Thermolysis-mass spectrometry

There are two basic approaches to direct mass-spectral analysis of volatile additives, namely constant-temperature heating and temperature-programmed heating (sometimes called thermolysis-mass spectrometry,... 

Thermolysis-mass spectrometry is ideal for examining the amount of residual monomer and processing solvents present in polymers. In thermolysis, the polymer is heated from room temperature to 200-300 °C, and is then often held isothermally in order to drive off volatile components. Low-temperature pyrolysis (350-400 °C) of PP compounds in direct mass-spectral analysis has shown volatiles from PP at every carbon number to masses well above 1000 Da [37]. 

The major fragmentation in mass spectra of 1,2,5-oxadiazoles is attributed to the loss of nitrile and nitrile oxide or expulsion of NO. The conversion of 3,4-dicyano-l,2,5-oxadiazole-2-oxide (3,4-dicyanofuroxan) 10 to cyanogen iV-oxide 11 (Equation 5) was investigated under the conditions of collisional activation (CA) and neutralization-reionization (NR) mass spectrometry. Flash vacuum thermolysis mass-spectrometry (FVT-MS) and flash vacuum thermolysis infra-red (FVT-IR) investigations of furoxans 10, 12, and 13 reveal that small amounts of cyano isocyanate accompany the formation of the main thermolysis product 11 <2000J(P2)473>. 

Mass spectrometry was applied in conjunction with thermolysis studies leading mainly to sulfines and rearranged products with four-membered sulfoxides and to a loss of sulfur dioxide with sulfones The fragmentation pattern of thietes under electron impact can be explained by the sequential loss of the elements of sulfur monoxide and oxygen from an intervening cyclic sulfmate intermediate . ... 

The thermolysis of a variety of 1,2,4-trioxanes in methanol has been followed by mass spectrometry and provided evidence of the corresponding products. A smdy of the thermal decomposition of 3,6-diphenyl-1,2,4,5-tetroxane in toluene and methanol revealed a significant solvent effect that supported a homolytic stepwise mechanism instead of a concerted process. ... 

As part of a mechanistic and synthetic study of nucleophihc carbenes the spirocyclic 4(5/l)-oxazolone 18 has been obtained from benzoyl isocyanate (Scheme 6.1) Thermal extrusion of nitrogen from the 1,3,4-oxadiazoline 14 produced the carbonyl ylide 15 that fragmented via loss of acetone to the aminooxycarbene 16. Spectroscopic data [gas chromatography-mass spectrometry (GC-MS), infrared (IR), proton and C-13 nuclear magnetic resonance ( H and NMR)] of the crude thermolysate was consistent with 18. The formation of 18 was rationalized to result from nucleophihc addition of 16 to benzoyl isocyanate followed by cyclization of the dipolar intermediate 17. Thermolysis of 19 and 21 under similar reaction conditions afforded 20 and 22 respectively, also identified spectroscopically as the major products in the thermolysate. 

The cyclization of allyl silyl amine 697 by hydrosilylation led to silaazetidine 698, which was subjected to flash vacuum thermolysis at 700-900°C at 10-4 hPa313. The silanimines 699 and 700 themselves were too reactive to be observed by high resolution mass spectrometry of the reaction mixture, but their cyclic dimers, the cyclodisilazane 701 and 702 and a trapping product with t-BuOH 703, were definitely confirmed... 

Under the conditions of mass spectrometry, the salts are converted into radicals (Section 4.31.1.4). Radicals (18) and anions (32) are also obtained by irradiation in a solvent, which provides the reductant (72TL5213). 3,5-Diphenyl-l,2-dithiolylium-4-olate (33) produces tetraphenyl-p-benzoquinone on thermolysis (78AJC297), presumably by dimerization and loss of sulfur. 

The previous discussion has referred to photolysis and thermolysis only. Many of the transformations described have also been observed on mass spectrometry of isoxazoles, although it is not always clear whether they occur as a result of electron impact or by prior thermal reaction.211-212 It should be noted that such reactions can create problems in the use of mass spectrometry for elucidating the structures of isoxazoles. 

Other attempts have been made to use mass spectrometry as a basis for predicting thermolysis products. It has been observed that the product of pyrolysis (38) of the cyclic sulphite (37) corresponded to twice the molecular formula of one of the peaks C5H40+ in the mass... 

Since a large number of polycarbonates possessing the desired structural features can be prepared from a variety of diols, it is useful to develop simple methods to predict their behavior as resist materials. To this effect, we have devised spectroscopic methods to follow the degradation of the polycarbonates under a variety of thermolysis or acidolysis conditions. For example, the thermolysis of the solid polymers can be followed conveniently by gas-chromato-graphy-mass spectrometry. The thermolysis is a very clean reaction which proceeds as shown in Scheme III without side-product formation. Figure 4 shows the gas chromatographic trace obtained when polymer II is subjected to thermolysis near 250 the products analyzed by the mass spectrometer have the expected structures as shown in Figure 4. 

I. K. Igumenov, Investigation of Thermolysis Mechanism of Gas Phase of Ni(II) Chelates by Mass Spectrometry, International Symposium on Chemical Vapor Deposition, CVD-XIV and EUROCVD 11, The Electrochemical Society Proceeding, Vol.97, (No.25), 1997, pp.89-96. 

Flash-vacuum thermolysis of thietane 1-oxide affords the reactive intermediate, sulfine, CH2=S=0. Field-ionization mass spectrometry of the thermolysis products also indicates the formation of thietane, propenal, ethylene, CaHsO, CaHg, and hydrogen sulfide. A 1,2-oxathiolane intermediate was suggested. The exo sulfoxide 118 is thermally stable, but the endo derivative 115 decomposes around 200°C, probably because of the ease of -elimination ... 

Mass spectrometry is an analytical method of choice for identification of volatile compounds and has been employed in investigation of thermolysis and acidolysis mechanisms of chemical amplification resists [96, 121, 122]. This technique has been also utilized in screening of resists systems, especially Si-containing 193 nm bilayer resists,for outgassing [438,439]. MALDI-TOF mass spectroscopy has been applied to characterization of dendritic resist polymers. 

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