共查询到20条相似文献,搜索用时 0 毫秒
1.
Direct mass spectrometry of polymers. VIII. Primary thermal fragmentation processes in polyurethanes
Salvatore Foti Mario Giuffrida Pietro Maravigna Giorgio Montaudo 《Journal of polymer science. Part A, Polymer chemistry》1983,21(6):1583-1598
The primary fragmentation mechanisms in the thermal decomposition of several polyurethanes were studied by direct pyrolysis into the mass spectrometer. Ester exchange reactions predominate in the primary thermal fragmentation process, causing the formation of cyclic oligomers, which are subsequently cleaved to open-chain oligomers containing hydroxyl end groups. 相似文献
2.
Direct mass spectrometry of polymers. VII. Primary thermal fragmentation processes in polycarbonates
Salvatore Foti Mario Giuffrida Pietro Maravigna Giorgio Montaudo 《Journal of polymer science. Part A, Polymer chemistry》1983,21(6):1567-1581
The primary fragmentation mechanisms in the thermal decomposition of several polycarbonates were studied by direct pyrolysis into the mass spectrometer. Our results indicate that ester exchange reactions predominate in the primary thermal fragmentation process of polycarbonates, causing the formation of cyclic oligomers. 相似文献
3.
Salvatore Foti Mario Giuffrida Pietro Maravigna Giorgio Montaudo 《Journal of polymer science. Part A, Polymer chemistry》1984,22(6):1201-1216
The thermal decomposition of a series of isomeric poly-(oxphthaloyloxyphenylenes) (I–IV) and poly(m-hydroxybenzoic acid) (V) was studied by Direct Pyrolysis–Mass Spectrometry. The results indicate that intramolecular exchange reactions predominate in the primary thermal fragmentation processes, causing the formation of cyclic oligomers which are subsequently cleaved to open-chain fragments. The size and relative abundance of the cycles produced appear to be strongly influenced by steric factors, i.e., by the structure (para or meta) of the repeating unit in each polymer. Remarkably, in the case of poly(m-hydroxybenzoic acid) the formation of cyclic oligomers containing up to seven repeating units is observed. 相似文献
4.
Salvatore Foti Mario Giuffrida Pietro Maravigna Giorgio Montaudo 《Journal of polymer science. Part A, Polymer chemistry》1984,22(6):1217-1229
The thermal decomposition of two series of isomeric aromatic–aliphatic polyesters was studied by direct pyrolysis-mass spectrometry. The results indicate that intramolecular exchange reactions predominate in the primary thermal fragmentation processes to cause the formation of cyclic oligomers. Several secondary thermal processes may occur after the primary step: hydrolytic cleavage of the ester bond, decarboxylation, and β-hydrogen transfer. 相似文献
5.
Anders Hallberg Ibrahim Al-Showaier Arnold R. Martin 《Journal of heterocyclic chemistry》1984,21(3):841-844
Electron impact induced fragmentation patterns of simple phenothiazines have been reinvestigated using metastable ion studies, exact mass measurements and deuterated derivatives. Secondary fragmentation processes involving ions m/e 198, 171, 167, 166, 154, 140 and 139 have been clarified. Mechanisms for the release of sulfur (SH· and CSH·) nitrogen (HCN and H2CN·) containing fragments from phenothiazine molecular ion are proposed based on the deuterium content of the daughter ions obtained from 1,9-dideutenophenothiazine. A revised mechanism for the expulsion of ketene from 10-acetylphenothiazine is suggested based on the fragmentation pattern of the 1,9-dideuterioderivative. The composition of m/e 140 was determined by high resolution measurement to be C10H6N and not C11H7 as previously reported. 相似文献
6.
Jerry Ray Dias 《Journal of mass spectrometry : JMS》1976,11(4):333-346
Mass spectra of various functionalized lanostanes and their deuterated analogs are compared. It is proposed that the transfer of a hydrogen from the 18-methyl group to the 11-oxo group via a McLafferty rearrangement is made geometrically possible by prior ionization of the 13,14 bond which allows an optimum interatomic distance between the oxygen and hydrogen to be acquired; the 8,9 double bond is a requisite for electronic induction of this specific process. Transfer of the hydrogen from the 7β-hydroxy group to position 14 is implicated in the mass spectrum of 3β-acetoxy-7β-hydroxy-5α-lanostan-11-one. 相似文献
7.
A variety of thiol and thion esters, including acetates and benzoates with n-butyl and β-phenethyl alkyl groups, have been studied by electron impact mass spectrometry. Several rearrangement ions were documented and their persistence in low voltage and field ion spectra demonstrated. Among the significant ions found in the rich thion spectra, the most general requires O to S rearrangement of the alkyl group and subsequent cleavage to yield acyl ions (CH3CO or PhCO). This process is more important in longer chain compounds than in the methyl and ethyl homologues studied previously. 相似文献
8.
Leonard K. Dyall 《Journal of mass spectrometry : JMS》1987,22(8):519-522
Fragmentations in the mass spectrum of benzofurazan-1-oxide have been studied using linked scan, accelerating voltage scan and mass-analysed ion kinetic energy spectrometric techniques. Major pathways involve NO·+ NO· and NO·+CO loss, these double losses occurring in such rapid succession as to appear ‘concerted’ in some experiments. Minor pathways are loss of CO2, C2N2O2, or C2HN2O2 from the molecular ion. The major fragment ion, m/z 76, in the conventional mass spectrum is not detected in a mass-analysed ion kinetic energy spectrometric experiment with the molecular ion until collision activation is provided. The conventional electron impact spectrum invariably includes ions from benzofurazan which is produced by thermal deoxygenation in the source. 相似文献
9.
