Etude de cyclohexanediols par spectrométrie de masse

Low resolution mass spectra of cyclohexane-1,2-diols and of deuterium labelled cyclohexane-1,2-diols cis and trans have been measured. The results indicate that it is easy to differentiate between positional isomers and that the stereochemistry of cyclohexane-1,2-diols can be deduced from the mass spectra. In the 1,2-diols the elimination of water under electron impact occurs simultaneously in three ways: (a) between an OH group and a H atom in position 1,4, (b) between the two OH groups, (c) without participation of the II atoms of the OH groups. Difficulties encountered in deducing unambiguous fragmentation patterns are discussed.     

Etude par spectrométrie de masse de l'ionisation de benzonitriles,de phénylacétonitriles et de N,N-diméthylanilines substitués

Molecular ionization potentials for series of compounds of the type X? C₆H₄? CN, X? C₆H₄CH₂? CN and X? C₆H₄? N(CH₃)₂ have been measured using the retarding potential difference technique (RPD. technique). The effect of the various substituents X is better correlated through the electrophilic Brown σ_p⁺ constants than through Hammett's σ_p values. No meta-para orientation effect is observed. For all the disubstituted phenyl compounds studied, the effect of the second substituent is affected by the electron-releasing power of the original substituent. Ionization potentials calculated by using the semi-empirical method of equivalent orbitals are in good agreement with the experimental values.     

Etude par spectrométrie de masse du cyclopentanediol-trans-1,2

The electron impact induced fragmentation of trans cyclopentane-1, 2-diol has been investigated using derivatives specifically labelled with deuterium and high-resolution mass spectral data. The elimination of the elements of water from the molecular ion involves at least three mechanisms whose relative importance has been evaluated. A fragmentation scheme based upon metastable peaks and labelling is presented.     

Etude par spectrométrie de masse de la fragmentation des cyclopentane-triols-1,2,3, des cyclopentane-tétrols et des cyclopentane-pentols

The mass spectra of the three cyclopentane-1,2,3-triols, six cyclopentane-tetrols and four cyclopentane-pentols stereoisomers have been studied. Complex processes, especially regarding the H₂O eliminations, were detected by extensive deuterium labelling.     

Caractérisation de nouveaux dérivés et analogues de la nétropsine et identification de leurs intermédiaires de synthèse par spectrométrie de masse FAB

The fast-atom bombardment (FAB) mass spectra of a series of netropsin derivatives and analogues were examined in positive-ion and when necessary negative-ion modes. Behaviour of these derivatives was related to that of oligopeptides. Some compounds protected by t-butoxycarbonyl groups were also investigated using this technique and showed characteristic fragmentations.     

Etude par spectrométrie de masse de la fragmentation du cyclopentènediol-3,5-trans

The decomposition modes of trans cyclopentene-3, 5-diol under electron impact have been studied on deuterium labelled analogues. Fragmentation mechanisms are proposed.     

Influence de la vitesse de chauflage sur l'atomisation électrothermique en spectrométrie d'absorption atomique. Applications aux éléments volatils, cadmium et plomb

The advantages of electrothermal atomization by rapid heating (faster than 2000°C s⁻¹) in atomic absorption for the determination of volatile elements are studied. The aim is to control the matrix effects, particularly the very high non-specific absorptions. It is shown that, unlike normal heating, now rapid heating makes it possible to atomize a volatile element without hardly covolatilizing its matrix, as a result of the change in the optimum atomization temperatures.Application examples are given: direct determination of cadmium and lead (atomized respectively at only 900 and 960°C) in sea water and related products. This method is likely to be applicable to other matrices which covolatilize normally with other elements. The mechanisms of atom formation in rapid heating are also investigated.     

Recherches dans la série des cyclitols XXXVII Etude par spectrométrie de masse

Low resolution mass spectra of cyclohexane-triols, -tetrols, -pentols and -hexols and of some of their deuterium labelled derivatives have been measured. The results indicate that for some geometrical isomers quantitative differences between ion intensities are significant, allowing to deduce the stereochemistry of the molecule from its mass spectrum. In all these compounds the electron impact induced elimination of water occurs mainly by interaction between OH groups. There is a correlation between the relative abundance of (M – H₂O)⁺ and (M ?2 H₂O)⁺ ions and the number of axial hydroxyls in the more stable conformation of the molecule. Difficulties encountered in deducing fragmentation patterns, and determination of number and position of deuterium atoms in the molecule of ms-inositol are discussed.     

Etude par spectrométrie de masse des cyclopenténols,cyclopentène-diols-3,4 et cyclopentène-triols-3,4,5

The mass spectra of cyclopentene-1-ol-3, -1-o1-4, those of cis- and trans-cyclopentene-3,4-diol and of the three stereoisomers of cyclopentene-3,4,5-triol have been studied. Decomposition modes based upon results obtained using deuterium labelled analogues are discussed.     

