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91.
Shinichi Ueji Kazumi Nakatsu Hiroshi Yoshioka Kenji Kinoshita 《Tetrahedron letters》1982,23(11):1173-1176
The crystals of the title compound contain both intra- and inter-molecular OH?π hydrogen bonds (the first example of bifurcated OH?π bonds), the stereochemistry of which has been elucidated by an X-ray structure analysis; this bifurcated bond is also supported by the observation based on the IR spectrum of the crystals. 相似文献
92.
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95.
Summary The rise process, steady-state and decay process of the birefringence of poly--benzyl-l-glutamate solutions under the action of a rectangular pulse have been studied at 25 °C over a wide range of field strength of 1.5×103 to 3×104V/cm. The solvent used was a dichloroethane-dimethylformamide mixture of the volume ratio 991. From the decay process the average relaxation time extrapolated to zero concentration and the corresponding rotational diffusion constant were determined. The apparent dipole moment and the optical anisotropy factor were obtained from the field strength dependence of steady-state birefringence. The rise process was analyzed according to our theory which holds for arbitrary high field strength in the initial stage. The n(t)/t versus t curves for various field strengths were found to be linear in the initial stage and pass through the origin. Thus, it was concluded that the electrical orientation of poly--benzyl-l-glutamate in solution is due primarily to the permanent dipole moment. Furthermore, the value of the apparent permanent dipole moment obtained from the rise process was compared with that obtained from the steadystate birefringence.
With 7 figures 相似文献
Zusammenfassung Der Einschaltvorgang, der stationäre Zustand und das Abklingen der Doppelbrechung bei Poly--benzyl-l-glutamat-Lösungen mit einem elektrischen Impuls von rechteckiger Form werden bei 25 °C über einem großen Feldstärkebereich von 1.5×103–3×104V/cm untersucht. Als Lösungsmittel wird die Dichloräthan/Dimethylformamid-Mischung im Volumenverhältnis 991 verwendet. Aus dem Abklingvorgang werden die zur Konzentration 0 extrapolierte mittlere Relaxationszeit und die entsprechende Rotationsdiffusionskonstante bestimmt. Das scheinbare permanente Dipolmoment und der optische Anisotropiefaktor werden aus der Feldstärkeabhängigkeit der stationären Doppelbrechung ermittelt. Der Einschaltvorgang wird nach unserer Theorie, die für beliebige hohe Feldstärken im Anfangsverlauf gültig ist, analysiert. Die n(t)/t gegen t-Kurven für verschiedene Feldstärken sind geradlinig im Anfangsverlauf und laufen durch den Ursprung. Hieraus zeigt sich, daß die elektrische Orientierung von Poly--benzyl-l-glutamat in Lösungen hauptsächlich durch das permanente Dipolmoment bedingt ist. Überdies wird der aus dem Einschaltvorgang gewonnene Wert des scheinbaren permanenten Dipolmomentes mit dem aus der stationären Doppelbrechung ermittelten Wert verglichen.
With 7 figures 相似文献
96.
We propose and demonstrate a limiting procedure in which, starting from the q-lifted version (or K-theoretic five-dimensional version) of the (W)AGT conjecture to be assumed in this paper, the Virasoro/W block is generated in the r-th root of unity limit in q in the 2d side, while the same limit automatically generates the projection of the five-dimensional instanton partition function onto that on the ALE space R4/Zr. This circumvents case-by-case conjectures to be made in a wealth of examples found so far. In the 2d side, we successfully generate the super-Virasoro algebra and the proper screening charge in the q→−1, t→−1 limit, from the defining relation of the q-Virasoro algebra and the q -deformed Heisenberg algebra. The central charge obtained coincides with that of the minimal series carrying odd integers of the N=1 superconformal algebra. In the r-th root of unity limit in q in the 2d side, we give some evidence of the appearance of the parafermion-like currents. Exploiting the q-analysis literatures, q -deformed su(n) block is readily generated both at generic q,t and the r -th root of unity limit. In the 4d side, we derive the proper normalization function for general (n,r) that accomplishes the automatic projection through the limit. 相似文献
97.
The Photochemistry of Open-Chained 2,6- or 2,7-Dien-Carbonyl Compounds On 1n, π*-excitation (λ > 347 nm) citral (5) and the methyl ketone 10 isomerize to compounds A (7, 19) and B (6, 20) , whereas the phenyl ketone 11 changes into the isomer 24 of type E. Evidence is given that the conversions to A and B may arise from the 3n, π*-state of the 2,6-diene-carbonyl compounds. On 1n, π*-excitation (λ = 254 nm) 5 and 10 yield the isomers A (7, 19) and D (18, 22) , but no products of type B. Furthermore, conversion of 10 to the isomer 21 of type C is observed. Selective 1n, π*-excitation (λ = 254 nm) as well as selective 1n, π*-excitation (λ > 347 nm) of the 2,7-diene-carbonyl compounds 12 and 13 give rise to isomerization to the compounds F (25, 28) , exclusively. The intramolecular [2 + 2]-photocycloadditions are shown to be triplet processes. UV.-irradiation (λ > 280 nm) of compounds F (25, 28) furnishes the isomeric products G (26, 29) which photoisomerize to oxetanes of type H (27, 30). 相似文献
98.
Boron complexes surrounded with organic cages were controlled precisely by a remote atom placed at the bottom of the cage. A replacement of the bottom tether atom (carbon or silicon) changed the characteristics (kinetic and thermodynamic factors) of boron complexes by geometric effects. A theoretical study shows that the bottom atoms also control eigenvalues of MO. This cage complex will provide a systematic template for fine-tuning of metal complexes to create various properties. 相似文献
99.
100.
Hideaki Oike Yuka Yoshioka Shinji Kobayashi Megumi Nakashima Yasuyuki Tezuka Eric J. Goethals 《Macromolecular rapid communications》2000,21(17):1185-1190
Mono‐, bis‐, and tris(trifluoromethanesulfonate ester)s ((triflate ester)s) were prepared by the reaction of benzyl alcohol ( 1 ), 1,4‐bis(hydroxymethyl)benzene ( 2 ) and 1,3,5‐tris(hydroxymethyl)benzene ( 3 ) with trifluoromethanesulfonic anhydride in the presence of 2,6‐di‐tert‐butylpyridine. These benzylic triflate esters were applied in‐situ for the living polymerization of tetrahydrofuran (THF). The subsequent end‐capping reaction with a suitable nucleophile proceeded quantitatively to produce mono, bi‐ and, in particular, novel trifunctional telechelic poly(THF)s, respectively. 相似文献