Solvent influence on the carbonyl stretching band shape of ethyl trifluoroacetate

The solvent influence on the shape of the carbonyl stretching band of ethyl trifluoroacetate has been studied, Nine infrared solvents were used:cyclohexane, n-hexane, di-n-butylether, 1,2-dichloroethane, carbon tetrachloride, tetrachloroehtylene, carbon disulfide, acetonitrile and chloroform, Moment analysis and time correlation function calculation have been performed. The frequency of the band maximum is more sensible to the solvent than the half band width, the band shape and the absolute intensity. The correlation functions show non-exponential decays in a short time region (0-0,4 ps) for any solutions, and this indicate that the molecular motions do not obey a simple rotational diffusion model. Exponential decays are shown at times longer than 0,4 ps,. Relaxation time and solvent viscosity have a quite linear relationships, but 1,2-dichloroethane and chloroform solutions follow a different behaviour.     

Raman anisotropic bandwidth study of C=O stretching vibration of methyl isobutyl ketone: role of van der Waals' volume of the interacting systems

The bandwidth (FWHM) of the anisotropic component (Gamma(aniso)) of methyl isobutyl ketone (MIBK) for different concentrations of solvents varying from 10 to 90% was measured and was plotted as a function of solvent concentrations. In lower solvent concentration, the graph shows a curvature with a discontinuity which occurs between 40 and 60% and in higher solvent concentration, the graph shows a straight line for most of the solvents. In order to interpret the complicated behaviour we have taken into accounts the van der Waals' volume (V(w)) of the sphere of influence in solute dissolved in all solvents. Considering the role of van der Waals' volume in these systems the parameter Gamma(omega)=ln(Gamma(aniso)/V(w)) was plotted at different solvent concentrations. The graph shows a straight line for the entire region. In order to study the influence of screening effect on the bandwidth, the capacitances of the liquid mixture at different solvent concentrations varying from 10 to 90% were measured for all the solvents. The plot of capacitance at different solvent concentrations for each solvent shows a discontinuity around 50% of solvent concentration.     

烷基极化效应与X=O键伸缩振动频率

烷基取代物R'X=O的X=O键伸缩振动频率ν与烷基R的极化效应指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=O键的伸缩振动频率降低。     

Microviscosity dependence of the Raman band shape of methyl-isobutyl ketone

The Raman band shape analysis of the CO stretching mode of vibration of methyl-isobutyl ketone in solution phase reveals that macroscopic consideration of hydrodynamic force is not sufficient to correlate the vibrational relaxation rate (τ_v⁻¹) with parameter ƒ(ϱ, η, n), involving dynamic viscosity (η). The band shape analysis was therefore attempted taking the microscopic parameter, microviscosity (η_m) into account through a modified parameter ƒ_m. The correlation of τ_v⁻¹ with ƒ_m is reported.     

The temperature effect on the OH stretching vibration band of hydrogen bonded complexes

The temperature effect on the infrared spectra of hydrogen bonded systems has been analysed in terms of a stochastic model. Two different sources of this effect on protonic vibration bands have been shown. For weaker hydrogen bonds with an asymmetric potential energy curve the main factor seems to be a lowering of the average bridge length with decreasing temperature. Numerical results regarding the coefficient dν_OH/dT are in good agreement with experiment. In the case of moderately strong symmetric hydrogen bonds the main factor seems to be a population change of split tunnelling levels.     

