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1.
Meyers CY Chan-Yu-King R Hua DH Kolb VM Matthews WS Parady TE Horii T Sandrock PB Hou Y Xie S 《The Journal of organic chemistry》2003,68(2):500-511
Most alkyl phenyl sulfones are readily alpha-chlorinated with CCl(4) and alpha-brominated with CBrCl3 in KOH-t-BuOH via radical-anion radical pair (RARP) reactions. While isopropyl mesityl sulfone (4) is easily alpha-chlorinated with CCl(4), it was completely recovered when treated with the more reactive CBrCl3. Subsequent investigations showed the latter result to be due to the poor acidity of 4 together with the rapid depletion of CBrCl3 and KOH by their reaction with each other, and led to a variety of other important results. 4-Hydroxyphenyl isopropyl sulfone (6) is unreactive with either CCl4 or CBrCl3 in KOH-t-BuOH, its phenoxide anion strongly reducing the electronegativity of the sulfonyl group, thereby inhibiting alpha-anion formation. This effect is reversed by the electron-withdrawing influence of two alpha-phenyls, so that benzhydryl 4-hydroxyphenyl sulfone (8) is readily alpha-halogenated in KOH-t-BuOH with CCl4 or CBrCl3. On further contact with KOH-t-BuOH the alpha-halogenated sulfones from 8 are decomposed into benzophenone and phenol. While the alpha-halogenated derivatives of 4-methoxyphenyl benzhydryl sulfone (9) are stable to base, they are decomposed even under mildly acidic conditions into 4-methoxyphenyl 4-methoxybenzenethiolsulfonate (9c), phenol, and benzophenone. Mono-alpha-halogenation of benzyl phenyl sulfone (10) enhances the rate of the subsequent halogenation, so that alpha,alpha-dihalogenation is attained while much substrate is still present and the mono-alpha-halogenated product is not detected. The ease of reductive debromination of alpha-bromo sulfones with Cl3C- was correlated with the stability of the formed alpha-anions, explaining the success with alpha-bromobenzylic sulfones but failure with alpha-bromoalkyl sulfones. In the presence of air and the absence of competing halogenation, formation of the alpha-anions of alkyl aryl sulfones is quickly accompanied by oxidative cleavage by atmospheric O2, leading to the formation of arenesulfonyl alcohols, arenesulfonyl halides, and haloarenes. 相似文献
2.
T. Sandrock T. Danger E. Heumann G. Huber B. H. T. Chai 《Applied physics. B, Lasers and optics》1994,58(2):149-151
We report, to our knowledge for the first time, Continuous Wave (CW) laser emission at room temperature of Pr:LiYF4 (Pr.YLF) at six wavelengths: 522, 545, 607, 639.5, 720 and 907.4 nm. The pump source was an argon-ion laser tuned to a wavelength of = 457.9 nm. The maximum output powers at 522 nm (3Pi 3H5) and 639.5 nm (3P0 3F2) were 144 and 266 mW, respectively. We also observed CW laser action of Pr:GdLiF4 (Pr: GLF) at = 639 nm and of Pr:KYF4 (Pr: KYF) at = 642.5 nm. 相似文献
3.
Self-starting mode locking of a Nd:glass fiber laser by use of the third-order nonlinearity of low-temperature-grown GaAs 总被引:5,自引:0,他引:5
Leitner M Glas P Sandrock T Wrage M Apostolopoulos G Riedel A Kostial H Herfort J Friedland KJ Däweritz L 《Optics letters》1999,24(22):1567-1569
We present a diode-pumped Nd:glass fiber laser, emitting at 1060 nm, that is passively mode locked by fast nonlinear loss in low-temperature-grown GaAs (LT-GaAs). This new mode-locking mechanism is based on intensity-dependent defocusing in LT-GaAs that occurs after nonresonant generation of free carriers by two-photon absorption. Mode locking is self-starting and produces pulses as short as 4.1 ps. 相似文献
4.
A series of comprehensive hydride databases have been constructed and made freely available on the Internet (URL http://hydpark.ca.sandia.gov).
They include extensive listings of alloys reported to hydride, detailed engineering properties on selected hydrogen-storage
elements and alloys and a hydride-applications database. These databases and an associated reference database are described,
along with other hydride information available on the web site. The databases were created under the auspices of the International
Energy Agency (IEA) with financial support from the U.S. Department of Energy (DOE) and Internet service support from the
Sandia National Laboratories (SNL).
Received: 21 August 2000 / Accepted: 6 November 2000 / Published online: 9 February 2001 相似文献
5.
Keith Sandrock 《The Journal of the Operational Research Society》1988,39(5):467-475
The solution of the classical transportation problem (as generally presented) can be mastered very quickly. The fixed-charge problem is another matter. The reason is that the introduction of fixed costs in addition to variable costs results in the objective function being a step function. Fixed-charge problems are usually solved, therefore, by using sophisticated computer software. This paper deviates from that approach. It presents a low-tech. algorithm for the solution of small, fixed-charge problems. 相似文献
6.
A method was developed for the hydroboration of alkenyl-containing organotrifluoroborates to generate dibora intermediates. The reactivity differences between organotrifluoroborates and trialkylboranes facilitated the cross-coupling of the borane moiety of these intermediates in a highly chemoselective fashion with aryl halides, leaving the trifluoroborate intact for subsequent transformation. A one-pot hydroboration/two-directional cross-coupling sequence was also demonstrated, providing the fully elaborated products in good yields. These conditions were also amenable in the cross-coupling of trialkylboranes to halo-containing organotrifluoroborates. The stability of the trifluoroborate moiety to these conditions allows simple and efficient strategies for complex molecule construction. 相似文献
7.
