Spectres de masse des composés organiques. 5e communication. Perte de méthane et d'éthylène à partir des ions butyle

The loss of methane and ethylene in the mass-spectrometric fragmentation of different isomeric butyl ions which originate from butyl halides has been studied. The different carbon atoms in n-butyl are already equivalent after 10^?7 s, whereas the statistical distribution of the hydrogen atoms within the molecule can only be observed for the metastable peaks. A protonated cyclobutane structure is proposed as an intermediate product in the fragmentation of the n-butyl ion. The fragmentation of this model has been simulated by a computer. This allows prediction as to the time-scale of fragmentation. The comparison of this model fragmentation with that of isomeric butyl ions shows that, even in the decay of the tertiary butyl ion, the formation of the proposed rearranged cyclic structure competes favorably with the direct fragmentation.     

Ionisation et Fragmentation en Spectrométrie de Masse. VII—Structure de l'Ion [C6H6O]+ Issu de la Décomposition du Phényléthyléther Sous Impact Electronique

The activation energy is calculated for the fragmentation [C₆H₅OC₂H₅]⁺ → [C₆H₆O]⁺ +C₂H₄. Estimation of the enthalpy difference between the final state and the molecular ion supports the formation of a phenol-like structure for the [C₆H₆O]⁺ ion. The activation energy for backward reaction is compared with the mean kinetic energy release. Whether this is a concerted or non-concerted fragmentation is discussed.     

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.     

Fragmentation de la Méthyl-2 Indolizine sous Impact Electronique: perte de H˙ à partir de l'Ion Moléculaire; perte de HCN à partir de l'Ion [M?H˙]+

The origin of the hydrogen radical lost in the ionization chamber from the molecular ion of 2-methylindolizine has been studdied by examination of the spectra of four specifically deuterated species. Hydrogen loss involves preferentially a hydrogen from the methyl substituent but also one of the hydrogens of either ring, especially those of the 5-membered ring. The HCN elimination from the metastable [M? H^˙]⁺ ions was studied using a linked scan method; the results are consistent with loss of identity of all the hydrogen atoms of the precursor ion, which implies an extensive reorganization prior to fragmentation.     

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 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.     

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.     

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.     

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.     

Spectrométrie de Masse—IV: Fragmentation des Dicétones—ϵ

The mass spectra of ten symmetrical ?-diketones are reported and a number of fragmentation patterns are documented by deuterium labelling experiments. The McLafferty rearrangement involving one of the carbonyl groups is not an important fragmentation pathway although such a double rearrangement is observed for long-chained ?-diketones. Special attention has been given to the ions resulting from the loss of either a molecule of water or the neutral species C₂H₄ which may involve an electron-impact induced formation of cyclobutanol-type ions analogous to the photochemical Yang's reaction.     

Stabilité dans le méthanol et propriétés thermodynamiques de transfert des cryptates de certains cations de transition et de métaux lourds

Stability in Methanol and Thermodynamic Transfer Properties of the Cryptates of some Transition Cations and Heavy Metals The nature and stability of the macrocyclic and macrobicyclic complexes of Ag⁺, Cd²⁺, and Pb²⁺ (Mⁿ⁺) with 21, 22, 211, 221 and 222 in anhydrous methanol 0.05M in Et₄N⁺ClO^?₄, at 25° (see Scheme) have been determined by potentiometry and spectrophotometry. Binuclear complexes M₂L²ⁿ⁺ have been observed in all cases, besides the mononuclear MLⁿ⁺ complexes. The macrobicyclic 1:1 complexes MLⁿ⁺ exhibit an important ‘cryptate effect’ with Mⁿ⁺=Ag⁺, Pb²⁺ and Cd²⁺, but not with Cu²⁺ and Zn²⁺; their stability is in all cases maximum with 221. The applicability to our results of the recent extrathermodynamic hypothesis involving MLⁿ⁺ cryptates is examined.     

Spectrométrie de Masse d'Hétérocycles Azotés. VIII–Comportement sous l'Impact Electronique de Nitroarylazoles

The mass spectra of nitrophenylimidazoles and nitrophenylpyrazoles have been examined in order to establish whether neighbouring ortho-ortho′ substituents have an appreciable influence on the fragmentation patterns. For compounds having an ortho nitro group on the heterocycle, specific effects are observed. Isotope effects observed with deuterated derivatives confirm this and establish that in the case of o-nitroimidazoles the 2-H proton adjacent to both nitrogen atoms is involved in the loss of OH. Fragmentation of each compound is specific and study could eventually provide a satisfactory means for structure determination.     

