2014 La première observation du signal de résonance magnétique nucléaire de l'isotope 235 de l'uranium est présentée. Elle a été effectuée sur l'hexafluorure d'uranium pur, à l'état liquide à 380 K. Le rapport gyromagnétique mesuré est égal à | 03B3(235U) | = 492,6 ± 0,2 rad.s-1 G-1. Abstract. 2014 The first observation of the nuclear magnetic resonance of the uranium 235 is reported. It has been performed on pure liquid uranium hexafluoride at 380 K. The measured magnetogyric ratio is | 03B3(235U) | = 492.6 ± 0.2 rad.s-1 G-1.

The γ‐ray‐induced postpolymerization of acrylonitrile and methyl methacrylate adsorbed on Linde zeolite 13X irradiated at 77°K has been studied between 303 and 343°K as a function of the amount of adsorbed monomer and of the irradiation dose. The change in the nature and the concentration of free radical with temperature and duration of the postpolymerization was followed by the ESR method, whereas the formation of polymer was monitored continuously by the decay of the 1H‐NMR absorption line of the monomer under high‐resolution conditions. It was found that the overall postpolymerization kinetics may be accounted for by assuming an exponential decay of radical propagation and recombination reactions with chain length. The tacticity of the polymer recovered by destroying the matrix in hydrofluoric acid was determined by 13C‐NMR. The probability of isotactic addition of AN and MMA is larger than in the radical polymerization in solution owing likely to the association of adsorbed monomer molecules in pairs preforming an isotactic diad.

Abstract-I3C n.m.r. spectra are reported for 1,3-indandione, phthalic anhydride, thiophthalic anhydride, and phthalimide in chloroform-d solution. The 13C chemical shifts have also been calculated by means of Pople's perturbation theory using CNDO/S wave functions; the agreement between theoretical and experimental values is improved when an empirical charge-dependent term is added to the calculated diamagnetic and paramagneitc contributions.As PART of a study on heterodicarbonyl compounds by spectroscopic and theoretical methods,lS2 we have measured the 13C n.m.r. spectra and performed quantummechanical calculations, based on the independentelectron MO theory of P~p l e ,~ for phthalic anhydride (l), thiophthalic anhydride (2), phthalimide (3) and their carbocyclic analogue 1,3-indandione (4). n EXPERIMENTAL Phthalic anhydride, phthalimide and 1,3-indandione were commercially available materials. Thiophthalic anhydride was synthesized as described in the literatui-e.4The I3C n.m.r. spectra were measured on a Varian XL-100 12-WG spectrometer operating in the pulsed Fourier transform mode at 25.15 MHz with D heteronuclear lock; proton noise decoupling was performed through the Gyrocode system at 100 MHz. Measurements were made in 10 mm sample tubes containing 0.5 M solutions of the compounds (with the exception of phthalimide, sparingly soluble, of which a saturated solution was examined), in CDCI, with TMS (c. 1 vol. "/u) as internal reference. As an example, the 13C FT n.m.r. spectrum of 1,3-indandione (4) is shown in Fig. 1. Spectral analysisThe carbonyl signal was readily identified from its low field position. The signal of the quaternary carbon C-2 was distinguished from the resonance of C-4 with the help of the splitting pattern observed in the C-H coupled spectrum. Assignment of the highest field aromatic resonance to C-3 is in agreement with the data available for an N-derivative of phthalimide5 and for the *Author to whom correspondence should be addressed. Table 1.The most striking aspect of the carbon resonances in this series of compounds concerns the spread of the carbony1 chemical shifts. This follows the trend 0 < NH < S < CH, and is as large as 34 ppm.The current qualitative interpretation of the downfield shift of carbonyl signals from TMS invokes the polarity of the carbonyl bond,^ while the scatter of the chemical shift values is accounted for in terms of factors affecting the bond polarity.8 On this basis, assuming other effects being equal, the carbonyl shifts of compounds 1-4 should be expected to increase with decreasing electron acceptor power of the X atom, since withdrawal of electron charge from the carbonyl oxygen towards the X atom is expected to decrease the carbonyl r-bond polarity. This argument implies the trend shown by the measured shifts. In addition, the differences in electronegativity as calculated by D e~a r ,~ O(4-8 eV), N(4.2), S(2-5) and C(2.5), are fairly well reflected in the chemical shifts.Although a direct correlation between the carbonyl resonance and the n -> r* ...

In order to investigate the influence of solute size on some thermodynamic parameters of transfer of hydrophobic solutes from light to heavy water, we have measured the partial molal volume and partial molal heat capacity of sodium iert-butylcarboxylate and sodium adamantanecarboxylate in H20 and D20 at 25 °C. Some XH NMR and Raman, measurements have also been done. They show that potassium adamantanecarboxylate is a structure breaker (relative to potassium tert-butylcarboxylate) with a molal structural + 4°. This substantiates the idea that an increase in size of a compact hydrophobic solute may drastically change the solute influence on water structure.

Abstract-In order to define the influence of an allenic type conjugation, the NMR spectra of vinylallene and of some of its methyl derivatives are analysed The signs of the coupling constants are also determined. These compounds are characterised by a planar s-trans structure of the two noncumulated double bonds. A discussion of the parameters, and especially of the methyl replacement effects, evidences the importance of the x type contributions. The theoretical calculations of the coupling constants by the methods of finite perturbation CNDO and l N D O corroborate this interpretation.