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41.
A high-temperature pulsed slit nozzle, consisting of a circular pulsed nozzle and an interface to convert a circular flow into a slit flow has been constructed. The absorption spectrum is measured by scanning the wavelength of the monochromator equipped with a xenon arc lamp and by detecting the transmitted light through a jet with a photomultiplier. A rotationally cooled spectrum is clearly observed for aniline only when a long slit nozzle is employed. The absorptivity increases proportionally to the slit length at least up to 6 cm. The time for recording a spectrum is 3.5 min, which is reduced to several seconds by transmitting a white light through a jet and by measuring the spectrum with an optical multichannel analyzer. The detection limit is estimated to a partial vapor pressure of 0.4 torr for aniline. The present system can be conveniently used in routine analysis, because of a wide spectral coverage of the lamp source. 相似文献
42.
The reaction of alpha,beta-unsaturated imines with CO and alkenes in the presence of Ru(3)(CO)(12) as a catalyst results in a three-component coupling reaction that gives alpha,alpha-disubstituted beta,gamma-unsaturated gamma-butyrolactams. The reaction proceeds via a two-step sequence involving the initial formation of ketone derivatives by catalytic carbonylation at the beta-olefinic C-H bonds of alpha,beta-unsaturated imines, followed by the (uncatalyzed) intramolecular nucleophilic attack of the imine nitrogen on the ketonic carbon to generate a tetrahedral intermediate, which then undergoes a 1,2-ethyl migration. The reaction of a cyclic unsaturated imine, derived from the reaction of (1R)-(-)-myrtenal with tert-butylamine, gives a beta-aminocyclopentene derivative, which is formed by an aldol-type condensation of the initially formed ketone, indicating the initial formation of ethyl ketone. 相似文献
43.
Takashi Tateno Shinji Doi Shunsuke Sato Luigi M. Ricciardi 《Journal of statistical physics》1995,78(3-4):917-935
Noise effects on phase lockings in a system consisting of a piecewise-linear van der Pol relaxation oscillator driven by a periodic input are studied. The problem of finding the period of the oscillator is reduced to the first-passage-time problem of the Ornstein-Uhlenbeck process with time-varying boundary. The probability density functions of the first-passage time are used to define the operator which governs a transition of an input phase density after one cycle of the oscillator. Phase lockings in a stochastic sense are investigated on the basis of the density evolution by the operator. 相似文献
44.
N. Kawamura I. Higashino Y. Kimura M. Fujioka S. Hayashibe 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(3):173-176
Nuclearg-factors of the 1229 keV 13+/2 and 2911 keV 21+/2 level and the half-life of the 1229 keV level have been measured to beg(1229)=0.058(5),g(2911)=0.69(12) andT
1/2 (1229)=6.79(2) ns. The experimental g-factors show that the 1229 keV level has a dominant configuration of (f
7/23–), and the 2911 keV level has an almost pure (f
7/27–), configuration.The authors would like to thank the crew of CYRIC for the operation of the cyclotron. 相似文献
45.
Isozaki T Fujikawa T Takezoe H Fukuda A Hagiwara T Suzuki Y Kawamura I 《Physical review. B, Condensed matter》1993,48(18):13439-13450
46.
47.
Harada S Kumagai N Kinoshita T Matsunaga S Shibasaki M 《Journal of the American Chemical Society》2003,125(9):2582-2590
Full details of our direct Michael addition of unmodified ketones using new asymmetric zinc catalysis are described. Et(2)Zn/(S,S)-linked-BINOL complexes were successfully applied to direct 1,4-addition reactions of hydroxyketones. The first generation Et(2)Zn/(S,S)-linked-BINOL 1 = 2/1 system was effective for 1,4-addition of 2-hydroxy-2'-methoxyacetophenone (3). Using 1 mol % of (S,S)-linked-BINOL 1 and 2 mol % of Et(2)Zn, we found that a 1,4-addition reaction of beta-unsubstituted enone proceeded smoothly at 4 degrees C to afford products in high yield (up to 90%) and enantiomeric excess (up to 95%). In the case of beta-substituted enones, however, the first generation Et(2)Zn/(S,S)-linked-BINOL 1 = 2/1 system was not at all effective. The second generation Et(2)Zn/(S,S)-linked-BINOL 1 = 4/1 with MS 3A system was developed and was effective for various beta-substituted enones to afford products in good dr, yield (up to 99%), and high enantiomeric excess (up to 99% ee). With the Et(2)Zn/1 = 4/1 systems, catalyst loading for beta-unsubstituted enone was reduced to as little as 0.01 mol % (substrate/chiral ligand = 10 000). The new system was also effective for 1,4-addition reactions of 2-hydroxy-2'-methoxypropiophenone (9) to afford chiral tert-alcohol in high enantiomeric excess (up to 96% ee). Mechanistic investigations as well as transformations of the Michael adducts into synthetically versatile intermediates are also described. 相似文献
48.
49.
Masahiro Manabe Toshihiro Ochi Hideo Kawamura Hajime Katsu-ura Masaki Shiomi Mandeep Singh Bakshi 《Colloid and polymer science》2005,283(7):738-746
The partial molar volumes (Va) of 1-alkanols (carbon number, m=5, 6, 7) in - and -cyclodextrin (CD) solutions at 5.00 mmol kg–1 have been determined as a function of alkanol concentration (Ca) between 293.2 and 308.2 K by using a dilatometer. It has been observed that with an increase in Ca, Va increased in -CD solution but decreased in -CD solution, asymptotically to a value of Va in CD-free water. The dependence of Va on Ca provided the binding constant (K) of 1:1 complex, the volume change in complex formation, and the partial molar volume of complex itself. The complex formation mechanism has been discussed on the basis of these values and their carbon number dependences in the respect of geometric behavior, hydrophobic interaction, and van der Waals interaction. It is concluded that the CD cavity in water is not rigid but flexible for fitting in nicely with guest molecule. 相似文献
50.
N-Lithioketimines, generated in situ from 2-substituted benzonitriles and t-BuLi, reacted with carbon monoxide to afford five-, six- or seven-membered cyclic products, involving participation by the ortho substituents. The reactions represent new selective transformations of carbonyllithium intermediate which previously were observed to lead to complicated reactions. 相似文献