10.
11.
The behaviour of 2-phosphanaphthalene, 3-methyl-phosphanaphthalene and 10-methyl-9-phosphaanthracene upon electron-impact has been compared with that of the carbon and nitrogen analogues. A close resemblance to the fragmentation pattern of the [M ? H]+ ions of 2-methyl-and 2-ethylbenzo[b]thiophene has been observed. It is concluded from the σ40 intensities of the molecular ions, the relatively high intensities of the doubly charged molecular ions and the fragmentation patterns, that these phosphorin derivatives behave as aromatic compounds under electron-impact. From the molecular ion of 2-phosphanaphthalene a remarkable expulsion of a phosphours atom is observed. 相似文献
12.
Jehuda Yinon William C. Brumley George M. Brilis Suryanarayana Bulusu 《Journal of mass spectrometry : JMS》1990,25(1):14-20
A collision-induced dissociation (CID) study of five synthesized nitramines was carried out using a hybrid EBQQ mass spectrometer. CID spectra were obtained in two modes: B/E linked-scan mode and MS/MS mode using the EB sector combination as the first mass spectrometer and the QQ as collision cell and second mass spectrometer, respectively. Fragmentation pathways of the compounds were determined in the electron-impact mode. It was found that dominant fragmentation pathways included the loss of OH, NO2 and HNO2 in addition to the loss of CH2NNO and CH2NNO2. 相似文献
13.
A summary of the mass spectra of metal dithiocarbamate complex salts (ML2 and ML3) is presented. Only divalent metal dithiocarbamate ions without an electronic configuration containing an inert s-orbital electron pair exhibited both expulsion of a ligand radical (L) and the neutral even electron species (L–H) generated from the ligand via hydrogen transfer to the metal-containing fragment ion. Divalent metal dithiocarbamate ions can be generated either by direct electron impact ionization of gas phase ML2 molecules or ionization of ML3 molecules followed by loss of a ligand radical. A highly stable sp2 hybridized, gas phase ion of a monobidentate lead dithiocarbamate complex is proposed. 相似文献
14.
The mass spectral fragmentation pattern of a series of substituted 1,4-benzodioxans is reported. The 2,3-disubstituted compounds show a characteristic fragment peak at mass 121. The 2-monosubstituted compounds do not show this as fragment peak. The mass peak at 121 has been assigned the empirical formula of C7 H5 O2. 相似文献
15.
The mass spectral fragmentation pattern of a series of substituted 1,4-benzoxathians is reported. The di-substituted compounds show a characteristic fragment peak at mass 137. This same fragmentation peak is also present in some of the monosubstituted compounds. In the former case the 137 mass peak is quite intense and is the base peak for some of the di-substituted-1, 4-benzoxathians. The mass peak at 137 has been assigned the empirical formula of C7H5OS. 相似文献
16.
Mass spectral fragmentation pathways were formulated for 1-alkylisatins, 1-alkyl-3-arylimino-2-indolinones and 3-arylimino-2-indolinons bearing no substituent at the 1-position. Deuterium-labelled and 13C-labelled compounds were utilized in this study. An interesting rearrangement of the 1-alkyl compounds, in which the 1-alkyl substituent is incorporated into a fulvene ion, was established. 相似文献
17.
18.
James P. Kutney Guenter Engendorf Tadanou Inaba David L. Dreyer 《Journal of mass spectrometry : JMS》1971,5(3):249-263
A study on the behavior of a large number of monomeric and dimeric coumarins in the mass spectrometer is reported and discussed. The results illustrate that the observed characteristic fragmentation patterns are of considerable utility in the application of mass spectrometry to structure elucidation in this series. 相似文献
19.
The mass spectral and pyrolytic dissociations of o-nitroanisole are reported. The parent ion dissociates by two pathways, principally through loss of CH2O, but a significant fraction through loss of NO. The parent-less-30 peak is therefore a doublet, as shown by high resolution measurements. The thermal decomposition at 600°C and above proceeds also by two pathways, but these are the loss of HNO and HNO2, to form 1,2-methylenedioxybenzene and benzaldehyde respectively. 相似文献
20.
Alberto Ballistreri Domenico Garozzo Mario Giuffrida Pietro Maravigna Giorgio Montaudo 《Journal of polymer science. Part A, Polymer chemistry》1986,24(2):331-346
The thermal fragmentation processes in poly-Schiff bases have been investigated by direct pyrolysis–mass spectrometry. The mass spectral data show that the thermal fragmentation occurring in the polymers under investigation is characterized by hydrogen transfer reactions. In the case of a totally aromatic poly-Schiff base (polymer I ), the thermal fragmentation process involves hydrogen transfer irom the methyne group with formation of fragments bearing nitrile and/or phenyl end groups. In the case of aromatic-aliphatic poly-Schiff bases (polymers II–IV ), the hydrogen transfer process occurs from the aliphatic methylene groups. The latter process involves a lower energy and therefore occurs at lower temperatures with respect to the totally aromatic polymer I , with formation of thermal fragments bearing olefin and/or imine end groups. Beside these fragments, several thermal fragmentation compounds are also evolved by multiple hydrogen transfer reactions. 相似文献