The mass spectra of trifluoroacetyl-2,5-diketopiperazines. I. cyclo-(-Gly-X), cyclo-(-Ala-X) (X = Gly, Val, Leu, Ile), and cyclo-(-Ala-Ala)

1979 ◽  
Vol 57 (15) ◽  
pp. 2037-2051 ◽  
Author(s):  
George P. Slater ◽  
Lawrence R. Hogge
Keyword(s):  
Mass Spectrum ◽  
Mass Spectra ◽  
High Resolution Data ◽  
Fragmentation Pathways ◽  
Molecular Ion ◽  
Metastable Ions ◽  
Fragmentation Patterns ◽  
The Individual ◽  
Derivatives Of ◽  
Resolution Data

The trifluoroacetyl derivatives of the 2,5-diketopiperazines cyclo-(-Gly-X), cyclo-(-Ala-X) (X = Gly, Val, Leu, Ile), and cyclo-(-Ala-Ala) were examined by GC–MS. The molecular ion was readily detectable only for TFA-cyclo-(-Gly-Gly) (m/e 306, 9%). For those compounds containing a valyl or leucyl/isoleucyl residue the ion of highest mass in the spectrum was formed by elimination of C3H6 or C4H8, respectively, from the molecular ion. In the TFA-cyclo-(-Gly-X) series this ion corresponded to the molecular ion of TFA-cyclo-(Gly-Gly) (m/e 306), and in the TFA-cyclo-(-Ala-X) series, to the molecular ion of TFA-cyclo-(-Ala-Gly) (m/e 320). The fragmentation patterns proposed for these compounds are based on the further degradation of these parent ions so that each compound within a series has a similar mass spectrum. However, sufficient differences were detectable in the various spectra to permit identification of the individual DKP's.Many of the fragmentation pathways devised to explain the mass spectra were supported by high resolution data and appropriate metastable ions.

MASS SPECTRA OF OXYGENATED QUINOLINES

1966 ◽  
Vol 44 (7) ◽  
pp. 781-788 ◽  
Author(s):  
D. M. Clugston ◽  
D. B. MacLean
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Fragmentation Mechanism ◽  
Significant Extent ◽  
Fragmentation Pathways ◽  
Molecular Ion ◽  
One Step ◽  
The Stability ◽  
Hydroxy Compounds ◽  
Fragmentation Patterns

The mass spectra of the monohydroxyquinolines, the monomethoxyquinolines, N-methyl-2-quinolone, and N-methyl-4-quinolone have been recorded. The isomeric hydroxy compounds vary somewhat in the stability of the molecular ion, but all show the same fragmentation mechanism. Two general fragmentation patterns are discernible in the spectrum of each of the monomethoxyquinolines, but there is considerable variation among the isomers in the extent to which the two patterns occur. In addition, 8-methoxyquinoline undergoes a peculiar fragmentation wherein all three methyl hydrogens are lost. The 3-methoxy compound is unusual in that loss of 43 mass units from the molecular ion occurs in one step. Deuterium- and 13C-labelling experiments have proved to be useful in interpreting the fragmentation pathways. The spectra of the two N-methylquinolones prove that O to N methyl rearrangement does not occur to any significant extent upon electron impact.

Mechanism and structure in chemical ionization mass spectrometry: tricyclic flavanoid compounds

1973 ◽  
Vol 26 (7) ◽  
pp. 1577 ◽  
Author(s):  
JW Clark-Lewis ◽  
CN Harwood ◽  
MJ Lacey ◽  
JS Shannon
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Fragmentation Pathways ◽  
Fragment Ions ◽  
Metastable Ions ◽  
Fragmentation Patterns

The chemical ionization mass spectra of a series of tricyclic flavanoid compounds have been examined using isobutane and hydrogen as reagent gases and the fragmen- tation modes have been correlated systematically in terms of structure. The technique produces simple fragmentation patterns and abundant metastable ions. The use of deuterium as reagent gas reveals the influence of extraneous water on the spectra and facilitates the interpretation of the fragmentation pathways. The fragment ions appear to arise from isomeric progenitors protonated at different sites in the molecules.

Fragmentation and rearrangement processes in the mass spectra of perhalogenoaromatic compounds. Part X. Pentafluorophenyl dimethyl derivatives of group V

1976 ◽  
Vol 54 (9) ◽  
pp. 1478-1486 ◽  
Author(s):  
Timothy R. B. Jones ◽  
Jack M. Miller ◽  
J. Lowell Peterson ◽  
Devon W. Meek
Keyword(s):  
Mass Spectra ◽  
Energy Spectra ◽  
Group V ◽  
Fragmentation Pathways ◽  
Transfer Processes ◽  
Metastable Ions ◽  
Ion Kinetic Energy ◽  
Derivatives Of ◽  
Rearrangement Processes ◽  
Resolution Study

A comprehensive low-resolution study of the mass spectra of the compounds C6F5M(CH3)2, where M = N, P, As, is described, fragmentation pathways being assigned with the aid of normal metastable ions and mass analyzed ion kinetic energy spectra (mikes). A comparison of these spectra has re-affirmed the absence of halogen transfer processes for atoms such as N which are incapable of providing the necessary vacant orbitals apparently prerequisite in the mechanisms. The influence of increased coordination to phosphorus and effects on halogen transfer processes are discussed with respect to the mass spectra of the compounds C6F5PX(CH3)2, X = O, S, Se and the gold adducts C6F5P(CH3)2•AuX, X = Cl, Br, I.

