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 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.     

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 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.     

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.     

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 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 de la fragmentation de derives de L'uracile et de la thymine par Spectrometrie de masse

Original mass spectra of uracil and thymine derivatives are presented with the corresponding fragmentation schemes. In the first series of spectra, the fragmentations of thymine derivatives, including ¹⁴C-2-thymine, dimers, and bromo thymines, confirm the basic retro Diels-Alder mechanism. The second series includes dihydro 5,6-derivatives of uracil (hydroxy and bromo substituents). The behaviour of these molecules is quite different; they are more sensitive to the substituents and a part of the fragmentation is often explained by protonated molecular ions.     

Etude par spectrométrie de masse de la fragmentation du désoxy-3-di-O-isopropylidène-1,2: 5,6-méthylidène-3-α-D-hexofurannose et de quelques analogues substitués en C(3′)

Electron Impact Mass Spectrometry of the 3-Desoxy-1,2: 5,6-di-O-isopropylidene-3-methylidene-δ-D -hexofuranose and Some C(3′)-Substituted Analogues The mass spectra of the 3-desoxy-1,2:5, 6-di-O-isopropylidene-3-methylidene- α-D -ribo-hexofuranose and of some C(3′)-mono- and -disubstituted derivatives have been investigated. Deuterium labelled molecules allow fragmentation modes to be proposed.     

Etude de la fragmentation par impact électronique de dérivés du benzothiazole

Study of Electron-Impact Fragmentation of Benzothiazole Derivatives The mass spectra of eighteen substituted benzothiazoles are reported and discussed. All these compounds are thermodynamically stable and give an intense molecular ion, which undergoes different types of fragmentation depending on the nature of the substituent which is rarely eliminated directly. β-Cleavage with respect to the heterocyclic double bond is often observed. Specific ²H-, ¹³C-, ¹⁵N- and ³⁴S-labelling have been used in order to confirm the fragmentation patterns.     

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).     

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 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.     

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.     

Etude de la fragmentation des alkyl-thiazoles en spectrographie de masse

The mass spectra of 27 mono-, di- and trisubstituted alkyl-thiazoles are reported and discussed. The predominant fragmentation is characterized by the loss of R²CN with formation of a thiiren-ion and the β-cleavage with respect to the cyclic double bonds.     

Etude par RMN du proton de la complexation du triéthylaluminium par l'éther diéthylique

The complex between triethylaluminium and diethylether has been studied by ¹H NMR; separate signals have been observed for free and bonded triethylaluminium. From the area ratios, a 1:1 stoichiometry is demonstrated. At higher ether concentrations, chemical shift measurements prove that other complexes do not appear.     

Utilisation du 13C en Spectrométrie de Masse: Etude de la Fragmentation de Disaccharides

Twenty-nine α,β-(1 → 3) and (1 → 4) or β-(1 → 6) disaccharides, in the glucose series were analysed by electron impact mass spectrometry. In addition to the known mechanism, a few ¹³C labelled compounds led us to suggest that the ion c was formed from the reducing unit B and the C-1′ of the non-reducing residue A, while A was the starting point for rearrangement and fragmentation processes.     

Etude sur les composés organométalliques. XII [1]. Etude de composés tétraorganiques du titane par spectrométrie de résonance magnétique nucléaire

Tetrabenzyltitanium, tetraphenyltitanium, and tetramethyltitanium were studied by using NMR. spectroscopy. The spectrum of tetrabenzyltitanium depends on the procedure of its preparation. An interpretation of this finding is proposed.     

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.