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1.
The Raman spectra of the carbon—chlorine symmetric stretching mode, ν4, of the Group IVA methylmetal trichlorides (CH3MCl3, M  C, Si, Ge, Sn) were acquired in a number of solvents of varying molecular properties. Non-linear curve fitting procedures were used to separate the four band components resulting from chlorine isotope splitting.The band maxima of the two lighter members of the series were observed to shift to lower frequency with increasing solvent polarizability, indicating the predominance of solute—solvent dispersion forces. In the germanium and tin compounds, on the other hand, the peak frequencies were correlated, instead, with solvent dipole moment. This result is in contrast to earlier studies on the ν1 (CH3 symmetric stretching) vibration, for which dispersion interactions are the dominant frequency displacement mechanism in all four compounds.The bandwidths of the ν4 vibration were found to depend on dipolar interactions in the germanium and tin compounds. However, this correlation was not observed for the two lighter series members, nor for the carbon—chlorine antisymmetric stretching vibration in CH3SnCl3.  相似文献   

2.
Infrared spectra of C2H5NHD and C2H5ND2 in the region of the amino group stretching vibrations show clearly recognizable splittings due to the presence of the rotamers. In the neat liquid and concentrated carbon tetrachloride solutions of C2H5ND2, the intensity change of two components of the symmetric ND2 stretching vibration with decrease of temperature can be explained by transition of associated molecules in the gauche to such in the trans form. In crystallized C2H5ND2 and C2H5NH2, the reduction of the gauche constituent of the symmetric stretching mode to a weak shoulder confirms the practically exclusive presence of the trans form.  相似文献   

3.
Infrared and Raman spectra of neat propylamine in the NH2 stretching and deformation vibration regions are compared. For the symmetric stretching vibration in the two spectra, opposite intensity relations are found, from which the appearance of only one i.r. but two Raman bands of the vibration is understandable. The wavenumbers for the symmetric vibration and the deformation vibration overtone are lower in the i.r. than in reported polarized Raman spectra. The influence of the reduced data on the Fermi resonance analysis of νs and 2δ is discussed.  相似文献   

4.
The NMR spectra of acetone, adamantanone and 1-adamantanecarbonitrile have been studied in the presence of Eu(fod)3 in various solvents. A substantial solvent dependence is found for the association constants between shift reagent and substrate. The magnitude of the association constants is correlated with solvent polarity, and a tenfold decrease in K1 is observed upon changing from carbon tetrachloride to the more polar dichloromethane. Only a very small solvent dependence is observed for the bound shifts. The relative bound shifts (and therefore the structures of the LS complexes) are found to be solvent independent. The small solvent dependence of the absolute magnitude of the bound shifts for the LS complexes is suggested to result from experimental errors.  相似文献   

5.
The pressure and temperature dependence of the symmetric stretching vibration band, ν1, of the the sulphate ion in ammonium sulphate (rendered weakly infrared active by the crystal field) was investigated. The sudden increase in intensity at the transition temperature has been found to be accompanied by an equally sharp shift in frequency. A pressure-temperature phase diagram for the ferroelectric phase transition of ammonium sulphate has been obtained. The contributions to the transition mechanism made by the order-disorder change for the NH+4 orientations, the strengthening of the hydrogen bond and the distortion of the SO=4 ions are discussed.  相似文献   

6.
The intramolecular structure of oligomeric polyethylene (PE) in solvent mixtures of α-chloronaphthalene and carbon tetrachloride, α-chloronaphthalene and deuterated octane, and α-chloronaphthalene and deuterated hexadecane was studied at 35°C. by a high-resolution nuclear magnetic resonance technique. It was clearly shown that the n-alkanes show no detectable selective solvent absorption in these systems. The conformational structure (Pp), which was formed in “bulky” aromatic solvents when the chain length was greater than 16, was significantly destroyed by the presence of carbon tetrachloride, octane, or hexadecane in the above-mentioned solvent mixtures. Therefore, the “bulky” aromatic solvents, such as α-chloronaphthalene and 9-chloroanthracene, can be classified as Pp-structure-promoting solvents, in which the PE remains in the Pp conformation. In contrast, carbon tetrachloride and linear alkanes are Pm-structure-promoting solvents, in which the PE does not exhibit any Pp structure but is in the disordered Pm conformation. It is speculated that the Pp structure is caused by a “chain-fold” mechanism.  相似文献   