The mass spectra of trifluoroacetyl-2,5-diketopiperazines. II. cyclo-(-Val-Val/Leu/Ile), cyclo-(-Leu-Leu/Ile), and cyclo-(-Ile-Ile)

1979 ◽  
Vol 57 (15) ◽  
pp. 2052-2057 ◽  
Author(s):  
George P. Slater ◽  
Lawrence R. Hogge
Keyword(s):  
Mass Spectra ◽  
Molecular Ion ◽  
Alkyl Groups ◽  
Metastable Ions ◽  
Derivatives Of

The trifluoroacetyl derivatives of the 2,5-diketopiperazines cyclo-(-Val-Val/Leu/Ile), cyclo-(-Leu-Leu/Ile), and cyclo-(-Ile-Ile) were examined by GC–MS. The fragmentation of these compounds generally follows the same pathways as previously observed for the TFA-cyclo-(-Gly-X) series (X = Gly, Val, Leu, Ile). However, the spectra can be interpreted on the basis that the molecular ion fragments prior to, or after, one of the alkyl groups is eliminated as olefin. Some ion fragments indicate that both alkyl groups are eliminated but this does not appear to occur directly from the molecular ion. Support for fragmentation of the molecular ion by the suggested route is indicated by a number of isobaric ions although corresponding metastable ions were not observed.The spectra enable the compounds in the series TFA-cyclo-(-Val-X) (X = Val, Leu, Ile) to be readily identified but this is not the case for TFA-cyclo-(-Leu-Leu/Ile) and TFA-cyclo-(-Ile-Ile). However, all of these compounds can be distinguished from TFA-cyclo-(-Gly-X) and TFA-cyclo-(-Ala-X) (X = Gly, Val, Leu, Ile).

Mass Spectrometric Behaviour of (Z)-2-Chloro-3(Dichloromethyl)-4-Oxobutenoic Acid and (Z)-2-Chloro-3(Chloromethyl)-4-Oxobutenoic Acid (Open Forms of MX and CMCF Respectively) Molecular Ions

2002 ◽  
Vol 8 (4) ◽  
pp. 299-303 ◽  
Author(s):  
Rafał Frański ◽  
Przemysław Andrzejewski ◽  
Jacek Nawrocki
Keyword(s):  
High Resolution ◽  
Chlorine Atom ◽  
Molecular Ions ◽  
Mass Spectrometric ◽  
Open Form ◽  
Chloromethyl Group ◽  
High Resolution Data ◽  
Fragmentation Pathways ◽  
Metastable Ions ◽  
Resolution Data

Fragmentation pathways of ( Z)-2-chloro-3(dichloromethyl)-4-oxobutenoic acid (MX open form) and ( Z)-2-chloro- 3(chloromethyl)-4-oxobutenoic acid (CMCF open form) are discussed on the basis of recorded metastable ions and high-resolution data. It was found that the presence of the additional chlorine atom in the chloromethyl group affects the fragmentation pathways of MX. The elimination of the dichloromethyl radical was observed for the MX+• ion but elimination of the chloromethyl radical does not occur for the CMCF+• ion. For the latter compound, elimination of a CO molecule was registered. The elimination of an HCl molecule occurs for both ions.

The isolation of 11-oxotetrahydrorhombifoline from Ormosia coutinhoi and a study of its mass spectrum

1967 ◽  
Vol 45 (7) ◽  
pp. 751-757 ◽  
Author(s):  
Stewart McLean ◽  
A. G. Harrison ◽  
D. G. Murray
Keyword(s):  
Mass Spectrum ◽  
Electron Impact ◽  
Mass Spectra ◽  
Equilibrium Theory ◽  
Side Chain ◽  
Fragmentation Reaction ◽  
Quasi Equilibrium ◽  
Molecular Ion ◽  
Dihydro Derivative ◽  
A Minor

11-Oxotetrahydrorhombifoline (I) has been isolated from the alkaloidal extract of the bark of Ormosia coutinhoi, and its dihydro derivative II has been prepared. An examination of the mass spectra of these compounds and of their 3,3-d2 derivatives has led to the elucidation of the course of the major electron impact induced fragmentations undergone by the molecules. The main fragmentation of I leads to loss of C3H5 from the side chain to form an ion of m/e 221, with a minor path involving a central fission of the molecular ion to form an ion of m/e 150. The mass spectrum of II shows that the loss of C3H7 to form the ion of m/e 221 is a minor process, the main fragmentation reaction involving a central fission to form an ion of m/e 152 analogous to the ion of m/e 150 from I. This change in the spectrum is shown to be consistent with predictions based on the quasi-equilibrium theory of mass spectra.

