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21.
William E. Hunter Jerry L. Atwood G. Fachinetti C. Floriani 《Journal of organometallic chemistry》1981,204(1):67-74
The crystal and molecular structure of (η5-C5H5)2Zr[C4(C6H5)4] has been determined by single crystal X-ray diffraction methods. The compound is isostructural with its titanium and hafnium analogues, and crystallizes in the monoclinic space group P21/n with unit cell parameters a = 13.790(5), b = 11.136(5), c = 18.692(7) », β = 92.82(4)°, and ?calc = 1.34 g cm?3 for Z = 4. Full-matrix least-squares refinement converged with a conventional R value of 0.049 for 2986 observed reflections. The metallocyclic ring is planar to within 0.05 », and the π-electron density is largely localized. The two independent ZrC(σ) bond lengths are 2.250(5) and 2.265(6) ». The ZrC(η5) distances range from 2.482(6) to 2.546(7) », and average 2.521(20) ». A comparison of zirconium- and hafnium-carbon bonds based on the data available shows that for M = Hf the MC bonds are shorter for all cases: C(sp), C(sp2), C(sp3), C(η5). 相似文献
22.
A one-pot synthesis of substituted imidazoles is described. The cornerstone of this methodology involves the thiazolium-catalyzed addition of an aldehyde to an acyl imine to generate the corresponding alpha-ketoamide in situ followed by ring closure to the imidazole in a one-pot sequence. The extension of this methodology to the one-pot synthesis of substituted oxazoles and thiazoles is also described. [reaction: see text] 相似文献
23.
D. A. McCombs C. S. Menon Jerry Higgins 《Journal of polymer science. Part A, Polymer chemistry》1971,9(5):1261-1270
Photolytic condensations of p,p′-dibenzoyldiphenyl sulfide, p,p′-dibenzoyldiphenyl ether, p,p′-dibenzoyldiphenylmethane, and p,p′-dibenzoyldiphenylethane with a 100-W long-wavelength ultraviolet lamp gave polypinacols having inherent viscosities ranging from 0.12 to 0.45. Treatment of the same monomers under similar conditions with a 450-W ultraviolet lamp produced polypinacols having inherent viscosities ranging from 0.04 to 0.37. 相似文献
24.
Jerry W. Slootstra Wouter C. Puijk Gerard J. Ligtvoet Jan P. M. Langeveld Rob H. Meloen 《Molecular diversity》1996,1(2):87-96
Summary Two small random peptide libraries, one composed of 4550 dodecapeptides and one of 8000 tripeptides, were synthesized in newly developed credit-card format miniPEPSCAN cards (miniPEPSCAN libraries). Each peptide was synthesized in a discrete well (455 peptides/card). The two miniPEPSCAN libraries were screened with three different monoclonal antibodies (Mabs). Two other random peptide libraries, expressed on the wall of bacteria (recombinant libraries) and composed of 107 hexa- and octapeptides, were screened with the same three Mabs. The aim of this study was to compare the amino acid sequence of peptides selected from small and large pools of random peptides and, in this way, investigate the potential of small random peptide libraries. The screening of the two miniPEPSCAN libraries resulted in the identification of a surprisingly large number of antibody-binding peptides, while the screening of the large recombinant libraries, using the same Mabs, resulted in the identification of only a small number of peptides. The large number of peptides derived from the small random peptide libraries allowed the determination of consensus sequences. These consensus sequences could be related to small linear and nonlinear parts of the respective epitopes. The small number of peptides derived from the large random peptide libraries could only be related to linear epitopes that were previously mapped using small libraries of overlapping peptides covering the antigenic protein. Thus, with respect to the cost and speed of identifying peptides that resemble linear and nonlinear parts of epitopes, small diversity libraries based on synthetic peptides appear to be superior to large diversity libraries based on expression systems.Abbreviations ABTS
2,2-azino-di-3-ethylbenzthiazoline sulfonate
- EGF
epidermal growth factor
- Mab
monoclonal antibody
- ODccd
optical density obtained using CCD camera
- RAMPO
rabbit-antimouse peroxidase
- SDS
sodium dodecylsulfate
- TGEV
transmissible gastroenteritis virus 相似文献
25.
The variation in the lifetime of flash-excited gaseous benzophenone with pressure and temperature indicates that (1) self-quenching is a relatively inefficient process for the long-lived emission, ksq = 9 × 105 M?1 s?1 (estimated from solution data) at 25°C and 1.2 × 107 M?1 s?1 at 170°C and (2) the lifetime decreases with increasing temperature as a result of photochemical and photophysical decay pathways which have significant activation energies. The importance of diffusion to the walls on lifetime measurements is discussed. 相似文献
26.
Haiges R Vij A Boatz JA Schneider S Schroer T Gerken M Christe KO 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(2):508-517
The highly explosive molecules As(N(3))(3) and Sb(N(3))(3) were obtained in pure form by the reactions of the corresponding fluorides with (CH(3))(3)SiN(3) in SO(2) and purification by sublimation. The crystal structures and (14)N NMR, infrared, and Raman spectra were determined, and the results compared to ab initio second-order perturbation theory calculations. Whereas Sb(N(3))(3) possesses a propeller-shaped, pyramidal structure with perfect C(3) symmetry, the As(N(3))(3) molecule is significantly distorted from C(3) symmetry due to crystal packing effects. 相似文献
27.
Thomas F.O. Lim Jerry K. Myers Greg. T. Rogers Paul Ronald Jones 《Journal of organometallic chemistry》1977,135(2):249-259
The regioselectivity of the hydroboration of the methylchlorovinylsilanes, ClnMe3?nSiCHCH2 (n= 0 ? 3), has been investigated using BH3←THF, 9-BBN, disiamyl- and dicyclohexylborane. Methylation of the adducts with methylmagnesium bromide is complicated by formation of tetraalkylboronates. Alkaline hydrogen peroxide oxidation of the boronates gives reasonable yields of the corresponding α- and β-trimethylsilylethanols forn= 0 and 1. Forn= 2 and 3, conversion of the adducts to the corresponding α- and β- deuteroethylsilanes by treatment with excess sodium methoxide in methanol-0-d provides a more effective means of derivatization. Addition of the alkenes,n= 2 or 3, to excess BH3←THF givesca. 90% of the α-boro-organo-chlorosilanes. For all of the alkenes, the dialkylboranes giveca. 80% of the β-boron adducts. 相似文献
28.
Springfield SA Marcantonio K Ceglia S Albaneze-Walker J Dormer PG Nelson TD Murry JA 《The Journal of organic chemistry》2003,68(11):4598-4599
In this paper, we disclose an efficient one-pot procedure for the preparation of substituted 1,8-naphthyridin-4-one analogues. Previous efforts to effect this type of transformation were complicated by the formation of benzene tricarboxylate. Via the use of excess base, the impurity formation was completely inhibited. This allowed for the clean preparation of the desired intermediate and subsequent formation of naphthyridone analogues in a single flask, which could then be crystallized directly from the reaction mixture in good yield and high purity. 相似文献
29.
Highly ordered large pore SBA-15 silica functionalized with up to 16% aminopropyl groups, which gave high catalytic activity and selectivity toward flavanone synthesis through aldol condensation and subsequent intramolecular Michael addition of benzaldehyde and 2'-hydroxyacetophenone, was synthesized for the first time via co-condensation of tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (APTES) using an amphiphilic block copolymer as the structure-directing agent. 相似文献
30.