Dérivés Alléniques du Phosphore. Influence de l'État de Coordination du Phosphore et de la Nature des Radicaux Liés au Phosphore sur les Signes de J(P?H)

The signs of the phosphorus-proton coupling constants in various allenic organophosphorus compounds have been determined by either analysis of the AB₂X spectra or double resonance. Probable absolute signs have been obtained by taking ³J(P? H) as positive. In allenic phosphine oxides, the following signs are obtained: ²J(P? H) +ve, ³J(P? H) +ve, ⁴J(P? H) ?ve, ⁵J(P? H) +ve and the ⁴J(P? H) coupling constant varies mostly with the inductive effect of the substituents bound to the phosphorus atom. In allenic phosphines, these sings are: ²J(P? H) +ve, ³J(P? H) +ve, ⁴J(P? H) ?ve and +ve and the ⁴J(P? H) coupling constant varies with both the inductive and resonance effects to the substituents. This coupling constant is negative except when the phosphorus atom is bound to groups which are electron-donating by resonance effects. These results are discussed in relation to the pπ? dπ bonding in phosphine.     

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 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.     

Etudes des sélénophènes mono et bisubstitués par Résonance Magnétique de 1H et de 13C

Proton and carbon magnetic resonance spectra of mono-and disubstituted selenophenes are investigated. The proton chemical shifts are discussed in terms of magnetic anisotropy and electric field effects of the substituents, with a view to studying the conformational equilibrium of the carbonyl group. π Electronic charges, computed by the PPP method, are correlated with the proton and carbon chemical shifts. The coupling constants between ¹³C and ¹H (1, 2 or 3 bonds) and ¹³C? ⁷⁷Se are shown to be good structural parameters and a set of substituent additivity constants is calculated.     

Application de la Résonance Magnétique de l'Azote 15 à l'Etude de la Délocalisation Electronique dans les Anilines,Aminopyridines et Enamines

¹⁵N spectroscopy at natural abundance has been applied to the study of electronic delocalization in the N? C bond of a series of substituted anilines. The relationships which offer a good way for evaluating the extent of electronic delocalization from ¹⁵N chemical shift data in anilines have been extended to aminopyridines, aminopyrimidines and nucleosides. The results obtained for C? N bonds in the case of anilines and aliphatic enamines are consistent with those concerning amides and analogous compounds. The validity of ΔG^≠-δ¹⁵N relationships for predicting π delocalization is discussed in terms of the relative contribution of δ- or π-density and non-bonded atom interactions to the total barrier height.     

Étude spectrophotométrique UV. de solutions diluées de chromate dans l'acide sulfurique concentré

Dilute solutions ( < 1· 10^?4M ) of CrO₄K₂ in concentrated sulfuric acid, were investigated spectrophotometrically. Spectral, kinetic and equilibrium studies confirm the instability of Cr^VI species and their conversion to Cr^V complexes, as proposed by MISHRA & SYMONS . Reaction mechanisms are proposed.     

Dérivés Alléniques de l'Étain,du Plomb et du Mercure. Signes Relatifs des Constantes de Couplage Métal-Proton á Travers Deux et Quatre Liaisons

Satellites corresponding to metal-proton coupling constants through two and four bonds are observed in PMR spectra of Pb, Sn and Hg allenic derivatives. The relative signs of these coupling constants are deduced from analysis of the satellite spectra: ²J(X? H) and ⁴J(X? H) are of opposite signs for X = ²⁰⁷Pb, ¹¹⁹Sn, ¹¹⁷Sn and of same sign for X = ¹⁹⁹Hg. Probable absolute signs of reduced coupling constants are discussed in relation to published data: ²K(X? C? H) is probably positive for X = ²⁰⁷Pb, ¹¹⁹Sn, ¹¹⁷Sn and ¹⁹⁹Hg. ⁴K(X? C?C?C? H) is probably negative for X = ²⁰⁷Pb, ¹¹⁹Sn, ¹¹⁷Sn and positive for X = ¹⁹⁹Hg.     

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.