Profile analysis of PO3-symmetric stretching infrared band

Studies by vibrational spectroscopy of biological systems usually deal with band frequencies and frequency shifts. Band shape analysis can give interesting information about the dynamic behaviour of biological molecules. The main object of this work is the FTIR band shape analysis of the PO₃-symmetric stretching mode of 5′-GMP in H₂O and μ solutions. The study of the concentration effects in both solvents reveals that while the frequency remains constant the FWHH increases in a critical concentration range (0.32 mol dm⁻³ – 0.44 mol dm⁻³). A qualitatively similar change has been previously observed in the ν_max of some bands (ref. 1). Moments analysis and time correlation functions calculations have been performed. The results obtained for M₂ and M₃ in H₂O and ²H₂O solutions indicate that the observed band shape follows neither a Cauchy nor Gauss function. Apparently as the 5′-GMP concentration increases, the relaxation time, τ, decreases. Solvent change from H₂O to ²H₂O produces a slight decrease in band symmetry and a increase in τ. FWHH and τ values are interpreted according to relaxation processes.     

Integral intensities of the IR bands of the stretching vibrations of the NH,C=O,and C=C groups in theVinca alkaloids

Summary 1. The frequencies and integral intensities of the bands of the stretching vibrations of the NH, C=O, and C=C groups in some indoline, indole, and hydroxyindole alkaloids and certain other compounds have been investigated.2. From the changes in the intensities of the NH bands in vincanine, akuammicine, vinervine O-methyl ether, and their dihydro derivatives, it has been concluded that the first-mentioned compounds contain chelate bonds.3. On the basis of the results of the measurements of the intensities for vincanine and dihydrovincanine, the bands in the 1500–1700 cm^–1 region have been identified.4. The bands in the 1600–1700 cm^–1 region of a number of natural alkaloids are due to the complex vibrations of the whole grouping.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 3, pp. 185–192, 1966     

Ion association dynamics in aqueous solutions of sulfate salts as studied by Raman band shape analysis

A new perspective is shown on the interaction between the sulfate ion and its counter cation in aqueous solutions. We propose the dynamic exchange model of ion association instead of the conventional static equilibrium model. The concentration dependence of the Raman band shape of the totally symmetric (a(1)) SO stretch mode of the sulfate ion is investigated systematically for four sulfate ions, MgSO(4), (NH(4))(2)SO(4), K(2)SO(4), and Li(2)SO(4). The concentration dependence of the a(1) Raman band shape in the MgSO(4) system is successfully reproduced by the analysis based on the dynamic exchange model. As a result, quantitative information about the extremely dynamic nature of the ion association has been obtained: the mean time between associations is a few picoseconds and the mean lifetime of association is several hundred femtoseconds.     

Chemistry of stable iminopropadienones, RN=C=C=C=O

The synthesis, spectroscopic properties, and chemical reactions of the stable (neopentylimino)-, (mesitylimino)-, and (o-tert-butylphenylimino)propadienones (6) are reported. Nucleophilic addition of amines affords the malonic amidoamidines 7 and 8. 3,5-Dimethylpyrazole reacts analogously to form 9b. Addition of 1,2-dimethylhydrazine produces pyrazolinones 10-12. Addition of N,N'-dimethyldiaminoethane, -propane, and -butane gives diazepine, diazocine, and diazonine derivatives 13-15, respectively (X-ray structures of 13c, 14a, and 15a are available). The mesoionic pyridopyrimidinium olates 18 are obtained by addition of 2-(methylamino)pyridine (X-ray structure of 18b available). Primary 2-aminopyridines afford the pyridopyrimidininones 20-29 and 31 (X-ray structure of 21a available), and 2-aminopyrimidines and 2-aminopyrazine afford pyrimidopyrimidinones and pyrazinopyrimidinones 33-35. Pyrimidoisoquinolinone 36 results from 1-aminoisoquinoline and pyridoquinolinone 40 from 8-aminoquinoline. 2-Aminothiazoline and 2-aminothiazole afford thiazolopyrimidinone derivatives 41-43 (X-ray structure of 43a available).     