Ternary Chlorides in the Systems NaCl/HoCl3 and NaCl/ErCl3 Phase diagrams of the systems NaCl/HoCl3 and NaCl/ErCl3 were determined by means of DTA and high-temperature XRD. There exist compounds Na3LnCl6, NaLnCl4 (Ln ? Ho, Er) and NaHo2Cl7. NaHoCl4 undergoes a phase transition at 374°C from the NaGdCl4? to the NaErCl4? type of structure. The thermodynamic functions for the formation of the compounds from NaCl and LnCl3 were determined by solution calorimetry and e.m.f. measurements in galvanic cells for solid electrolytes. The compounds NaLnCl4 are the most stable ones. 相似文献
8.
Physics of Atomic Nuclei - Investigation of lepton propagation through matter is of importance for cosmic-ray physics and neutrino astronomy. The diffractive scattering of virtual photons is... 相似文献
9.
H. J. Seifert J. Sandrock G. Thiel 《Journal of Thermal Analysis and Calorimetry》1986,31(6):1309-1318
The pseudobinary systems ACl/CeCl3 (A=Na-Cs) were reinvestigated by means of DTA. The following compounds were found and identified through their X-ray patterns (primarily detected compounds in italics):NaCe
1.67
Cl
6; K3CeCl6, K2CeCl5,KCe
1.67
Cl
6;Rb
3
CeCl
6, Rb2CeCl5,RbCe
2
Cl
7; Cs3CeCl6, Cs2CeCl5,CsCe
2
Cl
7. The compounds A2CeCl5 crystallize with the K2PrCl5 structure. The high-temperature modifications of the compounds A3CeCl6 have the cubic elpasolite structure. The hexagonal unit cell of KCe1.67Cl6 is related to the CeCl3 structure: 0.33 Ce3+ are substituted by one Ks+. The structure of CsCe2Cl7 can be described with a hexagonal subcellZ=4,a=9.72 andc=14.94 Å; however, small superstructure reflexions reduce the symmetry.The thermodynamic functions for the reactionsnACl+CeCl3=A
n
CeCl
n+3(A=K, Rb) were determined by means of e.m.f. measurements.Measurements of the e.m.f.E vs. T yielded the Gibbs enthalpiesG
r
. The temperature-dependence was found to be linear.The most important result is the formation of the elpasolites (A3CeCl6) and ACe2Cl7.
Presented as a poster at the 8th ICTA, Bratislava, 1985.
This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. 相似文献
Zusammenfassung Die pseudobinären Systeme ACl/CeCl3 (A=Na-Cs) wurden mittels Differenzthermoanalyse (DTA) neu untersucht. Folgende Verbindungen wurden gefunden und durch ihre Röntgenbeugungsmuster charakterisiert (erstmalig nachgewiesene Verbindungen sind kursiv):NaCe 1.67 Cl 6; K3CeCl6, K2CeCl5,KCe 1.67 Cl 6;Rb 3 CeCl 6, Rb2CeCl5,RbCe 2 Cl 7; Cs3CeCl6, Cs2CeCl5,CsCe 2 Cl 7. Die Verbindungen A2CeCl5 kristallisieren im K2PrCl5-Typ. Die Hochtemperaturmodifikationen der Verbindungen A3CeCl6 liegen in der kubischen Elpasolith-Struktur vor. Die hexagonale Elementarzelle des KCe1.67Cl6 ist mit der CeCl3-Struktur verwandt: 0,33 Ce3+ sind durch ein K+ ersetzt. Die Struktur des CsCe2Cl7 kann mit einer hexagonalen Pseudozelle beschrieben werden:a=9,72;c=14,94Å;Z=4; schwache Überstrukturreflexe reduzieren jedoch die Symmetrie. Die thermodynamischen Funktionen für die Reaktionen:n ACl + CeCl3=A n CeCl n+3 (A=K, Rb) wurden durch EMK-Messungen bestimmt. Messungen der Abhängigkeit von e. m. f.E gegenT ergaben die Gibbs-EnthalpienG r . Es wurde eine lineare Temperaturabhängigkeit gefunden. Als wichtigstes Resultat ist die Bildung von Elpasoliten (A3CeCl6) und von Verbindungen (ACe2Cl7) anzusehen.
ACl/CeCl3, A . - ( ):NaCe 1.67 Cl 6; K3CeCl6, K2CeCl5,KCe 1.67 Cl 6;Rb 3 CeCl 6, Rb2CeCl5,RbCe 2 Cl 7; Cs3CeCl6, Cs2CeCl5 CsCe 2Cl7. A2CeCl5 K2PrCl5. A3CeCl6 . KCe1.67Cl6 CeCl3, 0,33 Ce3+ . CsCe2Cl7 a=9,72 Å,c=14,94 Å Z=4. , . n ACl + CeCl3=A n CeCl n+3(A=K, Rb) . . . . . .E , G r . ACe2Cl7.
Presented as a poster at the 8th ICTA, Bratislava, 1985.
This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. 相似文献
10.
We report on the laser emission of erbium-doped fluoride glasses in the spectral range from 2.7 to 2.8 mum . The pump source was a fiber-coupled InGaAs semiconductor laser emitting near lambda(p)~970 nm . The laser performance of bulk samples with various ErF(3) contents was investigated with respect to the optimum doping concentration, which is estimated to be higher than 8 mol. %. A maximum output power of P(out) > 160 mW and a slope efficiency of eta = 10% were achieved. Results are compared with previously published data on erbium-doped ZBLAN fiber and LiYF(4) crystal lasers. 相似文献