Synthesis and experimental study of through-space hydrogen-fluorine and carbon-fluorine spin-spin coupling in 4,5-substituted 1-acetyl-8-fluoronaphthalenes

The synthesis and NMR study (1H, 13C, and 19F) of a complete series of 4,5-substituted 1-acetyl-8-fluoronaphthalenes are reported. This data revealed a 6J(H,F) and a 5J(C,F) through space coupling between the fluorine and the methyl on the acetyl group (1H and 13C). The magnitude of this coupling constant changes depending on the nature of the substituent at C-4, the internuclear distance, and the solvent.     

Twist mode in spherical alkali metal clusters

A remarkable orbital quadrupole magnetic resonance, so-called twist mode, is predicted in alkali metal clusters where it is represented by Ipi = 2(-) low-energy excitations of valence electrons with strong M2 transitions to the ground state. We treat the twist by both macroscopic and microscopic ways. In the latter case, the shell structure of clusters is fully exploited, which is crucial for the considered size region ( 8相似文献   

Numerical and experimental analysis of the plasma in the synthesis of polyaniline

A numerical and experimental study of the plasma variables in the synthesis of polyaniline in radio‐frequency (RF) glow discharges is presented. The plasma variables were measured on the basis of data collected by electrostatic Langmuir probes placed along the reactor. The results showed the distribution of the electric potential and the electronic energy and density during the polymerization reactions. The region with the lowest energy was the zone adjoining the grounded electrode, whereas the maximum energy was located near the RF electrode. In the second zone, the energy was around twice that of the grounded zone, and both were beyond the typical atomic bonding energy found in most organic polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1501–1508, 2003     

Fluctuation induced diamagnetism in aluminum

The magnetic field and temperature dependence of the magnetization of bulk aluminum near the normal-superconductor transition has been measured. Due to the large amount of supercooling in one of the samples it was possible to extend the measurements well below the critical temperature. A comparison of the experimental results with theory is presented.     

Action of amines and carbonyl reagents on 3,5-diphenyl-4-pyrone and its thio analogue

Several N-substituted, 3,5-diphenyl-4-pyridones and 4-thiopyridones were obtained by the action of amines on 3,5,-diphenyl-4-pyrone and its thio analogue. With hydrazine hydrate, the products were 1-amino-3,5-diphenyl-4-pyridone and the corresponding thione. The spectral characteristics ol these pyridones were studied.     

Relativistic mean field approach to the scattering of antinucleons and nucleons by nuclei

A realistic mean field approach based on the Walecka theory for nuclear matter is used to derive the optical potential for nucleon and antinucleon-nucleus systems. The total and reaction cross sections are calculated in the WKB approximation for different nuclei ranging from carbon to lead and for incident energies between 0.1 and 2 GeV.     

Preuve d'une conjecture de Brieskorn

In this paper we prove the following conjecture of Brieskorn: The complex of (holomorphic) differential forms of an isolated hypersurface singularity of dimension n>1 is exact in degree n–1.     

Mechanisms of nucleophilic substitution reactions of methylated hydroxylamines with bis(2,4-dinitrophenyl)phosphate. Mass spectrometric identification of key intermediates

Mono- and dimethylation of hydroxylamine on nitrogen does not significantly affect rates of initial attack of NHMeOH and NMe(2)OH on bis(2,4-dinitrophenyl)phosphate (BDNPP), which is largely by oxygen phosphorylation. O-Methylation, however, blocks this reaction and NH(2)OMe then slowly reacts with BDNPP via N-attack at phosphorus and at the aryl group. With NHMeOH, the initial product of O-attack at phosphorus reacts further, either by reaction with a second NHMeOH or by a spontaneous shift of NHMe to the aryl group via a transient cyclic intermediate. There is a minor N-attack of NHMeOH on BDNPP in an S(N)2(Ar) reaction. Reactions occurring via N-attack are blocked by N-dimethylation, and reaction of NMe(2)OH with BDNPP occurs via O-attack, generating a long-lived product. Reaction mechanisms have been probed, and intermediates identified, by using both NMR and MS spectroscopy, with the novel interception of key reaction intermediates in the course of reaction by electrospray ionization mass and tandem mass spectrometry.