Sur la theorie quantique des equations de hartree–fock dependant du temps. IV. Expression matricielle du tenseur d'hyperpolarisabilité

Following a paper drawing up a matrix form of the time-dependent Hartree–Fock equations which allow the calculation of the nth harmonic generation, we establish the matrix form of the hyperpolarizability tensor. In case of linear polarization, we show that, if the ground-state orbitals are real, so are the perturbed ones. This involves an easy expression of the hyperpolarizability tensor.     

Structures électroniques du fluorocyclohexane et du gem-difluorocyclohexane

CNDO/2 calculations were performed on cyclohexane, cyclohexyl fluoride and 1,1-difluorocyclohexane. The electronic structure is discussed and compared with experimental data.     

Peroxydation du dihydro-2,3 4H pyranne et du dihydro-2,3 furanne. Etude de réactivités

Free radical reactions of unsaturated O-heterocycles with t-butyl hydroperoxide in the presence of cuprous salt gives peroxides. Their analysis leads to the determination of reactivities in H-abstraction. Allylic hydrogen is ten times more reactive than hydrogen in the α position of the heteroatom.     

Préparation du cyclohexadiène-1,4 à partir du benzène par voie organosilicique

3,6-Bis(trimethylsilyl)-1,4-cyclohexadiene, obtained from direct disilylation of benzene in an inert atmosphere, is hydrolysed at 0–5° in a strongly basic medium to 1,4-cyclohexadiene.     

Sur la synthèse du pollinastanol à partir du cycloartanol

The partial synthesis of pollinastanol (14) from cycloartanol (3) is reported. The transformation proceeds through the methylenic intermediate 12; the ring enlargement with cyanogen azide affords pollinastanone (13) further reduced to 14, The 4-keto isomer of pollinastanone (17) as well as a series of 5-β isomeric compounds are also described.     

Photooxydation du polyethylene. I. Cinetique de photooxydation du PEbd

The kinetics of photooxidation of ldPE films are characterized by the superposition of two phenomena: the first, corresponding to an exponential increase of CO concentration with time, is observed when oxygen diffusion controls the kinetics: the second, corresponding to a linear increase of [CO] with time and higher activation energy, becomes predominant in degraded samples in which [CO] ? 100 cm^?1. We suppose that the modifications of morphology following chain breaking in the amorphous phase favours oxygen access to the internal zones of the sample. Therefore, O₂ diffusion is no longer the rate determining process and we can observe the change of kinetic parameters. The disappearance of the vinylidene groups can be due to an attack by the alkoxyl macroradicals giving cross-linking. The rate of appearance of vinyl groups is temperature independent. At present, no interpretation of this result can be made.     

Structure du propyne par RMN en phase nématique. Utilisation des satellites du carbone-13

The proton NMR spectrum and carbon-13 satellites of partially oriented propyne give the complete structure of this molecule. Agreement with microwave results is excellent.     

Synthése d'héterocycles. XX. Reaction du malononitrile avec quelques cinnamonitriles

Reaction of cinnamonitriles with malononitrile, in methanolmethoxide, yield dihydropyridines, which by aromatisation give pyridines. Pyridine is directly obtained when p-nitrocinnamonitrile is used     

Utilisation d'ylides du phosphore en chimie des sucres. XII Dérivés du D-arabino-hexène-1-tétrol-3,4,5,6

The preparation of several kinds of derivatives of 1-substituted D -arabinc-hex-1-ene-3,4,5,6-tetrols is described. Some of these compounds, having a ‘pseudo-formyl’ group (? CH?CHCN, ? CH?CHSO₂CH₃) are ‘pseudo-aldehydo-sugars’. Their ability to react as aldehydo-sugars was examined in light of their ¹³C-NMR. spectra which provide information on their electron density at C(1) and C(2).     

Diazoalcanephosphonates. Etude par RMN du proton de la configuration de Δ1-pyrazolines dérivées du norbornadiène

The NMR spectra of eleven pyrazolines 1 to 11 derived from norbornadiene are interpreted and discussed. The configurations are deduced from the vicinal P?C?C?H₁₀ coupling: this is ～20 Hz in the anti derivatives and ～6·0 Hz in their syn epimers. The long-range P,H₉ coupling is stereospecific, being maximum for a syn configuration.     

La Vitamine B6 et ses Dérivés. I—Attribution des Spectres de Résonance 13C du Pyridoxol,du Pyridoxal et du Phosphate de Pyridoxal. Etude de la Protonation

The existence of two potential sites for protonation in the molecules pyridoxol and pyridoxal produces characteristic effects in their ¹³C nuclear magnetic resonance spectra. The analysis of these effects permits both the confirmation of assignments proposed by others and the establishment of the nature of the species existing in solution as a function of the pH. In particular it appears that, at pH values in the neighbourhood of 7, both substances exist essentially as zwitterions, pyridoxal adopting the hemiacetal form.     

Un nouvel hétérocycle telluré: le benzisotellurazole-1,2. 2. Structure cristalline et moléculaire du benzisoselenazole-1,2 et du benzisotellurazole-1,2

Anomalous physical properties (solubility and melting point) of 1,2-benzisotellurazole are explained by very short intermolecufar Te…N bonds (2.4 Å) found in the crystal structure. Such bonds are not present in the crystal structure of 1,2-benzisoselenazole and the physical properties are those expected.     

Cerimetrie en milieu nitrique. application au dosage du fer,de l'uranium et du plutonium

A method is described for titrimetric determination of iron, uranium or plutonium in nitric acid media. The element is reduced with titanium(III) solution in presence of sulfamic acid, and titrated with cerium(IV) solution. Precautions normally taken for nitric acid media are unnecessary. The method is rapid and precise and is readily applicable to determinations of plutonium or irradiated uranium.