Etude des fragmentations en spectrographie de masse de dithiolannes-1,3 substitués en 2 par des groupements insaturés

The mass spectra of the title compounds always show an intense molecular ion. Some fissions involve loss of the ethylenic group, while others are related to cleavage of the dithiolane ring, eventually followed by recyclizations involving the ethylenic chain, due to which resonance structures can be written. If a phenyl group is present in the ethylenic chain, the spectra are modified due to the formation of the very stable benzothiopyrylium ion.     

Additions radicalaires du tétrahydrothiophène à des dérivés éthyléniques: Préparation de tétrahydrothiophènes substitués en 2

Di-t-butyl peroxide induces a free radical addition of tetrahydrothiophene to ethylenic compounds. The main products arise from an α-attack of the substrate. This reaction seems to be an interesting synthesis of these heterocycles.     

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.     

Eliminations competitives lors de la decomposition basique de sels de N-alcoxypyridinium—I: Competition entre intermediaires ylure ou anhydrobase et ions hydroxydes dans l'arrachement des protons en α ou β dans la chaine alcoxyle2

A novel mode of base-induced decomposition of N-alkoxypyridimum salts carrying a β-hydrogen in their alkoxy chain is described. In these compounds the N-oxide moiety can act as a leaving group in an elimination reaction yielding an ethylenic derivative, in competition with the classical decomposition to aldehyde and pyridine. This latter is predominant in salts 9 and 10 bearing a methyl group in 2 or 6 positions of the pyridine nucleus, whereas the new mode of decomposition becomes almost exclusive for salts 7 and 8 unsubstituted in these positions. Deuteration studies show that proton abstraction does not occur by transfer to an ylide during the decomposition by hydroxide ion, proton abstraction results from direct attack by hydroxide ion except for the α-proton of salts bearing at least one methyl group in 2 or 6 positions where it occurs by a transfer (essentially intramolecular) to an intermediary anhydrobase.     

Fragmentation des aldehydes cyclopropaniques en spectrometrie de masse: Intervention d'interactions bifonctionnelles

The mass spectra of aliphatic aldehydes which contain a cyclopropane group included in the polymethylenic chain, in some instances, show two intense peaks, called A and B that are not encountered either in other cyclopropane-containing aliphatic compounds or in other aliphatic aldehydes. The intensity of peaks A and B is strictly dependent upon the distance between cyclopropane and aldehyde. When the number x of methylene groups between the two functions is equal to 4 or higher than 10, peaks A and B are intense, but when x is equal to 7, the peaks are small.Specific labelling shows that ion A contains the atoms of the cyclopropane ring, the polymethylenic chain between the two functions and the aldehyde function. Ion B also contains the aldehyde function and results from the expulsion of the polymethylenic interfunctional chain to which a hydrogen atom of the other part of the molecule is added. This hydrogen atom arises, to an extent of about 60%, from the methylene of the cyclopropane ring. A mechanism is proposed in which cyclization of the molecular ion occurs; ion A is obtained by direct α-cleavage to the ether function in the cyclic ion; ion B results from alternative ether-cleavage causing opening of the carbo-ring. One hydrogen from the cyclopropane ring is transferred leading to the elimination of the interfunctional chain.The fact that formulas of ions A and B correspond to [C_nH_2n-3O]⁺ and that their intensities are dependent of x make questionable any structural determination established only by mass spectral examination of cyclopropane aldehydes.     

Phosphates D'énols: XI—Étude en Spectrométrie de Masse des Dérivés Diméthyliques

The mass spectrometric study of a series of enolic phosphates of type A leades to fragmentation patterns influenced by the nature of the substituents (R, R′ and R″). It is generally observed that a simple or double hydrogen rearrangement occurs with the loss of the enolic groups. When R and R′ are alkyl groups, the migrating groups are the hydrogen atoms on the alkyl group at position 1. When there is no alkyl group at position 1, the hydrogen atoms of the alkyl group at position 2 induce the rearrangement process. Finally, if R, R′ and R″ are hydrogen atoms, the loss of the enolic chain occurs without any rearrangement.     

Étude en RMN du 13C de Dérivés de la Pipéridone-4 Stériquement Encombrés et des Oximes Correspondantes

The regiospecific differences in chemical shifts caused by the oximino group, such as Δδ as Δδ parameters, are useful to estimate conformational distortions directly from ¹³C spectra. Particularly, twist-boat conformations resulting from oximation of sterically hindered piperidones are unambiguously detected.     

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.     

Ionisation Chimique de Composés Aromatiques Nitrés

The collision induced dissociations of [MH – 30]⁺ ions observed in the chemical ionization (methane) mass spectra of some nitro aromatic compounds show that these ions are formed by reduction in the ion source with subsequent protonation and not by the previously reported losses of NO^· from the protonated molecular ions.     

