Fragmentations de quelques derives thiophosphores sous l'impact electronique. I—migration de groupes phenyles et methyles dans les derives du diphenylthiophosphorane

The localised radical or charge site formalism in substituted diphenylthionophosphoranes Ph₂P(S)R (R = phenyl, methyl, benzyl, methylthiomethyl, phenacyl, amino and N-benzylideneamino) allowed the elucidation of their electron-impact-induced fragmentation patterns. The atomic composition of the fragments was determined by precise mass measurements. Fragmentation patterns are proposed which are consistent with the presence of several metastable peaks. These patterns for phenyl, methyl, phenacyl and amino diphenylthionophosphoranes are characterised by a significant migration of the phenyl and methyl group from phosphorus to sulphur. Different patterns are favoured in benzyl, methylthiomethyl and N-benzylideneamino diphenylthionophosphoranes by elimination of very stable species.     

Spectrometrie de masse d'heterocycles azotes. IV—comportement sous l'impact electronique d'iodures de pyrazoliniums-2

The behaviour of 2-pyrazolinium iodides in mass spectroscopy has been investigated. The simultaneous fragmentation of four neutral molecules has been observed, which have been formed by substitution reactions of the iodide anion on the N-1 substituents. Thus, these reactions which have been shown to occur in protic solvents, also occur in the gaseous phase and under electron-impact.     

Fragmentation de Triazoles sous l'Impact Electronique–III Benzotriazole et Derives Alkyles

The behaviour of benzotriazole and some alkyl derivatives upon electron-impact has been studied. Evidence for the exclusive presence of the 1H-benzotriazole tautomer in the gaseous phase is presented. The 2H-benzotriazole ‘molecular ion’ is generated from 2-ethylbenzotriazole by ethylene elimination; isomerisation into the 1H tautomer precedes the fragmentation (nitrogen loss). A ring expansion reaction is proposed for the [M – CH₃]⁺ ions of 1-ethyl- and 2-ethylbenzotriazoles.     

Sels de cobalticinium : II. Proprietes spectroscopiques et polarographiques de quelques derives du cobalticinium

The spectroscopic and polarographic behaviour of some cobalticinium derivatives have been studied. Due to their positive charge these compounds exhibit particular characteristics in comparison with ferrocene derivatives. They give two successive cathodic waves on a dropping mercury electrode. The first corresponds to the formation of cobaltocene whereas the second represents the reduction of the latter compound to give cobaltocene anion.     

Phosphates d'enols. XII—Etude en Spectrometrie de Masse de Derives Diethyliques et di-n-Butyliques

The mass spectrometric fragmentations of diethyl phosphates (1) and di-n-butyl phosphates (2) are influenced by the nature of the substituents R, R′ and R″ fixed on the double bond When R = H, the loss of ethylene or 1-butene is mainly observed. When R = CH₃, the double rearrangement process occurs with alkyl group participation of the enolic chain.     

Sur quelques méthodes de microdosage du soufre dans les composés organiques — Etude comparative et critique

Résumé Les auteurs rappellent et comparent quatre méthodes de minéralisation des composés organiques en vue d'y doser le soufre: ce sont la méthode de combustion oxhydrique, la combustion dans l'oxygène, soit en tube droit vide, soit en fiole du type «Schöniger» et la minéralisation réductrice en tube scellé par le potassium. Ils les associent aux méthodes de titrage des ions SO₄ ^2– ou S^2–.Leur étude leur permet de sélectionner parmi les méthodes décrites la minéralisation réductrice par le potassium associée au titrage iodométrique des ions S^2– comme la plus universelle et la plus sûre d'entre elles.Résumé Four methods of mineralization of organic compounds are recalled and compared with respect to determining sulfur in them; they are the oxyhydrogen combustion method, combustion in oxygen, in an empty tube, or in a flask of the Schöniger type, and the reductive mineralization in a sealed tube by potassium. They are combined with the titration methods for the SO₄ ^2– or S^2– ions. This study has enabled the authors to select the reductive method of mineralization by means of potassium followed by the iodometric titration of S^2– ions as the most general and most reliable among the various procedures.

