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1.
The dipole moments of thirteen aryl styryl sulphides and eleven aryl styryl sulphones have been determined. Among them are
eightcis-trans isomeric pairs, four sulphides and four sulphones. The styryl group is found to conjugate with the sulphide function as an
electron-withdrawing group. The angles which the styrylthio and styrylsulphonyl groups make with their axes of rotation are
calculated. The observed dipole moments of the sulphides and sulphones are compared with the moments calculated by the vector
addition of group moments. The dipole moments ofcis aryl styryl sulphides and sulphones are found to be generally lower than those of theirtrans isomers. An explanation is offered attributing the cause to sterically enhanced styryl-sulphur conjugation in thecis isomers. 相似文献
2.
Julio Casado Albino Castro J. Ramón Leis Manuel Mosquera M. Elena Peña 《Monatshefte für Chemie / Chemical Monthly》1984,115(8-9):1047-1057
The kinetics of the nitrosation ofN-methylacetamide have been studied using spectrophotometry. Significant differences with respect to the mechanism of nitrosation of amines were observed: the absence of catalysis by halides, the existence of general basic catalysis by acetate and its chlorated derivatives obeyingBrønsted's law (with =0.49), and the primary isotopic effect (with a ratio of 7.9 between the rate constants for the elementary process in H2O and D2O). All this indicates that the slow step of the mechanism must be the transfer of a proton from the protonated nitrosamide to the reaction medium.
Kinetische Untersuchungen zur Bildung von N-Nitroso-Verbindungen, 10. Mitt.: Die Nitrosierung vonN-Methylacetamid und die Unterschiede in bezug auf die Nitrosierung von Aminen
Zusammenfassung Die Kinetik der Nitrosierung vonN-Methylacetamid wurde mittels Spektrophotometrie untersucht. Es wurden signifikante Unterschiede zum Mechanismus der Nitrosierung von Aminen beobachtet: die Abwesenheit einer Katalyse durch Halogenide, die Existenz einer generellen basischen Katalyse durch Acetat und dessen chlorierten Derivaten unter Übereinstimmung mit demBrønstedschen Gesetz (mit =0,49) und einem beobachtbaren Isotopeneffekt (mit einem Verhältnis von 7,9 zwischen den Geschwindigkeitskonstanten in H2O und D2O). All das zeigt an, daß der geschwindigkeitsbestimmende Schritt im Mechanismus der Transfer eines Protons vom protonierten Nitrosamid zum Reaktionsmedium sein muß.相似文献
3.
Gorkunenko O. A. Vdovichenko A. N. Chervinskii A. Yu. Kapkan L. M. Vaiman G. E. 《Theoretical and Experimental Chemistry》2004,40(1):12-16
The contributions from anisotropic magnetic screening and electronic effects to the relative chemical shifts of the NH protons in the amides and N,N-dimethylhydrazides of succinic and glutaric acids were calculated. It was shown that the splitting of the signals of the NH protons is largely determined by the redistribution of electron density in the molecule during the conformational transition. 相似文献
4.
Wataru Sakai Koki Chiga Naoto Tsutsumi 《Journal of Polymer Science.Polymer Physics》2001,39(2):247-255
This article presents the molecular orientation and second‐order optical nonlinearity of newly prepared polyureas and copolyurea with dipole moments aligned transverse to the main backbone. Nonlinear optical (NLO) polyureas, TPU and TPU2, were prepared from 2,4‐diamino‐4′‐nitroazobenzene (2R‐DIAMINE) with 4,4′‐diphenylmethane diisocyanate (DMDI) and tolylene 2,4‐diisocyanate, respectively. NLO copolyurea was prepared from DMDI with 2R‐DIAMINE and m‐phenylene diamine. TPU and TPU2 gave d33 values of 12.5 and 9.8 pm/V, respectively, under optimum poling conditions. A time‐dependent decay curve of second‐order nonlinear susceptibility was fitted well with a Kohlrausch–Williams–Watts stretched exponential function. The relaxation time of TPU2 was 4.2 × 108 s at 100 °C. Copolyurea was uniaxially drawn in ratios of 1.5 and 2.0. The average molecular angles ΦX , ΦY , and ΦZ in three laboratory frames were evaluated from the refractive indices. ΦY decreased and ΦX and ΦZ increased with an increasing draw ratio. The dependence of the second‐order harmonic intensity on the incidence angle, that is, the Maker fringe pattern, was fitted with two independent tensor components, d33 and d31, for undrawn film and five independent tensor components, d33, d32, d31, d15, and d24, for drawn films. For drawn films, Kleinman symmetry was not satisfied: d31 ≠ d15 and d32 ≠ d24. An increase in the draw ratio gave rise to a large increase in the tensor component d33. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 247–255, 2001 相似文献
5.
Mironov V. F. Petrov R. R. Shtyrlina A. A. Litvinov I. A. Gubaidullin A. T. Varaksina E. N. Konovalov A. I. 《Russian Chemical Bulletin》2001,50(4):693-696
The reaction of 4,6-bis(tert-butyl)-2,2,2-trichlorobenzo[d]-1,3,2-dioxaphosphole with phenylacetylene follows the mechanism of ipso-substitution of the tert-butyl group that is in para-position relative to the endocyclic O atom of the heterocycle, predominantly yielding 8-(tert-butyl)-2,6-dichloro-2-oxo-4-phenylbenzo[e]-1,2-oxaphosphorinine (NMR data). The structure of its hydrolysis product, 8-(tert-butyl)-6-chloro-2-hydroxy-2-oxo-4-phenylbenzo[e]-1,2-oxaphosphorinine, was proved by X-ray diffraction analysis. 相似文献