Hétérocycles contenant du phosphore. XXII—Etude par RMP de dérivés de l'oxazaphospholane-1,3,2: II—Analyse des spectres de composés monosubstitués en 5 ou disubstitués en 4 et 5.

The influence of various factors (temperature, nature and concentration of solvent) or the utilisation of various physical methods (tickling or INDOR experiments, for example) are employed to analyse the PMR spectra of some 5-monosubstituted or 4,5-disubstituted 1,3,2-oxazaphospholane derivatives.     

Heterocycles contenant du phosphore-XXI. Etude par RMP de déeriveés de l'oxazaphospholane-l,3,2: I-Analyse des spectres des composksés non substitués en 4 et 5.

The PMR spectra of the title 1,3,2-oxazaphospholane derivatives present an ABKLX pattern. The subspectral analysis of such a system shows that there are eight solutions. INDOR experiments permit the establishment of the energy diagram and the selection of the correct solution.     

Spectres de masse des composés organiques. 3e Communication.. Perte de méthyle dans la fragmentation des alcanes

The reaction mechanism for the loss of methyl and methane from the parent ion is investigated for n-alcanes. By using different deuterated species, mainly hexanes, it is shown that these two reactions proceed by two paths, one being the simple split of a C-C-bond, whereas the other consists in an internal rearrangement followed by a loss of a C-atom from within the chain. This process is becoming the main process for this class of fragmentation as the hydrocarbon chain is getting longer. A small internal isotope effect has also been found.     

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.     

L'indice de rétention des alcanes isomères en chromatographie en phase gazeuse

A method, using the radiolysis of an alkane, for the obtention of a great number of branched hydrocarbons is given. The retention index at 100° as well as its variation with temperature is determined on Apiezon L for 200 alcanes containing between seven and twenty four carbons. It is shown that for branched hydrocarbons the decrease of the retention index is mainly due to the length of the substituent group but also to its position on the chain. Some rules between retention index and molecular structure are deduced that allow the determination of the index of higher branched hydrocarbons. It is also shown that the variation of the retention index with temperature is only a function of the length of the substituent group.     

Etude de composés d'addition des acides de Lewis XXVIII. Constantes de Hammett et vibration carbonyle des composés formés par TiCl4 et SbCl5 avec des chlorures de benzoyle parasubstitués

The adducts of benzoyl chlorides p-substituted by CH₃O? , CH₃? , and H? with the electronic acceptors SbCl₅ and TiCl₄ have been prepared, and the IR. absorption spectra of the solid products studied.     

Synthèse et étude structurale de dérivés substitués en -2 du thiazolidine carboxylate d'éthyle-4 (R)

Pharmacological properties of thiazolidine derivatives are of great interest. For this purpose we prepared two series: 2-hydroxyalkyl-4-carbethoxythiazolidines and 2-carbalkoxyalkyl-4-carbethoxythiazolidines. Their syntheses involve a condensation reaction between L-carbethoxy-cystein and several α-hydroxyketones or β-ketoesters. Compounds 4 and 5 was obtained as an unequal mixture of diastereoisomers. Protons nmr spectra at 300 MHz in the presence of trifluoroacetic acid shows a modification of diastereoisomer percentages which indicate the existence of an equilibrium through an imminium ion intermediate. Therefore, the stereoselectivity observed reflects the relative stability of the different diastereoisomers.     

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.     

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.     

Analyse topologique du comportement d'esters aliphatiques saturés et insaturés en chromatographie gaz-liquide

(Topological analysis of the gas-liquid chromatographic behaviour of saturated and unsaturated aliphatic esters.) Topological analysis is applied to tje Kovats retention indices for a collection of aliphatic esters on six stationary phases. Three subclasses are treated separately: (1) 100 saturated esters; (2) 45 esters unsaturated in the acidic part and 53 saturated but topologically similar esters; (3) 24 esters unsaturated in the alcohol moiety and 6 saturated but topologically similar esters. A detailed study is reported for the correlation of structural effects with numerical data for the specific solute/stationary phase interactions at the level of carbon atoms and ethylenic double bonds. The roles of the carboxylic ester nucleus, the branching and lengthening of the chain and the presence of ethylenic double bonds is elucidated. The selectivity of trifluoropropyl- and phenyl-bonded stationary phases is clarified.     

Spectrographie de Masse de Diazastéroïdes Possédant le Motif Tétrahydroisoquinoléique

We have determined the characteristic fragmentations in a series of 3,4-dihydroisoquinoline and of 8,13 diazaestrones, with the aid of metastable ions, ‘simili’ mass analysed ion kinetic energy spectra (E/V² constant) and some deuterated compounds. In the diazasteroidal series, we could distinguish three essential types of fragmentation, as well as preferential abstraction of the hydrogen situated on the 14-carbon.