7.
Raman spectra of p-nitroaniline in supercritical water and supercritical alcohols were measured, and the effects of solvents on the NO 2 and NH 2 stretching modes were investigated. The intensity and frequency of the NO 2 stretching mode significantly changed as a function of the solvent density and temperature. The frequency of the NO 2 stretching mode correlated with the absorption peak energy of the S 1<--S 0 transition. On the other hand, the vibrational frequency of the NH 2 stretching mode did not correlate with the absorption peak shift, although it had a large frequency shift as a function of the density. The correlation between the NO 2 frequency and absorption peak energy suggested that the solvent effects of supercritical water and supercritical alcohols were similar to those for nonpolar solvents. The density functional calculation using the polarizable continuum model and p-nitroaniline-water clusters qualitatively reproduced the density dependence of the NO 2 stretching mode as well as the solvent polarity dependence. Detailed vibrational analysis revealed that the coupling between the NO 2 and C-NH 2 vibrational motions at the harmonic level has an important effect on the intensity and frequency shift of the NO 2 stretching mode. The frequency shift of the NH 2 stretching mode correlated with the degree of hydrogen bonding between the solvent molecules estimated from NMR measurements [Hoffmann M. M.; Conradi, M. S. J. Phys. Chem. B. 1998, 102, 263]. The existence of intermolecular hydrogen bonding around the NH 2 group was demonstrated even at low-density conditions.  相似文献   

8.
A general method for the determination of 5–1000 γ of osmium involves extraction of osmium tetroxide with chloroform or carbon tetrachloride, followed by shaking the organic solvent with a sulfuric acid solution, of thiourea to form red Os(NH2CSNH2)6+3, whose color intensity is measured photometrically. A sharp separation of osmium from ruthenium can be obtained by reducing Os(VIII) and Ru(VIII) with ferrous sulfate and then oxidizing Os(IV) to Os(VIII) with nitric acid; ruthenium remains reduced and is not extracted by chloroform or carbon tetrachloride.  相似文献   

9.
A series of alkylammonium-alkylcarbamates with different chain length including transdermal permeation enhancer Transkarbam 12 have been prepared and characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), temperature-dependent Fourier transform infrared spectroscopy (FTIR) and temperature-dependent X-ray powder diffraction. Four transitions have been observed including solid-solid transition (I), melting (II), decomposition of the carbamate salt (III) and boiling of the released amine (IV). The first transition was connected with rearrangement of the hydrocarbon chain packing and unusual shift of symmetric CH2 stretching vibration in the IR spectra to lower wavenumbers indicated increase of conformational order. The second transition represented melting of the molecule and the third one was attributed to the decomposition of the carbamate salt into two amine molecules and carbon dioxide as evidenced by combination of DSC and TGA curves.  相似文献   

10.
Infrared (4000-50 cm?1) and Raman spectra are reported of methylamine, methylamine-d1 and methylamine-d2 trapped in argon and nitrogen matrices at 4–20 K. An anomalous intensity variation was found for the NH2 wagging mode of methylamine isolated in nitrogen matrices, while in argon matrices the NH2 wagging absorption exhibited a complex structure due to matrix site effects. A normal coordinate analysis was carried out using a new assignment of the NHD twisting frequency. Barriers to internal rotation in argon and nitrogen matrices, calculated from the observed torsional frequencies, are compared with the gas phase value.  相似文献   

11.

Quantum-chemical calculations of the 3-(hydroxymethyl)piperidine molecule conformers were performed at the B3LYP/6-31+G** level of theory, and four most stable conformations with different relative orientation of CH2OH and N–H groups were determined. The optimized structures, vibration frequencies, and band intensities in the spectra of the conformers were obtained. The conformational equilibria of the most stable rotational isomers in solvents of different polarity was studied within the polarizable continuum model. According to the results of calculations, the conformational equilibrium in solution is substantially changed on varying the solvent polarity. This conclusion was confirmed by comparison with IR absorption spectra of 3-(hydroxymethyl)piperidine solutions in carbon tetrachloride in the region of ОН-stretchings.

