Spectrometrie de Masse de Produits Naturels Aromatiques Polychlores

Mass spectra of three natural aromatic compounds are reported: 1,4-dimethoxy-2,3,5,6-tetrachlorobenzene (I), 4-methoxy-2,3,5,6-tetrachlorophenol (II) and 1,4-dimethoxy-2-nitro-3,5,6-trichlorobenzene (III). Main fragmentations are explained according to the formation of a quinoid structure (a), which leads under electron-impact to the formation of a chlorocyclopropenone ion (c). Secondary routes giving [C_xCl]⁺ ions are also proposed. Emphasis is given to the variations introduced into the fragmentation by the presence of a nitro group.     

Etude en Spectrometrie de Masse de bis Heterocycles Ethers du Resorcinol

The mass spectra of some heterocycles, resorcinol ethers, are examined. We have interpreted the results in terms of the fragmentations of monoheterocycles. No high resolution measurements were made. When there is one benzylic ketone, the decomposition process suggests that the functional heterocycle is cleaved before the other. Each heterocycle appears to participate on the resulting ions unlike in the case of fragmentations of non-functional heterocycles.     

Spectrometrie de Masse du Dimethoxy-2,6 Naphtalene et de Certains de ses Derives

The mass spectra of 2,6-dimethoxynaphthalene and 14 of its derivatives are reported. The fragmentation patterns proposed to account for the main peaks observed are frequently based on the presence of the appropriate metastable peaks. The fragmentation is initiated by the cleavage of an O? CH₃ bond. The molecular ion is the most intense ion in each case and it does not appear to directly eliminate a methoxy group or a substituent directly attached to the naphthalene ring. With NO₂ as a substituent the elimination of nitric oxide from the molecular ion has been observed and confirmed by peak matching.     

Spectrometrie de Masse des Epoxydes Phenyles—II

The fragmentation of aromatic epoxides proceeds either directly through loss of one molecule of aldehyde or ketone which leads to a symmetrical ion, or through rearrangement of the molecular ion into the isomeric carbonyl radical ion. Substituents on the aromatic ring have a marked influence on the fragmentation.     

Etude de la Fragmentation des bis Alkylthio-3,5 Isothiazoles en Spectrometrie de Masse

The study of the fragmentation schemes of twenty-six 3,5-Bis(alkylthio)-isothiazoles allows us to show new fragmentation modes in the isothiazole series. Two important breakdowns could be distinguished in the case of 3,5-Bis(alkylthio)-isothiazoles, from examination of the data concerning the spectra of the deuteriated derivatives in each position concerning the loss of the mer-capto radical and of two atoms of sulphur, respectively. We have shown the specific effect of the thio-alkyl substituents in the cleavage process. A transposition mechanism of the molecular ion is considered to explain the two rival fragmentation schemes.     

Analyse par Spectrometrie de Masse de Derives Fluores en Serie Pyrimidine et Pyrazine

Fluorinated derivatives of trichloro- and dichloropyrimidines and dichloropyrazines have been synthetised and analysed by ¹H and ¹⁹F n.m.r. in association with gas chromatography coupled with mass spectrometry. The behaviour of the compounds under electron-impact is presented and discussed. Attention has been drawn to different mass spectra for distinct positional isomers, confirming the main degradation schemes proposed.     

Analyse en Spectrometrie de Masse de Derives Fluores en Serie Pyrimidine et Triazine

We have synthesised all the fluorinated derivatives of perchloropyrimidine, trichloro-2,4,6-pyrimidine and perchloro-s-triazine. Fluorine n.m.r. analysis, associated with gas chromatography coupled with mass spectrometry, allowed separation and identification of the products. The behaviour of these compounds under electron-impact is presented and discussed here.     

Etude en Serie as-Triazine. XIX—Fragmentations Principales de s-Triazolo-as-Triazinones en Spectrometrie de Masse

The mass spectra of s-triazolo[4,3-b]-, -[3,4-c]- and -[3,2-c]as-triazine-7-ones and their N-methyl derivatives are described. The elucidation of fragmentation pathways is made easy by observation of the changes in m/e values on changing position of the methyl substitution. In all cases a triazine ring fragmentation with initial loss of CO, RCN or RCNCO was observed. This result is characteristic of the different isomeric structures of triazolotriazine-7-ones. The comparison of the spectra of these compounds with those of their N-methyl derivatives shows the occurence of a tautomeric equilibrium, as found from u.v. spectroscopy.     

Etude par Spectrométrie de Masse de la Fragmentation d'une Série de Diols Aliphatiques

The mass spectrometric fragmentation of a series of diols having the general formula HO? (CH₂)_n? OH with n = 2-11 has been studied. Extensive labelling of n-butane-1,4 diol and n-hexane-1,6 diol with deuterium allows fragmentation modes to be proposed. The labelling reveals that intramolecular exchange of H atoms often precedes the fragmentation and becomes more important when the length of the chain increases.     

Phosphates d'enols. XII—Etude en Spectrometrie de Masse de Derives Diethyliques et di-n-Butyliques

The mass spectrometric fragmentations of diethyl phosphates (1) and di-n-butyl phosphates (2) are influenced by the nature of the substituents R, R′ and R″ fixed on the double bond When R = H, the loss of ethylene or 1-butene is mainly observed. When R = CH₃, the double rearrangement process occurs with alkyl group participation of the enolic chain.     

