Theorie des Orbitals Moleculaires: Recherche d'une Base STO Homogene pour les Atomes Alcalins et Leur Serie Isoelectronique

A method of direct treatment of valence electrons is proposed for the various ²S, ²P,²D, ²F states of the lithium, sodium, and potassium atoms and the corresponding isoelectronic ions. The function describing the outer electron, which is orthogonal to the wave functions of the electrons in the core, is given as a linear combination of generalized Laguerre functions, with effective charges Q = 1, 2 …? equal to the charges of the core. A simpler analytical STO function, with non-integer principal quantum number n is then proposed.     

I. Etude de l'Influence de la Nature et de l'Orientation d'un Substituant sur les Constantes de Couplage en Série Tertiobutyl-4 Cyclohexanonique par RMN à Haut Champ

The 250 MHz proton spectra of six α-halogeno-4-tert-butylcyclohexanones have been recorded and the dependence of the coupling constants upon the nature, the position, the orientation and the number of substituents (C?O, Cl, t-Bu) has been examined. The results obtained are interpreted in terms of geometrical deformation or substituent effects.     

Etude RMN 13C d'un Dérivé Uniformément Enrichi en 13C. Signe des Valeurs des Constantes de Couplage Observées

The ¹³C NMR parameters of 3-O-acetyl-1,2:5,6-di-O-isopropylidène-α-D-[U-¹³C] glucofuranose, used as a sample for analysis in double labelling biosynthetic experiments, have been measured. Homonuclear double resonance experiments ¹³C? {¹³C} at 62.8 MHz have permitted the determination of all the ¹³C? ¹³C coupling constants. By theoretical computation of spectra, in connection with the second order effects existing at 25.2 MHz and 15.08 MHz, the sign of the coupling constants has been determined. The theoretical computation of spectra took into account all the isotopomers and was calculated with the help of a program (adapted from the LAOCOON program) allowing for the weighted addition of the spectra.     

Couplage des sulfones allyliques avec des reactifs de grignard en presence de cuivre synthese d'olefines

A convenient synthesis of di- and trisubstituted olefins using the coupling of Grignard reagents with allylic sulphones in the presence of copper II acetylacetonate is reported. The influence of sulphone, Grignard reagent and solvent on the regio- and stereoselectivity is discussed.     

Equation de Karplus et l'Hybridation du Carbone. Correlation de la Constante de Couplage Vicinale 3J(Hi,Hj) et la Somme de Constantes de Couplages 1J(C,H)

The vicinal coupling constant ¹H? ¹H exhibits a marked hybridization dependence. The coupling constants ¹³C? ¹H could be used to correlate the Karplus type equation for calculation of ³J(Hi, Hj). The correction term to this equation is proposed.     

Etude de la Fragmentation en Spectrographie de Masse de Spiropyrannes Benzodithioliques. Influence de la Position et de la Nature des Substituants

The mass spectra of 12 benzodithiolic spiropyrans are reported. Their fragmentation pathways have been determined by exact mass and metastable transition measurements. The nature of the fragmentation is strongly dependent upon the position and nature of the substituents. A comparison is made with their photo and thermochemical decompositions.     

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.     

Spectrometrie de Masse des Acetates de la Serie Bicyclo-(2.2.1) heptane. Elimination de Cetene et Fragmentation Type

Elimination of ketene is shown to occur through a four centre mechanism with the acetates of the bicyclo[2.2.1] series. A typical fragmentation, related to the rearrangements of carbonium ions, is induced by an unsaturation at position 3.     

Etude en Serie as-Triazine. XIX—Fragmentations Principales de s-Triazolo-as-Triazinones en Spectrometrie de Masse

The mass spectra of s-triazolo[4,3-b]-, -[3,4-c]- and -[3,2-c]as-triazine-7-ones and their N-methyl derivatives are described. The elucidation of fragmentation pathways is made easy by observation of the changes in m/e values on changing position of the methyl substitution. In all cases a triazine ring fragmentation with initial loss of CO, RCN or RCNCO was observed. This result is characteristic of the different isomeric structures of triazolotriazine-7-ones. The comparison of the spectra of these compounds with those of their N-methyl derivatives shows the occurence of a tautomeric equilibrium, as found from u.v. spectroscopy.     

Analyse en Spectrometrie de Masse de Derives Fluores en Serie Pyrimidine et Triazine

We have synthesised all the fluorinated derivatives of perchloropyrimidine, trichloro-2,4,6-pyrimidine and perchloro-s-triazine. Fluorine n.m.r. analysis, associated with gas chromatography coupled with mass spectrometry, allowed separation and identification of the products. The behaviour of these compounds under electron-impact is presented and discussed here.     

Etude de la repartition de l'uranium dans les roches par la methode des traces de fission. Application a l'echantillonage en vue du dosage de l'uranium

The distribution of uranium in two different rock species: basalt from the Fangataufa atoll (located in Polynesia) and granit from the Hoggar mountains (located in Sahara) was studied by the fission track method. The two distributions observed appear quite different: uranium is uniformly distributed in the vitrous part of the basalt while in granit it is located on the intergranular joints. Applying the sampling model proposed by A. D. WILSON to the observed distributions of uranium, the weight of the analytical sample corresponding to a required sampling error can be estimated. Results show that representative sample weights of the bulk powdered material, as usually obtained by milling, are about some tenths of milligrams for basalt and more than the grams for granit (for uranium analysis). So, in trace element analysis, the sampling error could be more important than the analytical one. This fact could explain the relatively poor accuracy of trace determinations in rock samples (including the reference samples).      