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12.
The far-infrared spectra (200-20 cm−1) of hydrogen-bonded complexes involving chloroform, 3-chloropropine, phenylacetylene and a number of dihalonitromethanes with dimethylsulphoxide and N,N-dimethylformamide have been investigated in carbon tetrachloride solution. In all cases, broad, low intensity bands near 100 cm−1 have been observed and are assigned to the intermolecular stretching vibration νσ. The force constants Kσ have been calculated in diatomic approximation.  相似文献   

13.
Measurements of the spin-lattice relaxation times (T1) of solvent protons have been performed on systems containing mixed solvents with and without polymer. It has been found that the motion of solvent is selectively affected by polymers present in the system. Polyisobutylene (10%) in mixed solvents of carbon tetrachloride (or cyclohexane) and dichloromethane at various proportions produces little effect on T1 values of dichloromethane, but it affects significantly the T1 values of cyclohexane; whereas poly(methyl methacrylate) (10%) in carbon tetrachloride and dichloromethane (or acetone) selectively associates with dichloromethane (or acetone), resulting in an approximate 50% reduction of the T1 values for dichloromethane (or acetone). In systems of poly(methyl methacrylate) and three mixed solvents of carbon tetrachloride, dichloromethane, and cyclohexane, the polymer (10%) has a negligible effect on the T1 values of cyclohexane, but brings about a 50% reduction of the T1 values of dichloromethane. These phenomena are discussed in terms of local selective interactions between the solvent molecules and the polymeric chain segments.  相似文献   

14.
The chemical shift of elemental xenon is extremely sensitive to the environment. In aprotic solvents, the presence of xenon has little effect on the solvent structure, and preferential solvation is not observed in any mixed solvent system. Consequently, xenon shifts can reveal the presence of short range order in certain liquids. Chemical shift data are presented for several model systems, including mixtures of different alkanes, alkanes with benzene, alkanes with acetone, and carbon tetrachloride with dimethylformamide (DMF). In certain cases, the xenon shift is strongly non-linear with composition. This effect arises from a specific interaction between the two solvents in the CCl4-DMF system, while it reflects short range liquid order in the acetone-alkane systems. This effect is also apparent in the deviation of the densities of the acetone-alkane mixtures from ideality.  相似文献   

15.
Isotherms of adsorption of oleic, linoleic, and linolenic acids on magnetite from solutions in carbon tetrachloride and hexane are measured. When CCl4 is used as a solvent, the adsorption values increase in the following order: oleic, linoleic, and linolenic acid. In the case of hexane, the order is opposite. Adsorption isotherms of the fatty acids on aggregated magnetite are described in terms of the theory of volume filling of micropores. It is disclosed that, in the case of CCl4 , the limiting adsorption values and characteristic energies of the process increase in a series: oleic, linoleic, and linolenic acid, but in the case of hexane, they decrease in the same sequence. Upon the adsorption of fatty acids from solutions in CCl4 and hexane on finely dispersed magnetite, molecules of the acids and solvents compete for the active sites on the adsorbent surface. The number of double bonds in the molecules of unsaturated fatty acids and the desolvation of both the adsorbent surface and adsorbate molecules substantially affect the adsorption of these acids. The effect of the solvents is most pronounced for the adsorption of oleic acid, decreasing with a rise in the number of double bonds in a fatty acid molecule.Translated from Kolloidnyi Zhurnal, Vol. 66, No. 6, 2004, pp. 779–783.Original Russian Text Copyright © 2004 by Korolev, Ramazanova, Yashkova, Balmasova, Blinov.  相似文献   

16.
Isotropie Raman linewidths or several CH3 symmetric stretching bands aie measured in the neat liquid and in carbon tetrachloride solution. Homogeneous and inhomogeneous linewidths are separated by applying the binary collision model and the local number density distribution model. Results agree fairly well with those obtained from the picosecond techniques.  相似文献   

17.
The association of bis (p-chlorophenyl) phosphoric acid with various organic solvents as well as its dimerization in these solvents was investigated. In inert solvents like kerosene, carbon tetrachloride and benzene, dimerization is very high and decreases with increasing polarity of the solvent. In polar solvents like alcohols and ketones, a strong association between HA and solvent molecules exists. The association constants were determined; the values may be regarded as a measure for the basicity of the solvents in question. The following order of the increasing basicity of the solvents was established: hydrocarbons and chlorinated hydrocarbons < ethers < ketones < alcohols.  相似文献   

18.

