations.

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.

scholarly journals Cave Air Analysis with Gas Chromatography Mass Spectrometry

2021 ◽  
Author(s):  
Gyula Nyerges ◽  
Dénes Szieberth ◽  
Judit Mátyási ◽  
József Balla
Keyword(s):  
Mass Spectrometry ◽  
Carbon Dioxide ◽  
Gas Chromatography ◽  
Carbon Monoxide ◽  
Stationary Phase ◽  
Gas Analysis ◽  
Gas Chromatography Mass Spectrometry ◽  
Cave System ◽  
Validation Parameters

Gas chromatography (GC) is a frequently used analytical method for the determination of permanent and organic air components. The analysis usually needs two different columns in practice. The molecular sieve stationary phase can separate oxygen, nitrogen and carbon monoxide, but irreversibly adsorbs carbon dioxide and water. Porapak type columns are applicable for the measurement of carbon dioxide, however oxygen, argon, nitrogen and carbon monoxide are co-eluted. Usually these two types of columns are used in parallel for the determination. Carboxen stationary phase can separate carbon monoxide and carbon dioxide, but argon, oxygen and nitrogen are co-eluted. Thermal conductivity detector (TCD) and flame ionization detector (FID) are used commonly together for the determination of the separated components. TCD is applied for permanent gas analysis whereas FID – combined with a methanizer – is used for the detection of carbon monoxide, carbon dioxide and light hydrocarbons. Mass spectrometer (MS) is also a potential detector, because the properly chosen fragment ions can increase the selectivity.We developed a method for the determination of air components, using only one column and one detector. This method is suitable for the measurements by combining the advantages of the carboxen column with mass spectrometry. The validation parameters of the method were in the acceptable interval, so this method is able to determine the air components. The application of this technique to the analysis of cave air provided valuable information to the exploration of the Molnár János cave system.

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.

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