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.     

Spectres photoélectroniques de la dithiole-1,3-thione-2 et de son dérivé benzosubstitué

The photoelectron spectra of 1,3-dithiol-2-thione and its benzo-substituted derivative have been analysed in terms of orbital interactions. Comparison of the P.E. spectra of these compounds and ethylene trithiocarbonate and 2-methyl, ethyl-benzo-1,3-dithiol permitted the influence of the spatial configuration of molecules and of the C=S group on the electronic structure of these cycles to be evaluated.     

Etudes Conformationnelles par Résonance Magnétique Nucléaire d'Ethanes Disubstitués par un Hétéroatome appartenant aux Colonnes IV,V et VI et par un Groupement Fonctionnel

In this paper results obtained in the conformational analysis of ethers, sulphides, selenoethers, amines, arsine, germanes and stannanes such as R? X? CH₂? CH₂? Y are given. The AA′BB′ part (–CH₂? CH₂–) of the NMR spectra was studied by a method using chemical shifts. The electronegativity of the heteroatom was connected with the difference of the chemical shifts of AA′BB′. Following this, conformational analysis based on NMR spectra obtained at different temperatures permitted us to show that in the temperature range used (230 K–320 K) triphenylstannyl-3 propionitrile has a ‘blocked structure’.     

Structure électronique de dérivés sulfurés : Partie V. spectres électroniques d''hétérocycles thio-carbonylés

The experimental and theoretical spectra of thiocarbonyl heterocyclic compounds with two heteroatoms in the position to the thiocarbonyl group have been studied.

The theoretical interpretation of the CNDO/S results including an extension to the third period, i.e. 3d orbitais, is in good agreement with the saturation effect as well as with the influence of the intracyclic heteroatoms on the typical absorptions of the thiocarbonyl group.     

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.     

Étude de l'effet de solvant en résonance magnétique nucléaire—I Caféine et dérivés

The NMR spectrum of caffein shows three N---CH₃ peaks. By study of solvent effect and pH effect on this spectrum, it was possible to make a correct attribution of the absorption peaks. A proof of this attribution was searched in the examination of NMR spectra of theophylline and theobromine. Two new chlorocaffeins were prepared during this work.     

Etude Comparée de la Fragmentation de Trois Composés Médicamenteux a Structure Hétérocyclique: la Primaclone,le Glutethimide et le Phenobarbital

Mass spectra obtained from the three title compounds were compared. High resolution studies and deuterium labelling allowed a proposal for an original cracking pattern, typical of the structure. The postulated mechanism involves a six-centred cyclic electron transfer, generating an aromatic radical ion. Cracking patterns characteristic of barbiturates could also be observed.     

β-Dicéto énamines hététrocycliques: 1. Indanediones-1,3 substituées en 2 par un hétérocycle azoté

The condensation of methylated N-heterocycles and espically monomethyl- and polymethylpyridinets on phthalic enhydrides leads to 2-ary1-1,3-indanediones. The 3alklidenylphthalides formed in an intermediary state have been isloated. The influence of solvents and temperature on the velocity and yeild of formation of 2-(2- and 4-pyridyl)-1,3-indandiobnes has been studies. The ir and nmr spectra confirm taht these compunds exist under a β-diketoenamine form resonating witj a betaine form.     

Tétraméthylidène-2, 3, 5, 6-oxa-7-bicyclo[2.2.1]heptane. (Communication préliminaire)

Preparation of the title compound ( 4 ) is described. An important transannular effect between the two unconjugated s-cis-butadiene chromophores is observed by comparison of the UV. spectra of the dimethylidene-oxanorbornane 3 and the tetramethylidene-oxanor-bornane 4 .     

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).     

Etude de la fragmentation par impact électronique en ions positifs et négatifs de dérivés nitrés de l'amino-2-benzothiazole

Study of Positive and Negative Ions Electron Impact Fragmentation of 2-Amino-benzothiazole Nitro Derivatives The positive and negative ions mass spectra of 2-amino-4,6-dinitrobenzothiazole ( 1 ), 2-amino-4-nitrobenzothiazole ( 2 ), 2-amino-6-nitrobenzothiazole ( 3 ) are reported and discussed. These compounds give an intense molecular ion and show interesting fragmentations in both positive and negative ions spectra. Specific ¹⁵N-labelling was used in order to confirm the fragmentation patterns.     