Etude en Spectrometrie de Masses des Fragmentations de Derives de la Triazine-1,2,4

The mass spectra of 49 1,2,4-triazines with oxo, thioxo, methoxy and methylmercapto groups in the 3 and 5 positions are reported and analysed. Five distinct patterns have been observed upon electron impact but an initial loss of N₂ has not been identified. A tautomeric equilibrium has been shown to occur in the vapour phase from some fragmentation pathways.     

Tetrahydro anthraquinones disubstituees en - 1,5: etude de la regioselectivite de la reaction de diels-alder entre des naphtoquinones et des dienes attracteurs.

Diels-Alder reaction of - 2,4 pentadienoïc acid and its methyl ester (electron with-drawing) dienes with juglone and its derivatives is described. High regioselectivity is observed, the adducts have a “head-to-tail” geometry.     

Application de la methode de dosage en surface a l'aide des reactions nucleaires pour l'evaluation de l'interference surface-masse

Résumé Dans un programme de recherche visant à étudier les différentes méthodes de dosage de l'oxygène dans les métaux non ferreux, nous avons été amenés à examiner l'influence de l'oxygène de surface sur la détermination de l'oxygène dans la masse. Cette analyse de la surface a été réalisée en utilisant les réactions nucléaires induites par des particules chargées de faible énergie obtenues à l'aide d'un accélérateur Van de Graaff de 2 Mev.     

Etude de la Fragmentation des bis Alkylthio-3,5 Isothiazoles en Spectrometrie de Masse

The study of the fragmentation schemes of twenty-six 3,5-Bis(alkylthio)-isothiazoles allows us to show new fragmentation modes in the isothiazole series. Two important breakdowns could be distinguished in the case of 3,5-Bis(alkylthio)-isothiazoles, from examination of the data concerning the spectra of the deuteriated derivatives in each position concerning the loss of the mer-capto radical and of two atoms of sulphur, respectively. We have shown the specific effect of the thio-alkyl substituents in the cleavage process. A transposition mechanism of the molecular ion is considered to explain the two rival fragmentation schemes.     

Application de la chromatographie en phase gazeuse et de la spectrométrie de masse à la recherche des résidus de pendiméthaline dans les eaux

(Application of gas chromatography and mass spectrometry in analysis for pendimethaline residues in waters.)The extraction of the herbicide pendimethaline [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine from waters with benzene is described. The method is suitable for the determination of this herbicide at residue level, by capillary gas chromatography and its identification by mass spectrometry. The detection limit is 1 μl^?1 for a 1 l sample of water.     

Reaction d'oximation des cetones iv. : Constantes d'equilibre de formation des carbinolamines intermediaires : determination et effets de structure

The equilibrium constants of formation, K₁, of carbinolamines resulting from the addition of hydroxylamine to 19 ketones, - 5 aliphatic, 5 aromatic and 9 cyclanic -, have been measured at 25° C in water/methanol 60/40 v/v. A general method of determination of K₁, is described.The variations of the equilibrium constant are discussed in terms of torsional and non-bonding steric effects which are the main factors of reactivity for saturated ketones.     

Analyse en coordonnees normales des vibrations de la 4-nitropyridine N-oxyde

A 51-parameter force field is established for the vibrations of the 4-nitropyridine N-oxide (NPO) and the 4-nitropyridine-d₄ N-oxide (NPO-d₄) molecules. The mean error between the 72 observed and calculated frequencies is 4.8 cm⁻¹ for the in-plane vibrations and 2.1 cm⁻¹ for the out-of-plane vibrations. The NCA calculations confirm our previous assignments for the NPO spectra, but four frequencies were permuted for NPO-d₄. The force field calculations were extended to fit the vibrational frequencies of NPO in solution in CCl₄, MeOH and H₂O. The fact that a donor solvent favours one resonant form of NPO is clearly demonstrated by the variations of five force constants.     

Utilisation du calcul des modes normaux de vibration pour la détermination de la conformation de la glycylglycine et de la triglycine en solution aqueuse

The valence force field of α-glycylglycine was applied to different G matrices calculated for several values of the dihedral angles ψ₁, φ₂ and ψ₂. The relations v_i = ?(ψ_i,φ_i) obtained for different isotopic species were compared with the experimental frequencies of the aqueous solution thereby giving the absolute value of the angles. A complementary study by means of depolarised light scattering led to the determination of their sign. These relations were then used in the conformational analysis of triglycine in aqueous solution. The conformation of glycylglycine differs strongly in aqueous solution from that in the solid state, especially concerning the relative positions of the peptide and carboxylic group (φ₂ = ?70° and ?160°). For triglycine, we showed the existence of a chelated ring “C₇” similar to that observed for the acetylated dipeptides.