醇溶剂对羰基(C=O)紫外吸收的定量影响

以各种醇为溶剂测定了丙酮和环己酮的羰基紫外吸收能量△E,讨论了△E与醇分子结构的关系。结果表明△E与醇分子中烷基的极化效应指数PEI有良好的线性关系:△E=a bPEI     

Solvent effects on the oxidation of RuIV=O to O=RuVI=O by MnO4-. hydrogen-atom versus oxygen-atom transfer

The kinetics of the oxidation of trans-[RuIV(tmc)(O)(solv)]2+ to trans-[RuVI(tmc)(O)2]2+ (tmc is 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, a tetradentate macrocyclic tertiary amine ligand; solv = H2O or CH3CN) by MnO4- have been studied in aqueous solutions and in acetonitrile. In aqueous solutions the rate law is -d[MnO4]/dt = kH2O[RuIV][MnO4-] = (kx + (ky)/(Ka)[H+])[RuIV][MnO4-], kx = (1.49 +/- 0.09) x 101 M-1 s-1 and ky = (5.72 +/- 0.29) x 104 M-1 s-1 at 298.0 K and I = 0.1 M. The terms kx and ky are proposed to be the rate constants for the oxidation of RuIV by MnO4- and HMnO4, respectively, and Ka is the acid dissociation constant of HMnO4. At [H+] = I = 0.1 M, DeltaH and DeltaS are (9.6 +/- 0.6) kcal mol-1 and -(18 +/- 2) cal mol-1 K-1, respectively. The reaction is much slower in D2O, and the deuterium isotope effects are kx/kxD = 3.5 +/- 0.1 and ky/kyD = 5.0 +/- 0.3. The reaction is also noticeably slower in H218O, and the oxygen isotope effect is kH216O/kH218O = 1.30 +/- 0.07. 18O-labeled studies indicate that the oxygen atom gained by RuIV comes from water and not from KMnO4. These results are consistent with a mechanism that involves initial rate-limiting hydrogen-atom abstraction by MnO4- from coordinated water on RuIV. In acetonitrile the rate law is -d[MnO4-]/dt = kCH3CN[RuIV][MnO4-], kCH3CN = 1.95 +/- 0.08 M-1 s-1 at 298.0 K and I = 0.1 M. DeltaH and DeltaS are (12.0 +/- 0.3) kcal mol-1 and -(17 +/- 1) cal mol-1 K-1, respectively. 18O-labeled studies show that in this case the oxygen atom gained by RuIV comes from MnO4-, consistent with an oxygen-atom transfer mechanism.     

高分辨偏正拉曼光谱对丙酸酐C=O振动模的拉曼光谱非一致效应研究

根据C=O振动的各向同性和各向异性拉曼光谱和红外光谱特点讨论研究了丙酸酐分子的局部有序排列以及振动耦合机理. 利用三级联共聚焦拉曼光谱仪测定了不同浓度丙酸酐的各向同性与各向异性拉曼光谱图, 分别采集了丙酸酐在四氯化碳和甲醇中的光谱以及不同极性溶剂中的光谱, 具体分析了丙酸酐C=O振动模的浓度效应、 溶剂效应以及拉曼光谱非一致效应(NCE). 结果表明, 丙酸酐C=O振动模的NCE效应随着浓度的降低而减小; 随着溶剂极性的减小而增加. 利用密度泛函理论的B3LYP-D3/31-311G(d,p)基组计算了丙酸酐单体和二聚体的几何稳定构型, 用聚集态理论模型解释了丙酸酐分子的NCE效应、 浓度效应与溶剂效应. 理论计算结果与实验结果相吻合.     

The intensity of the C=O band in the infrared spectra of some carbonyl-containing heterocyclic compounds

Summary The high values for the intensity of infrared bands of the C=O group in a number of carbonyl-containing heterocyclic compounds (pyridones, quinolones, pyrones, etc.) shows the increased polarity of the exocyclic C=O bond in these compounds. This permits us to consider them to a definite degree as aromatic compounds in the same way as is done for tropones, sydnones, and diphenylcyclopropenone.We take this opportunity to thank N. P. Posherina for kindly supplying the-pyrones.