Acide glyoxylique Symétrie de la molécule libre, spectres de vibration et attribution

The infrared and Raman spectra of glyoxylic acid in the gas phase, in solution and in the solid state have been obtained in the region from 4000 to 300 cm⁻¹. p]Band structure analysis in the gaseous state shows that the configuration of formyl-carbonic acid is trans and planar. It was established that in solution some bands belong to dioxyacetic acid. p]A vibrational assignment is proposed based on a priori calculation of the spectra, using a Urey-Bradley force field intermediate between those of glyoxal and oxalic acid.     

Synthèse et Propriétés d'Alkylidénehydrazono-2 Méthyl-3 Dihydro-2,3 Benzothiazoles

The synthesis and the spectral properties of 2-alkylidenehydrazono-3-methyl-2,3-dihydrobenzothiazoles are reported. In the mass spectra of each of these compounds, the main fragmentation implies the breaking of the ?N? -N?bond of the azine.     

Hétérocycles contenant du phosphore: XXVII—Etude par Résonance Magnétique Nucléaire de quelques dérivés des dioxa-et dithiaphospholanes-1,3,2 monosubstitués en 4

The ¹H n.m.r. spectra of some derivatives of 4-methyl (or 4-phenyl) 1,3,2-dioxa- and 1,3,2-dithiaphospholanes are analysed. The configurational study of the compounds has been investigated. The torsional angle of the C₄? C₅ fragment is calculated and the ring conformation in solution is discussed.     

Sur l'Utilisation de la Stéréospécificité des Couplages Magnétiques à Longue Distance dans la Détermination des Conformations d'Aziridines Bicycliques

The study of long range coupling constants in the ¹H NMR spectra (60 MHz) of aziridines with a 7-azabicyclo[4.1.0]heptane skeleton allows the determination of the conformation of these compounds and shows that some isomers have a rigid structure.     

Structure électronique, spectre ultraviolet et solvatochromie du tétracyano-1,1,3,3 aza-2 propénure de tetramethylammonium

CNDO/S calculations are performed for the [(CN)₂-C-N-C-(CN)₂]⁻ anion. The observed and theoretical ultraviolet spectra are in perfect agreement. A theoretical analysis of the electronic structure and solvation energy of ground and excited singlet states confirms the almost total lack of sensitivity of the electronic spectrum to solvent effects.     

Low-energy,low-temperature mass spectra. 9—The linear undecanols

The 70 and 12 eV mass spectra of the six linear undecanols are reported. Apart from undecan-1-ol, whose spectrum is akin to that of undec-1-ene, the spectra are dominated by peaks corresponding to loss of water and α-cleavage. The low voltage spectra are more readily interpreted.     

Résolution de spectres RPE par régression non linéaire. Application à des radicaux anions dérivés de thiazoles substitués

A non-linear regression method for the resolution of EPR spectra is described. The theoretical model is fitted with the experimental spectrum and the error on each parameter is calculated. The method is applied to the radical anions of 2-nitro-4-methyl thiazole, 4-p-nitro-phenyl-thiazole and 5-p-nitro-phenyl-thiazole.     

Hétérocycles des Eléments du Groupe IV. VII—Spectrométrie de Masse de Silacyclopentènes

Mass spectra of substituted silacyclopentenes have been studied. The fragmentation mechanisms observed are similar to those for germacyclopentenes. The most important conclusions are retention of the charge on the heteroatom, hydrogen migration, silyl ion formation and expulsion of substituents linked on the heteroatom.     

13C RMN: Non-équivalences d'ammoniums quaternaires diastéréoisoméres

¹³C magnetic resonance spectra of six diastereomeric mixtures of quaternary ammonium salts were investigated. Assignment of the signals of the non-aromatic carbons and measurement of the non-equivalences allowed the determination of the ratio of isomers in the mixtures. A deshielding β effect and a shielding γ effect for the quaternisation were pointed out.