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Zusammenfassung Die Verfasser berichten vergleichend über vier Methoden zur Mineralisierung organischer Verbindungen, deren Schwefelgehalt bestimmt werden soll, und zwar die Verbrennung in der Knallgasflamme, im Sauerstoffstrom im leeren Rohr, im Schönigerkolben und die reduktive Zerstörung mit Kalium im verschlossenen Röhrchen. Diese Methoden wurden mit der maßanalytischen Bestimmung des Sulfats bzw. Sulfids kombiniert. Daraus ergab sich, daß die Reduktion mit Kalium und die nachfolgende jodometrische Bestimmung des Sulfids am allgemeinsten anwendbar und am sichersten ist.

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A M. le ProfesseurJureek, D. Sc. à l'occasion de son 60ème anniversaire.     

Fragmentation d'azoles sous l'impact electronique. X—etude de rearrangements cycliques en serie alkylamino-1,2,4-triazole

In situ generation of the individual tautomers by fragmentation reactions in the mass spectrometer is shown to provide a means of studying rearrangements of the type involved in prototropic equilibria. C-aminotriazole was generated in different tautomeric forms by ethylene elimination from the N-ethyl compounds and the tautomers were shown to equilibrate prior to further fragmentation. Ethylene elimination was shown by characterising the energy partitioning associated with the metastable ion reactions to occur via a four centred transition state from two ethylamino-triazole isomers and via a five centred transition state from the third. These mechanistic conclusions were supported by characterising frequency factors through measurements of kinetic isotope effects. Propene elimination from the corresponding propylaminotriazoles was studied by analogous methods. Energy partitioning and kinetic isotope effect studies were in agreement with a stepwise elimination of propene, or with a five centred β-hydrogen transfer mechanism.     

Organocuivreux vinyliques : III. Carbonatation: Preparation stereospecifique d'acides α-ethyleniques et de quelques derives

Vinylcopper compounds are converted stereospecifically and almost quantitatively to the corresponding β,β-disubstituted α-ethylenic acids by carbonation. The influence of solvants and ligands in this insertion is discussed. Various functional groups are derived from these acids.     

Ionisation et Fragmentation en Spectrometrie de Masse. V—Appreciation de L'Energie D'Activation Pour des Fragmentations Competitives

A competitive kinetic shift has been demonstrated in the course of a molecular ion fragmentation leading to competitive cleavages. A method for the calculation of this ‘competitive kinetic shift’ is suggested.     

Dosage de l'oxygene dans l'uranium et ses composes par la methode au monochlorure de soufre

A sulfur monochloride method is proposed for the determination of oxygen in uranium compounds. Sulfur monochloride reacts with oxygenated compounds at temperatures depending upon their nature; the sulfur dioxide produced is titrated by iodometry, after the excess reagent has been eliminated by a selective adsorption-desorption process using activated charcoal. This method has been successfully applied to uranium oxides (UO₂, U₃O₈), to mixtures of uranium dioxide with uranium, uranium nitride, and uranium carbide, and to substituted carbides (UC_1-xO_x). The results are generally satisfactory for oxygen contents higher than 500 p.p.m. However, in the presence of free or combined carbon, this limit is considerably higher. A loss of oxygen as carbon monoxide is also possible, and a simultaneous determination of carbon monoxide must be carried out. The relative error is of the order of a few per cent.     

Synthese en serie encombree. preparation de l'acide ditertiobutyl-methylacetique-tBu2 MeCCOOH et de quelques composes cetoniques derives de cette structure

The synthesis of ^tBU₂MeCCOOH, which is among the most sterically hindered known acjds is described. Only Newman's sequence via ^tBU₂CO, ^tBu₂MeCOH, ^tBu₂CCH₂, _tBu₂CHCH₂OH, ^tBu₂CHCOOH, ^tBU₂CHCOCI and ^tBu₂CCO, which has been optimized in this work by a direct access to ^tBu₂CHCOOH, permits the preparation of ^tBu₂MeCCOOH. The condensation of the corresponding chloride with a Grignard reagent yields new highly-hindered ketones ^tBu₂MeCCOR which by alkylation give more substituted structures. The limitations of each method have been studied in this work.     

Transposition des Cycles Satures en Spectrometrie de Masse IV—Dioxolanes Derives de Cetones a Cycle Moyen et Grand

The fragmetation mechanism of cyclanone ethylene acetals in the medium ring and macrocyclic series has been re-investigated. The fragmentation pattern can be explained entirely on the basis of a new rearrangement, involving a ring contraction and hydrogen migrations, which have been checked by using deuterated compounds.     