IsoméRisation avant la perte d'eau des ions aldéhydes et cétones protonés en spectrométrie de masse

Isomerization of Protonated Aldehyde and Ketone Ions in the Mass-Spectrography Before the Loss of Water In mass spectrometry, protonated aldehyde and ketone ions isomerize before the loss of a molecule of water. In order to specify this process, the spectra of deuterium labelled protonated aldehydes and ketones have been compared to the spectra of the corresponding isomer ions.     

Recherches en série diazépine-1,4 et triazépine-1,2,4. XI—etude en spectrométrie de masse des fragmentations de triazépines-1,2,4

The mass spectra of eleven 1,2,4-triazepines with oxo, thioxo, methoxy and methylmercapto groups in the 3 and 5 positions are reported and analysed. Each of the five structures of the triazepine ring present is characterized by a particular group of fragmentations.     

Mécanismes de fragmentation en spectrométrie de masse par ionisation chimique. III—ions formés par cyclisation

Chemical ionization mass spectrometry of bifunctional organic molecules can induce fragmentation involving the formation of cyclic ions.     

Etude par spectrométrie de masse d'une série d'alcanediphtalimides-α,ω

Mass spectrometric study of a series of alkane-α,ω-diphthalimides Alkane-α,ω-diphthalimides with three to seven aliphatic C-atoms were synthesized and their mass spectral behaviour investigated in detail with the aid of the deuteriated derivatives of hexane-1,6-diphthalimide. Besides the expected hydrogen rearrangements, an interesting skeletal rearrangement has been observed.     

Etude par spectrométrie de masse des O-isopropylidène-1,2-thréo- et -érythro-furannoses et des quatre désoxy-5-O-isopropylidène-1,2-pentofurannoses

The mass spectra of the O-isopropylidene derivatives of threo- and erythro-furanose and those of the four C(4) methylated stereoisomers have been studied. Fragmentation modes based upon deuterium labelling, metastable peaks and high-resolution measurements are proposed. Each stereoisomer can be characterized by its low-resolution mass spectrum.     

Recherches en série azabenzodiazépine. VI—etude en spectrométrie de masse de pyrazolo [3,4-b]diazépines-1,4

The mass spectra of 21 1,4-pyrazolo[3,4-b]diazepines are reported and analysed. Each of the five structures of the diazepine ring present is characterized by a particular group of fragmentations; among them one is common to all the compounds under study: the cleavage of C-5? C-6 and C-7? N-8 bonds leading to pyrazoloimidazoles ions.     

Etude par spectrométrie de masse du diaza-2,5 dioxa-1,6 thia-6a λ IV pentalègne et de ses analogues séléniés et tellurés

The mass spectra of 2,5-diaza-1,6-dioxa-6a-λ-IV-pentalenes and of its selenium and tellurium analogs are recorded. The spectra show strong stability of these compounds under electronic impact and a rather good reproductibility for their fragmentations independently of thenature of the heteroatom (s, Se or Te).     

Conformation et Spectrometrie de RMN. III. Spectres 13C de Diméthylamino Cyclanols et Dérivés

The ¹³C NMR spectra of 2-dimethylaminocyclohexanols and the four trans-3-dimethylamino-2-decahydronaphtols are described. The gauche interactions allow precise estimation of chemical shifts for each carbon atom; thus, band attribution can be resolved without mistake. In the case of the cis and the trans diequatorial compounds, the conformational perturbations which we have suggested before are verified by our present measurements on the substituted carbon atoms. We also show effects on adjacent atoms, which were unobservable with the usual IR and ¹H NMR techniques.     

Etude par Spectrométrie de Masse de Silanes et de Stannanes Aromatiques

The mass spectra of six compounds of the type Et₃Si? C₆H₄? ZR_xR_3?x (R=Et, R′ = CI, Z = Si, Sn) have been measured. The fragmentation patterns can be interpreted on the basis of an ionized hexa-1,3-diene-5-yne intermediate.     

Spectrométrie de masse. Fragmentations induites par impact électronique d'amino et de diméthylaminopyrimidines

Ekectron-impact mass spectra are presented for some amino and dismethylaminopryimidines. In the two series the base peak is due to the moleculer ion. In the former, the fragmentation pathway invovles loss of hydrogen cyanide from the moleculer ion, whereas in the latter, it is the loss of methyl or methylenimine CH₂?NH that occurs. The presence of HNMe₂⁺ ion for 4-dimethylaminopyrimidine allows one to differentiate this isomer from 2-dimethylaminopyrimidine.