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 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.     

Etude par Spectrométrie de Masse d'une Série de Phényl-1 Naphtalènes Substitués et des Dihydro-1,4 Naphtols-1 Correspondants

The 70 eV electron impact mass spectra of a series of substituted 1-phenylnaphthalenes and their corresponding 1,4-dihydro-1-naphthols have been studied. Plausible fragmentation modes which account for the formation of all the major ions are proposed. An interesting hydrogen transfer reaction, leading to major fragments through the elimination of methanol, seems to proceed via an 8-membered transition state mechanism.     

Étude D'une Série de Phénoxazines et D'azaphénoxazines par Spectrométrie de Masse

Mass spectra of substituted phenoxazines and azaphenoxazines have been determined and are discussed here. These compounds are characterised by hydrogen on the heterocyclic nitrogen and aromatic rings with nitro groups and chlorine as substituents. The fragmentation patterns are explained by known mechanisms. An interpretation of almost all the peaks is offered. The presence of the substituents causes a complete change in the fragmentation patterns compared with the unsubstituted phenoxazine. This is due to changes in charge localisation, caused by the substituents. Isomerisation of the nitro group to the nitroso group gives rise to a particular fragmentation route.     

Fragmentation en Spectrométrie de Masse D'Imidazobenzodiazépines

The mass spectra of a series of imidazo[4,5,1-jk]1,4-benzodiazepines and imidazo[1,5,4-ef]1,5-benzodiazepines have been examined. The differences in the fragmentation patterns permit the isomeric structures to be identified.     

Spectrométrie de Masse D'hétérocycles Séléniés. III—Etude de la Fragmentation de Quelques Selenolo [2, 3-b] Pyridines

The mass spectra of thirteen selenolo[2,3-b]pyridine derivatives have been measured and compared with those of benzo[b]selenophene, quinoline and thieno[2,3-c]pyridine. The influence of diheteroatomic structure of the nucleus on the mechanism of fragmentation of the oxygenated substituents is discussed.     

Mécanismes de Fragmentation en Spectrométrie de Masse par Ionisation Chimique. IV—Fragmentation des Ions Oxiranes Protonés

Fragmentation of oxians after chemical ionization, leading to the loss of water, involves several steps. The opening of the ring is the determining step. The potential energy surface of this reaction is given for the 2-methyltetrahydrofuran.     

Etude par Spectrométrie de Masse du Di-O-isopropylidene-1,2;5,6-α-D-ribo-hexofurannosul-3-ose

The electron impact mass spectrum of 1, 2:5, 6-di-O-isopropylidene-α-D -ribo-hexofuranos-3-ulose has been studied. Fragmentation modes based upon deuterium and ¹⁸O labelling are proposed.     

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.     

Ionisation et Fragmentation en Spectrométrie de Masse. VI—Energie d'Activation de la Fragmentation Principale des Monohalogénobenzènes

The activation energy of the fragmentation [C₆H₅X?]⁺ → [C₆H₅]⁺ + X? (X = Cl, Br, I) is calculated by various methods. These results are compared with determinations of kinetic energy release and with rate constant values available in the literature.     

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.     

Spectrométrie de Masse de Benzylidène—Acétals d'Hexopyranosides

The electron impact fragmentation is reported for 46 benzylidene acetals of hexopyranosides of the allo, altro, galacto, gluco, gulo and manno series and some of their mono-oxidation products. Besides the molecular ion, which is always present and is usually part of a triplet the previously reported ion formed by cleavage of C-1? C-2, C-4? C-5 and the benzylic C? O(C-4) bond is observed. Evidence is given for two complementary ruptures (C-1? C-2, C-3? C-4; C-1? O-5, C-2? C-3, fragmentations whose intensities depend on the substituents or functional groups present in the molecule. In most cases these fragmentations allow an assignment of the substitution mode of these 1,3,6-trioxa-bicyclo-[4.4.0]decane systems. The limitations of this method are discussed.     

Etude en Spectrométrie de Masse. X—Fragmentation d'Ethanes Disubstitués par un Hétéroatome des Colonnes IV,V et VI,et par un Groupement Fonctionnel

In this paper, the behaviour of ethers, sulfides, selenoethers, amines, germanes and stannanes, substituted on the β-C by a methoxycarbonyl, methyl ketone, or cyano group is compared and discussed. The compounds containing group V_B or VI_B element are quite stable, while those with a group IV_B element fragment very easily. Fragmentation α to the heteroatom gives peaks for which the intensity increases with the size of the element:[PhO]⁺<[PhS]⁺<[PhSe]⁺<[Ph₃Ge]⁺<[Ph₃Sn]⁺. Fragmentation at the β position gives very important peaks when the ionization potential is low or when the substituents inductive effect is strong (CN<CO₂CH₃<COCH₃).     

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.     

Spectrométrie de Masse D'Hétérocycles Azotés. VI—Tautomérie en Phase Gazeuse d'Isoxazolones-5

A comparison of the fragmentation under electron impact of isoxazol-5-ones with those of their methylated derivatives (5-methoxy isoxazoles, 2-methyl isoxazol-5 ones and 4-4-dimethyl isoxazol-5 ones) shows that in the vapor phase and prior to the fragmentation, the isoxazol-5 ones exist in the CH tautomeric form. Furthermore, in the case of the 5-methoxy isoxazoles, it has been established that the rearrangement isoxazole→azirine→oxazole which occurs thermally, leads to a variation in the intensities of some ions depending on the experimental conditions.     

Spectrométrie de Masse d'Hétérocycles Azotés. X–Contribution à l'Etude du Comportement de ll'Ion Aniline et des Ions Aminopyridines avant Fragmentation par Perte de HCN

The study of the mass analysed ion kinetic energy spectra of deuterated derivatives of aniline, aminopyridines and 2-chloro-5-aminopyridine shows that prior to HCN loss, hydrogen scrambling does not occur for aminopyridines and is limited but noticeable for aniline. In the case of this last compound the extent of scrambling varies markedly for small variations in the energy of the ions studied, these variations being within the energy window corresponding to metastable ions. Furthermore, an examination of the mass analysed ion kinetic energy spectra of monodeuterated derivatives of aminopyridines leads to the rejection of the generally accepted mechanism for HCN loss from the molecular ions of these compounds.     

Orientation de la Fragmentation en Spectrométrie de Masse Par Introduction de Groupements Fonctionnels. XII—Ethylene Acetals Derives de Cyclopentanones et Cyclopentanones α Substituees

The mass spectrometric fragmentations of ethylene ketals corresponding to α substituted ketones were re-examined. A new type of rearrangement has been established.     

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.     

Etudes d'Hétérocycles Pentagonaux Polyhétéroatomiques par RMN du 13C. Effets de Substituant,de la Benzocondensation et Etude de la Tautomèrie Prototropique en Série Benzothiazolique

The ¹³C NMR spectra of 43 benzothiazoles have been recorded in DMSO-d₆. All carbon atoms have been attributed in an unambigous way owing to substituent effects in position 4, 5, 6 or 7. We discuss variations of chemical shifts as a function of the nature of the substituent in position 2 (equation of type: Δδ = aF+bR+cQ+d′), annelation in the benzoheterocyclic series, and prototropic tautomerism in the benzothiazolic series (in the case of the substituent in the 2-position being an OH, SH or NHR group).