Michel Petraud

Moisture content and extractive materials in maritime pine wood by low field 1H NMR

Summary The low field 1H NMR relaxometry technique has been shown to be effective in determining the qualitative and quantitative moisture content and the water state distribution in maritime pine wood (Pinus pinaster Ait). Further investigations on extractive materials in resin-rich samples evinced the presence of oleoresin components, which may disturb adhesion on pine wood boards.

Chemical reaction of maritime pine sapwood (Pinus pinaster Soland) with alkoxysilane molecules: A study of chemical pathways

Abstract The chemical modification of maritime pine sapwood (Pinus pinaster) with alkoxysilanes was studied according to three different pathways: carbamoylation with 3-isocyanatopropyltriethoxysilane, etherification with 3-glycidoxypropyltrimethoxysilane and alcoholysis of n-propyltrimethoxysilane. Grafting was confirmed by weight percent gain calculations (WPG), infrared spectroscopy (FTIR) as well as 13C and 29Si NMR CP MAS analysis. Signals of the grafted groups in the different spectra were assigned and the reactivity of the trialkoxysilane moieties towards wood was discussed. Experiments with model wood blocks showed that the reactions investigated occurred within the wood cell walls. Grafted chemicals were found to be relatively stable with regard to water leaching but only slight dimensional stabilisation was noted after treatment.

Regio- and stereoselective addition of sterically hindered silylboranes to terminal alkynes

Abstract Novel stable organosilylboranes possessing dimesityl groups attached to boron were synthesised. They gave an addition reaction with terminal acetylenic hydrocarbons in the presence of a transition metal complex. Thus, (diphenylmethylsilyl)dimesitylborane and (diphenyl-tert-butylsilyl)dimesitylborane reacted in good yields with phenylacetylene and alk-1-ynes in the presence of Pd2(dba)3(etpo)2 as a catalyst. The structures of the products were determined by NMR spectroscopy using INEPT techniques coupled to computational simulation. Various heteronuclear coupling constants J 13 C − H and J 29 Si − H were determined for the first time in this series. The results showed that the dimesitylboryl group added to the terminal acetylenic carbon atom and the organosilyl group to the internal carbon atom, according to a regio- and stereoselective syn-addition.

Interet de la deuteriation des molecules organostanniques en RMN de 119Sn : II. Relation de type karplus pour 3J(SnD) et stereochimie de deuteriostannation de quelques hydrocarbures ethyleniques

Abstract Whenever selective deuterium labelling is easily performed a new proficiency is given to FT 119 Sn NMR by the determination of the angular dependence of 3 J (SnD). Using model molecules with structures being checked by other methods, the angular dependence of 3 J (SnD) has been shown to follow a Karplus-like relationship. Illustrative examples for the qualitative and quantitative analysis of diastereoisomeric organotin compounds are described. This method allows for instance, a fast and convenient determination of the stereochemistry of alkene deutero- and hydro-stannations.

Time-domain 1H NMR characterization of the liquid phase in greenwood

Abstract The time domain of 1H NMR spectroscopy allows straightforward editing of the T 2 relaxation profiles in maritime pine wood. A new method from the Carr-Purcell-Meiboom-Gill sequence is proposed to measure the amount and distribution of water in wood, as well as the location of major dissolved organic materials. A general calibration model giving reliable and precise identification of these parameters is described. The method presented for editing T 2 relaxation profiles (obtained by the Contin program) may be helpful in solving practical drying and gluing problems in the wood industry. It can be used for monitoring chemical modifications of wood fibers involved in the design of wood composite materials.

Interet de la deuteriation des molecules organostanniques en rmn de 119Sn : I. Acces aux constantes de couplage nJ(SnD) et application a l'etude structurale de vinyl et d'allyletains☆

Abstract The selective deuteration of organotin compounds gives FT 119 Sn NMR a new proficiency, since it allows direct access to n J (SnD) coupling constants. Usually n J (SnD) is easily apparent for n  1, 2, 3 and sometimes 4 (allyltin compounds). This criterion has been successfully applied for qualitative and subsequently quantitative analysis of vinyltin and allyltin compounds. In the first series, the stereochemistry of alkyne deuterostannation has been easily explored, the assignments of configurations being made directly from 3 J (SnD) on the basis of 3 J (SnD) trans > 3 J (SnD) cis . In the second series, the method appears to be the best tool for simultaneous study of regiochemistry and stereochemistry in the substitution of 3-deutero-5-methyl-2-cyclohexenyl toluene sulphonates by trialkylstannyl anions. The choice between regioisomers was made on the basis of 2 J (SnD) >- 4 J (SnD). A further aspect of this work is the observation of isotopic effects on 119 Sn chemical shifts which were tentatively rationalized considering inductive, steric or hyperconjugative contribution of deuterium.

Synthese et etude par resonance magnetique nucleaire du carbone 13 et de l'etain 119 d'une serie de triorganostannyl-2 butanes

Abstract Optically active triorgano-2-stannylbutanes have been synthetized by different methods, one being the direct substitution of optically active s-butyl halides with triorganostannyl alkali metals. This route involves a complete or partial inversion of configuration at the chiral carbon atom. Carbon-13 and tin-119 NMR data are reported as support for the identification of eight triorgano-2-stannylbutanes. The special case of tetra(2-butyl)tin, with four identical chiral centres has been examined.

SYNTHESIS AND CHEMICAL PROPERTIES OF 1,3-DICHLORO-1,3-DIHYDRIDODISILAZANES

Abstract A trans-silylation route to 1,3-dichloro-l,3-dihydridodisilazanes, a novel class of polyfunctional disilazane, is described. Thus, heating hexamethyl- or heptamethyl-disilazane under reflux in the presence of an excess of dichlorohydrogenosilane R 1 SiHCl 2 , led to compounds of formula (R 1 ClHSi) 2 NR 2 (R 1 = Me, Et, Vi or Ph and R 2 = H; R 1 = Me and R 2 = Me) in high yield. The exchange of chlorinated organosilicon moieties was strongly facilited by a catalytic amount of ( π Bu 4 N)F. Interpretation of the results and a few chemical properties of these novel disilazanes are reported.

Détermination de structures au moyen de la RMNn du 29Si: Transfert sélectif de population avec les méthylchlorodisilylméthanes

Abstract The selective population transfer (SPT) technique has been applied to 29 Si NMR of the complete series of methylchlorodisilylmethanes, several of which are new compounds. A great enhancement of the signals was observed and unambiguous assignments based on the determination of 2 J (SiH) coupling constants could be made. The first example of this type is presented.

A new preparation of hexaalkylditins. 119Sn NMR and chromatographic data on linear polytins

Abstract The reaction of triorganotin oxides and formic acid provides a good route to ditin derivatives. Several new linear polytin compounds have been isolated, and the vicinal and long range 119 Sn 119 Sn coupling constants determined. A linear relationship has been demonstrated between the logarithm of the HPLC retention time and the number of tin atoms in the compounds.