Spectroscopie de masse des gem-diesters cycliques. Fragment anhydride

1972 ◽  
Vol 50 (10) ◽  
pp. 1535-1538
Author(s):  
Krzysztof Jankowski ◽  
Jean Couturier ◽  
Jean-Yves Daigle
Keyword(s):  
Mass Spectra ◽  
Metastable Ions ◽  
Fragmentation Patterns

Mass spectra of four gem-diesters on three-, four-, five-, and six-member rings are analyzed. The fragmentation patterns of the investigated compounds supported by metastable ions are illustrated by Schemes 1–5 and Tables. A new fragment anhydride is proposed.

Spectres de masse d'hydrazino-2 benzo- et naphtothiazoles et d'hydrazones des méthyl-3 benzo- et naphtothiazolinones-2

1975 ◽  
Vol 53 (23) ◽  
pp. 3677-3680 ◽  
Author(s):  
Jean-Claude Richer ◽  
Philippe Lapointe ◽  
Martine Beljean ◽  
Michel Pays
Keyword(s):  
Mass Spectrum ◽  
Mass Spectra ◽  
Base Peak ◽  
Molecular Ion ◽  
Ion Fragmentation ◽  
Fragment Ions ◽  
Sampling Probe ◽  
Electron Impact Mass ◽  
Impact Mass ◽  
Hydrazone Form

Electron impact mass spectra are reported for the hydrazones of 3-methyl-2-benzothiazolinone (1), of 4-, 5-, 6-, and 7-chloro-3-methylbenzo-2-thiazolinones (2, 3, 4, and 5) and of 3-methyl-naphtho[2,1-d]-2-thiazolinone (6), as well as for 2-hydrazinobenzothiazole (7), for 4-, 5-, 6-, and 7-chloro-2-hydrazinobenzothiazoles (8, 9, 10, and 11) and for 2-hydrazinonaphtho[2,1-d]thiazole (12). The results obtained in the two series are compared. The 2-hydrazone and 3-methyl-benzo-2-thiazolinone and its derivatives all form a base peak corresponding to the molecular ion; fragmentation proceeds mainly by successive losses of·NH2, HCN, HCN, and then CS. Initial losses of N2H2, NH·, and NH3 are minor fragmentation routes.In the case of 2-hydrazinobenzothiazole and its derivatives, the base peak is still that of the molecular ion; however, the relative proportions of the various fragment ions vary with the position of sampling probe inside the apparatus. Thus it is concluded that the observed mass spectrum is that of a mixture of the possible hydrazone-hydrazine tautomers. The principal fragmentations involve the initial loss of NH3 (leading to a stabilized ion), of NH2· (probably from the hydrazone form), and of N2H2.(Journal Translation)

Mass spectra of 4,4-dimethyl-A-homocholestane-3,5- and 3,4a diols and their derivatives

1982 ◽  
Vol 47 (12) ◽  
pp. 3328-3338
Author(s):  
Antonín Trka ◽  
Helena Velgová
Keyword(s):  
Mass Spectrum ◽  
Electron Impact ◽  
Mass Spectra ◽  
Neutral Fragment ◽  
Molecular Ion ◽  
Impact Fragmentation ◽  
Fragmentation Processes

Partial mass spectra of the following 4,4-dimethyl-A-homocholestane derivatives are given: 3,5-epoxides I and II, 3,5-diols III-VI, 3-methoxy-5-ols VII-IX, 3-acetoxy-5-ol X, 3,4a-diols XI-XIV, 3-acetoxy-4a-ols XV-XVIII and 4,4-[2H6]-dimethyl-3,4a-diol XIX, and their electron impact fragmentation investigated. The mass spectra of epoxides I and II, diols III-VI and acetate X are very similar. Considerable differences in mass spectra of methoxy derivatives VII-IX are explained by two mechanisms of elimination of CH3OH from M+. The same similarity of the fragmentation processes and the mass spectra is also observed in diols XI-XIV and acetates XV-XVIII. For the formation of the characteristic ion m/z 288 a fragmentation scheme containing an usual cleavage of the rings A, B, and C is proposed. On the basis of comparison with the mass spectrum of the 4,4-[2H6]dimethyl analogue XIX it was shown that the ion m/z 361 in the mass spectra of diols XI-XIV is formed by elimination of the neutral fragment C6H13 from A-ring of the molecular ion, the last process being accompanied by the 3-hydroxyl transfer from A-ring to the rest of the molecular ion.

Some Aspects of the Mass Spectra of.N-Nitrosamines

1971 ◽  
Vol 49 (9) ◽  
pp. 1367-1371 ◽  
Author(s):  
J. W. ApSimon ◽  
J. D. Cooney
Keyword(s):  
Mass Spectra ◽  
Accurate Mass ◽  
Mass Measurements ◽  
Molecular Ion ◽  
Accurate Mass Measurements ◽  
Characteristic Fragmentation ◽  
Fragmentation Patterns

The mass spectra of seven cyclic N-nitrosamines were examined for characteristic fragmentation patterns. Accurate mass measurements on three of the compounds indicated that the M-17 and M-30 peaks resulted from molecular ion losses of •OH and •NO respectively. The loss of • OH was rationalized in terms of a McLafferty-type rearrangement.

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