This study aimed to investigate CO2 absorption using chemical solvent of amine H2O-TEA-CO2 in presence of activated carbon (AC) particles. The studied experimental range includes the temperature in range of 293–333 K, pressure in range of 3.5–9.5 bar, the concentration of solvents in range of 2.5–8.5 wt%, and amount of activated carbon in range of 0.3–0.9 kg/m3. The central composite design (CCD) with four parameters of temperature, pressure, amine concentration, and active carbon was applied in 5 levels. The physical solubility CO2 in amine solutions decreases with the increasing temperature that indicates the process is exothermic. The optimal values of temperature, pressure, concentration, and active carbon are 303.0 K, 8.00 bar, 7.00 M, 0.75 g, respectively, and 25.99% for the input variables and desirability index of 0.732. The CO2 loading, absorption capacity, and absorption percentage are obtained in the range of 0.572–1.180 molCO2/molTEA, 0.208–0.506 wt%, and 12.73–32.61% in Triethanolamine (TEA) solutions in activated carbon, respectively. All dependent variables had a p value of less than 0.05, indicating that models were significant and substantial. The result showed that the addition of solid particles to chemical solvents effectively enhances CO2 absorption.

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19.
《Chemical physics letters》1987,142(5):341-344
A Raman spectroscopic study of (CH3NH3)2HgCl4 is reported in the temperature range 299–373 K. Discontinuities in the HgCl symmetric stretching mode and in the frequency shift of the CN stretching mode indicate a new phase above 330 K. A non-linear increment of the widths of these bands confirms the transition. Arrhenius behaviour of the CN stretching mode indicates a barrier of 1234 cm−1.  相似文献   

20.
Bis[2,4‐di(trifluoromethyl)quinoline‐7‐yl]amine ( 1 ), bis[2,4‐di(trifluoromethyl)quinoline‐7‐yl]methylamine ( 2 ), bis[2,4‐di(trifluoromethyl)quinoline‐7‐yl]phenylamine derivatives, Q2NPhX; X=NO2 ( 3 a ), I ( 3 b ), H ( 3 c ), OMe ( 3 d ), and NH2 ( 3 e ), tris[2,4‐di(trifluoromethyl)quinoline‐7‐yl]amine ( 4 ), and bis[2,4‐di(pentafluoroethyl)quinoline‐7‐yl]‐4‐nitrophenylamine ( 5 ) were prepared as functional fluorophores. On irradiating the solution samples, 1 showed no noticeable alteration, whereas 2 , 3 a – d , and 4 showed emission color changes from yellowish green to blue, indicating that a photoreaction took place. Analyses of the photoproduct based on absorption and emission spectra, 1H NMR spectra, and X‐ray crystallography indicated that photocyclization reactions occurred regioselectively and quantitatively to form bent–bent dipyridocarbazoles. In 3 a – d , the reaction rates depended on the solvent polarity and the substituent on the benzene ring. The photoreactions were accelerated with decreasing solvent polarity and with increasing electron‐withdrawing character of the substituents. The photocyclization of triquinolineamine 4 was faster than that of 3 a in all solvents. The results of semiempirical quantum‐chemical PM6 calculations suggested that the observed regioselective photocyclization could be explained by stabilization of the excited triplet transition state for the bent–bent form because of the molecular geometry with the CH?NQ hydrogen bonds. The solution of 5 in MeOH displayed photoreaction‐induced self‐assembly behavior to form twisted tape‐like fibers of width 200 nm, as determined by TEM imaging.  相似文献   

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