Alain Bouchy

A self-consistent reaction field model of solvation using distributed multipoles. I. Energy and energy derivatives

The self-consistent reaction field model developed previously by the authors in the case of single center multipole expansion of the electronic structure of the solute has been extended to the case of a distributed multipole expansion. Three different expansions have been tested and two of them have proved to be rapidly convergent. The performances of the code are illustrated by the density functional theory treatment of few test systems: guanine, cytosine, and cytosine hydrated with one and three water molecules. A robust fast computer code has been tested to get the electronic structure, the electrostatic contribution to the solute-solvent free energy of interaction, and the optimized molecular geometry in solution.

Reactions of n-butenes on palladium films. Evidence for π-allylic species

The contact reactions of all three n-butenes have been investigated on palladium films in the presence of perdeuteropropene or deuterium, using jointly mass spectrometry and microwave spectroscopy.Conclusive evidence has been found for an allylic mechanism in exchange and double-bond migration.Part of the exchanged molecules result from dissociative vinylic-type adsorption and isomerization also takes place according to an associative Horiuti–Polanyi mechanism or by direct processes without deuterium incorporation. A proposal was made which correlates the various reaction mechanisms with various types of surface metal atoms, each having a different coordination number.

Microwave spectrum of the s-trans form of 3-pyridinecarbaldehyde

Abstract The microwave spectra of the ground state and one excited state of the ON s-trans form of 3-pyridinecarbaldehyde have been measured and assigned. The ground state rotational constants and dipole moment components are: A = 5417.8, B = 1583.289, C = 1225.389 (in MHz) and ¦μ a ¦ = 1.35, ¦μ b ¦ = 0.5 (in debye). The excited state most probably belongs to the C 3 C torsion, for which the vibrational frequency is estimated to be 135 ± 30 cm −1 .

Etude de la structure geometrique de la molecule de para-chloroaniline par spectroscopie microonde

Abstract The microwave spectra of the normal, mono and di N -deuterated species of para 35 Cl and 37 Cl aniline have been observed. The rotators associated with the two first states of the amino group inversion and with the three first states of the chlorine atom out of the plane vibration have been assigned. A geometrical structure has been calculated from the moments of inertia of all isotopic species in the ground state, the out of plane angle of the NH 2 group being 42.5°. The electronic interaction between the chlorine atom and the amino group has been pointed out.

INDUSTRIAL PHOTOCHEMISTRY. XXI: CHEMICAL, TRANSPORT AND REFRACTIVE INDEX EFFECTS IN SPACE-RESOLVED LASER PHOTOPOLYMERIZATION

Abstract Stereophotolithography involves surface-resolved photopolymerization induced by laser. The basic principle is to create object by a layer-by-layer system. In order to optimize the process show how we can change heat and mass transfer during the photopolymerization reactions. After a theoretical approach to the basic phenomena, a comparison between the experimental and expected results demonstrates that more elaborate modelling is required. Monte Carlo modelling shows the strong influence of the change in refractive index during the photopolymerization reaction on the space resolution, which induces some important limitations. In some cases, solutions are proposed.

Microwave spectra of meta-chloroaniline

Abstract The microwave spectra of the normal, NHD and ND 2 molecules of meta-chloroaniline for both isotopic species 35 Cl and 37 Cl have been studied. We have identified 12 rotators corresponding to the ground state (O + ) and the first excited vibrational state (O − ) associated with the inversion motion of amino group. The influence of the deuteration of the large amplitude motion of the amino group is estimated. The limiting geometries of the NH 2 and ND 2 meta-chloroaniline are proposed.

Microwave substitution structure of the amine group in meta-chloroaniline C6H4CINH2

Abstract Microwave spectra of amine-deuterated species of 3-35Cl-aniline, C6H4CINH2, have been observed. The two amino hydrogen atoms are found to be out of the plane of the aromatic ring, and appear to be farther out of the plane when the amine group is deuterated. It has also been shown that the Htrans, c coordinate (0.300 A) is larger than the cis one (0.281 A).

Microwave spectroscopy and nuclear magnetic resonance study of the molecular geometry of 2-fluorophenylisocyanate

Abstract Analysis of the microwave spectra of the vibrational ground state of 2-fluorophenyl-isocyanate in the gaseous state shows the existence of a single planar cis conformer. Rotational spectra of the excited torsional states out of the plane and spectra of in-plane vibrations have also been studied. MINDO III type theoretical calculations corroborate the experimental results. Similarly, the configuration of 2-fluorophenylisocyanate in the liquid phase has been studied by NMR using the chemical shift reagent, Eu(fod)3. Induced paramagnetic shifts have been measured on the 13C spectra, for different quantities of the reagent. The results clearly show a higher paramagnetic shift for the carbon bonded to the fluorine atom than for the other nuclei of the aromatic cycle (with the exception of the quaternary carbon), indicating the probable presence of the cis isomer.

Spectres de rotation des especes hexa- et octo-deuteriees de la molecule de cis-but-2-ene

Resume Les spectres de rotation de cis -2-3-H 2 - d 6 -but-2-ene et cis-d 8 -but-2-ene ont ete observes dans le domaine de frequence 18–40 GHz. La contribution de la rotation interne des toupies est negligeable. La validite de la barriere haute est confirmee en observant que tous les transitions de rotation sont des triplets symetriques. Les constantes de rotation rigides ont ete determinees precisement et la geometrie de la molecule cis -but-2-ene est discutee.

Industrial photochemistry XIII: determination of the most suitable irradiation conditions for molecular photoreactions

Abstract Each photoreaction is a special case with regard to the optimal use of light as a synthetic agent. For molecular photoreactions, we describe a simple method, based on a selective filtering principle, for the determination of both the maximum concentration of a desired product or the maximum benefit, which implies the definition of the optimal conditions for the phototransformation. The selective filtering methods developed always give a reduction in the reaction time and generally without too large a loss of selectivity. Using the proposed modelling procedure, if spectroscopic characteristics and kinetic data of any photoreaction are available, an a priori reaction course can be found and thus it is possible to determine whether or not the photoreaction is of industrial interest. Some examples of application are given to illustrate these principles.