Ionisation et Fragmentation en Spectrometrie de Masse. V—Appreciation de L'Energie D'Activation Pour des Fragmentations Competitives

A competitive kinetic shift has been demonstrated in the course of a molecular ion fragmentation leading to competitive cleavages. A method for the calculation of this ‘competitive kinetic shift’ is suggested.     

Transposition de Cycles Satures en Spectrometrie de Masse III—Etude des Spectres en Basse Tension des Cyclanones

The fragmentation mechanism of cyclanones (cycloheptanone, cyclooctanone and some methylated or deuterated derivatives) was reinvestigated. All the peaks observed can be interpreted on the basis of a rearrangement of the molecular ion. This rearrangement is particularly important at low voltage.     

Spectrometrie de Masse des Acetates de la Serie Bicyclo-(2.2.1) heptane. Elimination de Cetene et Fragmentation Type

Elimination of ketene is shown to occur through a four centre mechanism with the acetates of the bicyclo[2.2.1] series. A typical fragmentation, related to the rearrangements of carbonium ions, is induced by an unsaturation at position 3.     

Transposition des Cycles Satures en Spectrometrie de Masse IV—Dioxolanes Derives de Cetones a Cycle Moyen et Grand

The fragmetation mechanism of cyclanone ethylene acetals in the medium ring and macrocyclic series has been re-investigated. The fragmentation pattern can be explained entirely on the basis of a new rearrangement, involving a ring contraction and hydrogen migrations, which have been checked by using deuterated compounds.     

Etude d'un Couple de Diastereoisomeres en Spectrometrie de Masse: Les 2,3-Diphenyl-butanes Thréo et Erythro

The mass spectra of erythro and threo 2,3-diphenylbutanes are assigned to one rearrangement and one simple cleavage. After calculation of these spectra, it is suggested that their differences are issued essentially from the enthalpy difference of the molecular ions and not from the enthalpy difference between the rearrangement transition states. It is shown that in the gaseous state the threo 2,3-diphenylbutane is more stable than the erythro isomer.     

Etude en Spectrometrie de Masse: VI—Evaluation de l'Induction de la Fragmentation dans les amines β Fonctionnelles

Mass spectra of 22 β-function amines are compared with those of corresponding non-substited amines. Spectral analysis shows that fragmentation is not induceed by the lone-nitrogen atom: keto, ester, amide or nitrile groups also induce this fragmentation and the ratio was evaluated. This very elementary approach, supported by the kinetics of unimolecular reaction is in good agreement with results based on ionisation potential measurements.     

Etude en Spectrometrie de Masse. VIII—Fragmentation de Qulques Benzalacetophenones et Benzalacetones Diversement Substituees sur le Cycle Aromatique

A comparative mass spectrometric study of the behaviour of variously substituted 1,3-diphenylpropenones (or benzylacetophenones) and 4-phenylbuta-2-ones (or benzylacetones) is reported. These compounds are very stable under electron impact owing to the extensive conjugation, which covers practically all of the molecule. The presence of a substituent on the aromatic ring gives characteristic fragments whose significance is discussed.     

Conformation et Spectrometrie de RMN

Examination of PMR spectra of the four 3-dimethylamino-trans-2-decalols and the corresponding quaternary ammonium iodides allows the suggestion to be made that the ordinary double chair conformation usually admitted for trans-decalin is disurbed in the above compounds, especially when the amino and hydroxy groups are (a, e); truer conformations would, in fact, be better represented as ‘flattened chair’ in the case of the dimethylamino compound and ‘twist chair’ in the case of the quaternary ammonium salt.     

Recherches en Serie Azabenzodiazepine. III—Fragmentation en Spectrometrie de Masse de Quelques Pyrido,Pyrimido, Pyrazolodiazepinones,Triazino et Triazolotriazepinones

The mass spectra of several pyrido [2,3-b] and [3,4-b], pyrimido [4,5-b], pyrazolo [3,4-b] diazepinones-1,4 and as-triazino [4,3-b], s-triazolo [4,3-b]triazepinones-1,2,4 are reported and analysed. Five different fragmentation pathways of the molecular ion are generally observed, but the main one is an initial loss of CH₂CO which gives rise to 2-methylazabenzimidazole or 2-methyl azabenzotriazole ions. The behaviour of triazolotriazepines which have two further fragmentation pathways is described.     

Etude en Spectrometrie de Masse d'une Serie d'Anhydride du Type Acetoxy-3 Bicyclo[2.2.2]octene-2 Dicarboxylique-5,6

A series of 3-acetoxy bicyclo[2.2.2]oct-2-ene 5,6 dicarboxylic anhydrides with different substituents is studied by high resolution mass spectrometry. The spectra obtained are complicated and can only be differentiated by the presence of certain peaks and their variable relative abundances. We have almost entirely explained these peaks by the use of classic degradation mechanisms. We have applied the explanations advanced by Cimarusti and Wolinsky for a series of analogues.The degradation scheme is very similar for all the products, and is unaffected by the substituents and their relative position.