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71.
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73.
烷基极化效应与X=O键伸缩振动频率 总被引:2,自引:0,他引:2
烷基取代物R’X=0的X=0键伸缩振动频率ν与烷基R的极化效应指数PEI(R)的关系可表示为:ν=a bPEI(R)。研究结果表明,烷基的极化效应使X=0键的伸缩振动频率降低。 相似文献
74.
Crystalline title compound (1) prepared from aqueous solution of theophylline and 1,4-diaminobutane has been structurally and thermally characterized. Both the two-step TG decomposition curve and elemental analysis of the hexagonal crystals show that it consists of theophylline and 1,4-diaminobutane in 2:1 molar ratio. Actually, presence of one type of both theophyllinate anions and 1,4-diammoniumbutane dication have been indicated by FTIR spectroscopy. The molecular structure of lattice compound (1) has been determined by single crystal X-ray diffraction, where the hydrogen positions have been obtained from differential Fourier maps. It has confirmed that the crystal is really built up from these ionic constituents bound together with an extensive net of hydrogen bonds. The coupled TG-FTIR analysis of the evolved gases has revealed that the diamine is released as a whole molecule in the first decomposition step. Clathrate 1 and the proton migration in it might serve as a structural model of solid aminophylline whose crystal structure is still unknown. 相似文献
75.
The use of a low-temperature (0 degrees C) bath-assisted coupled capillary for the separation of naphthalene-2,3-dicarboxaldehyde (NDA)-derivatized dopamine and norepinephrine using the sweeping-micellar electrokinetic capillary chromatography (MEKC) mode is described. In this technique, a capillary consisting of two portions with different inside diameters is used. Therefore, the field strength inside the capillary is different. Hence, the electrophoretic migration velocities of the analytes and the electro-osmotic flow (EOF) also are different. Furthermore, when a portion of the capillary (wide portion, used for sweeping) is immersed in a low-temperature bath, the viscosity of the buffer and the retention factor of the analytes inside are increased. Thus, not only are the interactions between the SDS micelles and the analytes increased, but the SDS-analytes also move more slowly. As a result, a more complete separation can be achieved, even when the sample injection volume is large, up to approximately 2 microL. In general, when the volume of an injected sample is larger, the effects of sweeping and separation would become insufficient, especially when the retention values (k) of the analytes are quite different. However, this limitation can be improved when the low-temperature bath/coupled capillary/sweeping-MEKC mode is used. 相似文献
76.
[60]Fullerene-fused pyrazolines 1 were prepared by the reaction of C60 with alky diazoacetates under the solid-state high-speed vibration milling conditions as well as in toluene solution. Pyrazolines 1 were stable in refluxing toluene and its thermolysis process in 1,2-dichlorobenzene was investigated, the decomposition rates and activation energies of pyrazolines 1 were obtained. The current work demonstrated that the liquid-phase reaction of C60 with alkyl diazoacetates undergoes via 1,3-dipolar cycloaddition pathway at room temperature, or proceeds via carbene mechanism at a temperature of refluxing toluene, thus clarifies the previous ambiguity of its reaction mechanism. 相似文献
77.
Automatic computer programs are developed to calculate one- two-, and three-dimensional Debye functions. Prior tables of these functions are critically reviewed. Also, strategies are derived to calculate Debye temperatures from heat capacities. Both, simple three-dimensional Debye analyses and Tarasov analyses were carried out on 35 linear macromolecules. The experimental heat capacities for these analyses were collected in the ATHAS data bank. It is shown that the skeletal heat capacity of linear macromolecules is often best represented by only two vibrations per chain atom. For most of the all-carbon chain macromolecules the intramolecular skeletal heat capacity can be given by Cvs=D1[520 (28/MW)1/2] whereMW is the molecular mass andD
1 represents the one-dimensional Debye function. Polyoxides show a higher intramolecular theta temperature, but a lower intermolecular theta temperature. Double bonds and phenylene groups in the chain increase the intramolecular theta temperature.Dedicated to Prof. Dr. F. H. Müller.On leave from the Lumumba Peoples' Friendship University, Moscow, USSR. 相似文献
78.
Guan-Wu Wang Ting-Hu ZhangEr-Hong Hao Li-Juan JiaoYasujiro Murata Koichi Komatsu 《Tetrahedron》2003,59(1):55-60
The solvent-free reactions of fullerenes and N-alkylglycines with and without aldehydes (RCHO) 2a-e under high-speed vibration milling (HSVM) conditions have been investigated. Fulleropyrrolidines 4a-e (C60(CH2N(CH3)CHR), R=H (4a), C6H5 (4b), p-NO2-C6H4 (4c), p-CH3O-C6H4 (4d), p-(CH3)2N-C6H4 (4e)) were obtained in moderate yields from reactions of C60 with aldehydes 2a-e and N-methylglycine (Prato reaction). In all these solvent-free reactions, 4a was found to be formed besides 4b-e, indicating that fullerenes can react with N-substituted glycines in the absence of aldehyde to give fulleropyrrolidines. For this novel reaction, a possible reaction mechanism involving an electron transfer process has been proposed. Intrigued by this observation, the dependence of the yield on the reagent ratio for the reaction of C60 with paraformaldehyde and/or N-methylglycine was examined to search the optimal conditions. The reaction of C70 with paraformaldehyde and/or N-methylglycine under HSVM conditions was also studied and was found to give the positional isomers of [70]fulleropyrrolidines. 相似文献
79.
Summary An on-line combination of liquid chromatography, gas chromatography and mass spectrometry has been realized by coupling a quadrupole mass spectrometer to an LC-GC apparatus. Liquid chromatography was used for sample pretreatment of oil samples of different origin. The appropriate LC fraction, containing polycyclic aromatic hydrocarbons, was transferred to the gas chromatograph using a loop-type interface. After solvent evaporation through the solvent vapour exit and subsequent GC separation, the compounds were introduced into the mass spectrometer for detection and identification. The GC column was connected to a short piece of deactivated fused silica that protruded into the ion source. The total analytical set-up allowed the direct analysis of oil samples after dilution in n-pentane without any sample clean-up. Detection limits are about 40 pg in the full scan mode and about 1 pg with selective ion monitoring, i.e. 20 ppb and 0.5 ppb respectively. 相似文献
80.
D. K. Mansfield L. C. Johnson A. Mendelsohn 《International Journal of Infrared and Millimeter Waves》1980,1(4):631-640
A modulated far-infrared laser interferometer which is presently operating on the PDX experiment at Princeton is described. The interferometer geometry permits the characterization of inside D, outside D as well as circular discharges. To achieve this versatility, a titanium corner cube reflector, mounted inside the PDX vacuum vessel is used in conjunction with a second visible wavelength interferometer for vibration corrections. In addition, the use of room temperature quasi-optical Schottky diodes in the far-infrared interferometer is reported. The minimum detectable line average density of the system is 5×1011 cm–3. 相似文献