Alkylation de quelques composés carbonylés par des groupes tertiaires. Utilisation de la réaction de friedel-crafts dans la synthèse d'ésters

t-Alkylation of carboxylic esters via their ketene alkyl trimethylsilyl acetals by the Friedal-Crafts reaction allows the synthesis of new highly hindered compounds. A new route using sodium amide in dimethoxyethane, for the preparation of trimethylsilylenol ethers of ketones, is described. The α-t-butylation of these compounds permits the synthesis of new crowded pentasubstituted ketones. The limits as well as the performance of the method have been studied.     

Insertion de so2 dans la liaison titane—carbone: I. Diastereotopie et diastereoisomerie engendrees par la presence d'un atome de soufre chiral dans les produits d'insertion

Sulfur dioxide insertion reactions in titanium—carbon bonds are studied with two types of titanocene complexes: Cp₂Ti(C₆F₅)R and CpCp′Ti(C₆F₅)R. The NMR spectra of the insertion products from the first type of complex are typical for O-sulfinated complexes having a chiral sulfur atom. Starting from the second type or complex two diastereoisomers have been detected (diastereoisomery Ti, S).     

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.     

Structure du reactif d'ivanov et de quelques organometalliques issus des derives phenylacetiques—I : Etude des solutions par rmn

Ivanov reagent add several analogous reagents (phenyl acetique serie) have been studied by NMR. In all the cases, an enolate-structure is revealed; no carbaneniate-species could be detected, even in very solvating solvents.     

Structure du reactif d'ivanov et de quelques organometalliques issus des derives phenylacetiques—II : Stereochimie de la condensation avec la t-butyl-4 cyclohex-anone

Ivanov reagent and some other analogous reagents (phenyl acetique serie) have been condensed with t-Bu-4 cyclohexanone in order to complete investigation of the reactive species. In all the cases, equatorial attack is highly predominant; it let suppose that enolate, detected by NMR, is the reactive species.     

Sels de Pyrylium. XVIII. Etude par RMN du Carbone-13 de Sels d'Aminopyrylium et des Barrières de Rotation dans quelques Cations N,N-Diméthylaminopyrylium

The C-2—N bond of 2-N,N-dimethylaminopyrylium cations has a partial π character due to the conjugation of the nitrogen lone-pair with the ring. The values of ΔG^≠, ΔH^≠, ΔS^≠ parameters related to the corresponding hindered rotation have been determined by ¹³C NMR total bandshape analysis. This conjugation decreases the electrophilic character of carbon C-4 so that the displacement of the alkoxy group is no longer possible. Such a hindered rotation also exists in 4-N,N-dimethylaminopyrylium cations and the corresponding ΔG^≠ parameters have been evaluated. Comparison of these two cationic species shows that hindered rotation around the C—N bond is larger in position 4 than in position 2. Furthermore, the barrier to internal rotation around the C-2? N bond decreases with increasing electron donating power of the substituent at position 4. ΔG^≠ values decreases from 19.1 kcal mol^?1 (79.9 kJ mol^?1) to 12.6 kcal mol^?1 (52.7 kJ mol^?1) according to the following sequence for the R-4 substituents: -C₆H₅, -CH₃, -OCH₃, -N(CH₃)₂.     

Méthode de marquage de groupes carboxyliques dans les peptides. Propriétés chromatographiques et autres,de peptide-p,p′-dimapa-anilides

Résumé Les auteurs décrivent une méthode efficate et les conditions (faibles valeurs de pH, milieu dioxane/eau (1∶2), carbodiimide hydrosoluble) de formation de peptides colorés par réaction de leur groupe carboxylique avec un colorant aminé (par exemple: 1(4-diméthylamino-1 phénylazo)-4-aminobenzène=p,p′-dimapa-aniline), sans polymérisation du peptide non-protégé. Quelques méthodes chromatographiques, faciles à mettre en oeuvre, pour l'isolement de peptide-p,p′-dimapa-anilides et quelques propriétés de ces nouveaux composés (peptides-C-colorés) sont présentées.

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Method for labelling carboxylic groups in peptides. Chromatographic and other properties of peptide-p,p′-dimapa-anilides

Summary The authors describe an effective method and the conditions (low pH values, dioxane/water (1∶2) media, watersoluble carbodiimide) for making coloured carboxylic peptides from amino-dye (i.e.: 1(4-dimethylamino-1 phenylazo)-4-aminobenzene=p,p′-dimapa-aniline), without polymerisation of unprotected peptide. Some easy chromatographic methods for isolation of peptide-p,p′-dimapa-anilides and some properties of these new compounds (C-dyed-peptides) are given.

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