Mass spectral characterization of polymers. Primary thermal fragmentation processes in polyureas

The primary fragmentation processes in the thermal decomposition of polymers were studied in detail on a series of structurally related polyureas by direct pyrolysis with a mass spectrometer. Our results indicate that polyureas I–III undergo a quantitative depolycondensation process analogous to that observed for N-monosubstituted polyurethanes. The thermal decomposition of polyureas IV–VI proceeds by intramolecular hydrogen transfer processes that occur at higher temperatures with respect to depolycondensation. Polycarboxypiperazine VI is decomposed by a single-stage decomposition mechanism that leads to fragments with amino end groups and carbon oxide.     

Mass spectral fragmentation of benzofurazan-1-oxide

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.     

Mass spectral fragmentation pattern of 4,4′-bipyridyls. Part I. 4,4′-bipyridyl

The mass spectral fragmentation pattern of 4,4′-bipyridyl is described. The fragmentation proposals which differ from those previously reported are supported by high resolution mass measurements and metastable transitions.     

Mass spectral fragmentation pattern of 2,2′-bipyridyls. Part XII. 2,2′-Selenodipyridine

The mass spectrum of 2,2′-selenodipyridine obtained by electron impact is reported. The base peak in the spectrum is due to the C₅H₄N⁺ ion formed principally by rupture of the central bonds. The molecular ion gives rise to a peak of 50% of the intensity of the base peak. Other fragmentations include loss of H, Se and CSe from the molecular ion and HCN from the M-1 ion.     

Mass spectral fragmentation pattern of 2,2′-bipyridyls Part XI. 2,2′-Iminodipyridine

The base peak in the mass spectrum of 2,2′-iminodipyridine is due to the M-1 ion. There are several minor fragmentation routes from the molecular ion but the principal pathway involves rupture of the central bonds. J. Heterocyclic Chem., 14, 1103 (1977)     

Mass spectral fragmentation pattern of 2,2′-bipyridyls. Part VII 2,2′-dithiodipyridine

The mass spectral fragmentation of 2,2′ -dithiodipyridine involves loss of the elements S, SH and S₂ from the molecular ion in addition to rupture of the central bonds. Molecular rearrangements accompany the disintegration.     

Mass spectral fragmentation pattern of 2,2-bipyridyls. Part V. 2,2′-oxydipyridine

The mass spectrum of 2,2′-oxydipyridine obtained by electron impact is reported. The principal fragmentations involve loss of C₂IIO and CO in addition to rupture of the central bonds. Molecular rearrangements accompany the fragmentations.     

Mass spectral fragmentation patterns of heterocycles. VII . Reinvestigation of fundamental processes in phenothiazines

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.     

Mass spectral fragmentation patterns of heterocycles Part 1. 1,4-Benzodioxans

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.     

Mass spectral fragmentation pattern of 2,2′-Bipyridyls. Part IX. 6-Alkoxy-2,2′-bipyridyls

The mass spectral fragmentation patterns of 6-methoxy-, 6-ethoxy- and 6-propoxy-2,2 ′-bipyridyls are reported. The base peaks in the spectra of both the 6-methoxy and 6-ethoxy compounds are due to the M-lion of 6-methoxy-2,2′-bipyridyl, while the base peak with 6-propoxy-2,2- bipyridyl is due to a species formed by loss of C₃H₆ from the molecular ion.     

Mass spectral fragmentation pattern of 4,4′-bipyridines. Part II. 4,4′-oxybispyridine and 4,4′-thiobispyridine

The mass spectra of 4,4′-oxybispyridine and 4,4′-thiobispyridine are reported. In the former the base peak is due to the molecular ion and the fragmentation routes involve loss of H, CO, HCN, C₂H₂N and C_sHO from the molecular ion as well as rupture of the central bonds. In the latter the base peak is also due to the molecular ion and the fragmentation routes involve loss of H, CS, S, HCN and C₂HS as well as central bond rupture.     

Mass spectral fragmentation pattern of 2,2′-bipyridyls Part IV. Di-2-pyridly ketone

The fragmentation of di-2-pyridyl ketone on electron impact involves elimination of neutral CO from the molecular ion and rearrangement to the 2,2′-l>ipyridyl molecular ion in addition to rupture of the central bonds to form C₅H₄N⁺ and C₆H₄NO⁺ ions.     

Low energy,low temperature mass spectra. 6—A synoptic view

A review is presented of the low energy, low temperature mass spectra of a number of organic compounds, namely alkanes, alkanols, ethers, amines, alkanals, alkanones, alkanoic acids and alkanoic esters. The main fragmentation routes are described and the simplification of the mass spectra as compared with the 70 eV equivalents is emphasized.     

Mass spectral fragmentation of functionalized lanostanes-I

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.     

Mass spectral fragmentation pattern of 2,2′-bipyridyls. Part II. 5-Hydroxy- and 5-alkoxy-2,2′-bipyridyls

The mass spectra of 5-hydroxy-, 5-methoxy-, 5-ethoxy- and 5-propoxy-2,2′-bipyridyls are reported. The fragmentation proposals are supported by high resolution mass measurements and metastable transitions.     

Mass spectral fragmentation pattern of 2,2′-bipyridyls. Part XIII. 6-Chloro- and 6-bromo-2,2′-bipyridyls

The mass spectra of 6-chloro- and 6-bromo-2,2′-bipyridyls are reported. The principal fragmentation route from the molecular ions involves loss of the halogen group to give the M-1 ion of 2,2′-bipyridyl which gives rise to the base peak in the spectra. Loss of HCN before loss of Cl occurs to a small extent with 6-chloro-2,2′-bipyridyl.     

Mass spectral studies of cycloheptatrienes. II—The monochlorocycloheptatrienes

The mass spectra of isomeric chlorocycloheptatrienes have been studied at high and low electron beam energies. Ion kinetic energy spectrometry was utilized to examine the major decomposition pathways. The extreme similarity found in the spectral characteristics of these compounds provides information about the structure of the decomposing molecular ion.     

Mesoionic compounds—XIX: Mass spectral fragmentation patterns for some five-membered systems containing oxygen,nitrogen and sulfur

Mesoionic compounds of the s-triazole, 1,3,4-oxadiazole, 1,3,4-thiadiazole, 1,2,3-thiadiazole, 1,3-thiazole and 1,3-dithiole systems all underwent deep-seated decomposition on electron-impact to small stable ions, determined to a large extent by the nature of the peripheral heteroatoms and the exocyclic substituent. In some instances fragmentation most probably involved an open-chain isomer of the cyclic system.