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51.
The retroaldol-aldol isomerization of the epimeric hydroxyketones and was found to yield predominantly and , respectively, under kinetic conditions in the presence of chelating lithium cations. In hydroxylic medium is the preferred kinetic product. Under equilibration conditions and predominate. 相似文献
52.
The effect of buoyancy force on laminar boundary layer in two dimensional flow and heat transfer along a semi-infinite vertical surface, when the velocity of the on-coming stream oscillates in magnitude about a steady mean, is analysed. Two separate solutions valid for low and high frequency ranges are developed. It is found that for low frequency oscillations the phase angles of oscillatory components of skin friction and the rate of heat transfer increase as the Grashof number increases. For very high frequencies, the velocity field is of shear-wave type unaffected by the mean flow; the phase lead in the skin friction is, then, /4 and the rate of heat transfer fluctuation indicates a phase lag of /2 over that of the free stream oscillations.The authors are thankful to referee for many useful suggestions. 相似文献
53.
The structure of the local anaesthetic benzocaine was solved by direct methods and refined to anR of 0·12 for 531 observed reflections. The packing of the molecule is stabilised by N−H … O hydrogen-bonds (2–97 ?). The alkyl
chain attached to the benzene ring is intrans-trans conformation. The benzoic moiety shows a quinonoid character as found in some other local anaesthetics.
DCB contribution No. 699 相似文献
54.
Ru(P)2(TaiMe)Cl2 [P = PPh3; TaiMe = 1-methyl-2-(p-tolylazo)imidazole] possesses a cis-RuCl2 configuration. Dechlorination was carried out in acetone solution by Ag+ and the solvated species reacted with N,O-[oxinate (ox), -picolinate (pic)], O,O-[salicylate (sa), 3-formylsalicylate (3-fsa), 5-formylsalicylate (5-fsa)] and S,S-[xanthate (xan), dithiocarbamate (dtc)] chelators to yield [Ru(P)2(TaiMe)(N,O/O,O/S,S)] (ClO4)
n
(n = 1 for N,O- and S,S-chelators; n = 0 for O,O-chelators). The complexes were characterised by microanalysis, molar conductance, i.r., u.v.–vis. and 1H-n.m.r. data. Isomeric structures in some complexes were identified by 1H-n.m.r. spectra. The electronic spectra show a high intensity ( 104) m.l.c.t. transition in the visible region together with a weak shoulder ( 103) at longer wavelength. Redox studies exhibit a RuIII/RuII couple and quasireversible azo reduction. 相似文献
55.
(E)-4-(2',4',5'-trimethoxyphenyl)but-1,3-diene (4) and (E)-4-(2',4',5'-trimethoxyphenyl)but-1-ene (6), bioactive phenylbutanoids of Zingiber cassumunar, were synthesized exclusively with trans geometry. Treatment of methylmagnesium iodide with (E)-2',4',5'-trimethoxycinnamaldehyde (2), an oxidized product of abundantly available toxic (Z)-phenylpropanoid (1) of Acorus calamus, gave (E)-4-(2',4',5'-trimethoxyphenyl)but-3-en-2-ol (3) which upon dehydration with copper sulphate/silica gel under microwave irradiation for 3 min afforded 4 in 58% yield. Further, catalytic hydrogenation of 4 with 10% Pd/C afforded 4-(2',4',5'-trimethoxyphenyl)butane (5) which upon dehydrogenation with DDQ/SiO2 afforded hypolipidemic 6 in 54% yield. 相似文献
56.
57.
Nascent OH fragment product state distributions arising from unimolecular dissociation of room temperature HOONO, initiated by excitation in the region of the 2nu(OH) band, are probed using laser-induced fluorescence at sub-Doppler resolution. Phase-space simulations of the measured OH rotational distributions are consistent with the dissociation dynamics being statistical and confirm that all major features in the room temperature action spectrum belong to the cis-cis conformer. The phase-space simulations also allow us to estimate the HO-ONO bond dissociation energy of cis-cis HOONO to be D(0)=19.9+/-0.5 kcal/mol, which when combined with the known heat-of-formation data for the OH and NO(2) fragments gives DeltaH(f) (0)(cis-cis HOONO)=-2.5 kcal/mol. In addition to fragment energy release, spectral features in the cis-cis HOONO action spectrum are examined with respect to their shifts upon (15)N isotope substitution and through ab initio spectral simulation using a two-dimensional dipole surface that takes into account the influence of HOON torsional motion on the OH stretching overtone. The two-dimensional spectral simulations, using CCSD(T)/cc-pVTZ dipole surface, qualitatively reproduces features appearing in the action spectrum and suggest that the strong broad feature occurring approximately 570 cm(-1) to the blue of the cis-cis HOONO 2nu(OH) peak, likely involve excitation of HOON-torsion/OH-stretch combination bands originating from thermally populated excited torsional states. A closer examination of the predictions of the two-dimensional model with experiments also reveals its limitations and suggests that a more elaborate treatment, one which includes several additional modes, will likely be required in order to fully explain the room temperature action spectrum. Ab initio calculations of the HOON torsional potential at the CCSD(T)/cc-pVTZ level of theory are also presented and confirm that cis-perp configuration does not correspond to a bound localized minimum on the HOONO potential energy surface. 相似文献
58.
Isoelectric focusing in long immobilized pH gradient gels to improve protein separation in proteomic analysis. 总被引:2,自引:0,他引:2
The number of protein spots detected on two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) gels increases as the gel size increases. The largest commercially available systems resolve a few thousand spots, being only a fraction of the total proteome. We have developed an extremely long isoelectric focusing (IEF) system aimed at more complete protein profiling. The system is especially well suited to sensitive detection methods, such as radioactive detection. The major constraint preventing progress in this area has been the inability to create an even density gradient during the immobilized pH gradient (IPG) casting process. We demonstrate for the first time that this constraint can be effectively overcome, to enable greatly increased IEF separating power with all the advantages of IPG technology, 相似文献
59.
60.