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41.
42.
Measurements of density(ρ), viscosity(η), and refractive index(n), were carried out on α-amino acids, DL-solution at 298.15, 303.15, 308.15, and 313.15 K. These measurements have been carried out to evaluate some important parameters, viz., apparent molar volume (φv), partial molar volume (φv0), transfer volume (φ0v (tr)), viscosity A and B coefficients of Jones-Dole equation, free energies of activation per mole of solvent (△μ0#1) and solute (△μ0#2),enthalpies (△H*) and entropies (△S*) of activation of viscous flow, variation of B with temperature ((a)B/(a)T)P, and molar refractive index (RD). These parameters have been interpreted in terms of solute-solute and solute-solvent interactions and structure making/breaking ability of solutes in the given solution. 相似文献
43.
Inrecentyears,attemptshavebeenmadetostudythephysico- chemicalbehaviorofaminoacidsinaqueous[1]aswellasaqueous- electrolyte[2], carbohydrate[3], and surfactant[4] media. Amino acids (AAs) are the basic components of proteins and are considered to be one of … 相似文献
44.
Basharat S Carmalt CJ King SJ Peters ES Tocher DA 《Dalton transactions (Cambridge, England : 2003)》2004,(21):3475-3480
The donor-functionalised alkoxides [Et(2)Ga(OR)](2)(R = CH(2)CH(2)NMe(2)(1), CH(CH(2)NMe(2))(2)(2), CH(2)CH(2)OMe (3), CH(CH(3))CH(2)NMe(2)(4), C(CH(3))(2)CH(2)OMe (5)) were synthesised by the 1:1 reaction of Et(3)Ga with ROH in hexane or dichloromethane at room temperature. Reaction of Et(3)Ga with excess ROH in refluxing toluene resulted in the isolation of a 1:1 mixture of [Et(2)Ga(OR)](2) and the ethylgallium bisalkoxide [EtGa(OR)(2)](R = CH(2)CH(2)NMe(2)(6) or CH(CH(3))CH(2)NMe(2)(7)). X-ray crystallography showed that compound 6 is monomeric and this complex represents the first structurally characterised monomeric gallium bisalkoxide. Homoleptic gallium trisalkoxides [Ga(OR)(3)](2) were prepared by the 1:6 reaction of [Ga(NMe(2))(3)](2) with ROH (R = CH(2)CH(2)NMe(2)(8), CH(CH(3))CH(2)NMe(2)(9), C(CH(3))(2)CH(2)OMe (10)). The decomposition of compounds 1, 4, 5 and 8 were studied by thermal gravimetric analysis. Low pressure CVD of 1 and 5 resulted in the formation of thin films of crystalline Ga(2)O(3). 相似文献
45.
ALI Anwar SABIR S. SHAHJAHAN HYDER S. 《物理化学学报》2007,23(7):1007-1012
Densities(ρ)and refractive indices(nD)of glycine(Gly),DL-alanine(Ala),DL-valine(Val)(0.02,0.04,0.06,0.08,and 0.10 mol·L-1)in 0.005 and 0.008 mol·L-1 aqueous cetyltrimethylammonium bromide(CTAB)have been measured at 298.15,303.15,308.15,and 313.15 K.The density data have been utilized to calculate apparent molar volumes(φv),partial molar volumes(φ0v),at infinite dilution and partial molar volumes of transfer φ0v(tr)of amino acids.The refractive index data have been used to calculate molar refractivity(RD)of amino acids in aqueous cetyltrimethylammonium bromide.It has been observed that φ0v varies linearly with increasing number of carbon atoms in the alkyl chain of amino acids,and hence,was split to get contributions from the zwitterionic end groups(NH 3,COO-)and methylene group(CH2)of the amino acids.The behaviour of these parameters has been used to investigate the solute-solute,solute-solvent interactions and the effect of cetyltrimethylammonium cation on these interactions. 相似文献
46.
LIAKATH ALI KHAN F. SIVAGURUNATHAN P. MEHROTRA S. C. 《物理化学学报》2007,23(5):709-712
The dielectric relaxation measurements on binary mixtures of esters (methyl acrylate, ethyl acrylate, and butyl acrylate) with phenol derivatives (p-cresol, p-chlorophenol, and 2,4-dichlorophenol) were carried out at different concentrations at 303 K using the time domain reflectometry (TDR) over the frequency range from 10 MHz to 20 GHz. The Kirkwood correlation factor and excess inverse relaxation time were determined and discussed to yield information on the molecular interactions of the systems. The relaxation time increased with increasing concentration of phenols and increasing chain length of esters. The excess inverse relaxation time values were negative for all the systems, which indicated the solute-solvent interaction existing between esters and phenols producing a field in such a way that the effective dipole rotation was hindered. 相似文献
47.
KABIR-UD-DIN ALI Mohd. Sajid KHAN Zaheer 《物理化学学报》2008,24(5):810-816
Kinetics of D-mannose oxidation by cerium (IV) was studied in a sulfuric acid medium at 40℃ both in absence and presence of ionic micelles. In both cases, the rate of the reaction was first-order in D-mannose and in cerium(Ⅳ), which decreased with increasing [H2SO4]. This suggested that the redox reaction followed the same mechanism. The reaction proceeded through formation of an intermediate complex, which was proved by kinetic method. The complex underwent slow unimolecular decomposition to a free radical that reacted with cerium (Ⅳ) to afford the product. The catalytic role of cationic cetyltrimethylammonium bromide (CTAB) micelles was best explained by the Menger-Portnoy model. The study of the effect of CTAB also indicated that a negatively charged species was reactive form of cerium (Ⅳ). From the kinetic data, micelle-cerium (Ⅳ) binding and rate constants in micellar medium were evaluated.The anionic micelle of sodium dodecyl sulfate plays no catalytic role. The oxidation has the rate expression --d[Ce(Ⅳ)]= k1Kcl[D-mannose] [Ce(Ⅳ)]dt Different activation parameters for micelle catalyzed and uncatalyzed paths were also calculated and discussed. 相似文献
48.
Different alcohols were formylated by formic acid under solvent-free conditions in the presence of iodine as the catalyst with good-to-high yields at room temperature. I2 generated in situ from Fe(NO3)3·9H2O/NaI also catalyzed the formylation of the alcohols under solvent-free conditions. This gives a green and efficient reaction at room temperature, in which the use of toxic and corrosive molecular I2 is avoided. 相似文献
49.
We present an ab initio density-functional theory study of PdH x systems. We evaluated the total energy of PdH x systems with the H atoms occupying interstitial (octahedral and tetrahedral) sites of a Pd supercell, allowing for the relaxation of the coordinates and supercell dimensions. The majority of our calculations were based on supercells consisting of four Pd atoms, and up to four H atoms, covering the range from x = 0.25 to x = 1. In addition some larger calculations are reported. In order to compare the relative stability of systems at different values of x (at fixed pressure and temperature T = P = 0), we computed the enthalpy of formation ΔH f (x) of the (non)stoichiometric systems. In the regime x = 0 → 1, the ΔH f (x) decrease in a manner indicative of the existence of attractive interactions between the dissolved H atoms. Ideal-solution theory cannot be applied to this system. Furthermore, we find that tetrahedral occupation is favoured over octahedral occupation at high x, leading to the formation of a zincblende structure at x = 1. A preliminary vibrational analysis of normal modes has been performed. Inclusion of vibrational zero-point energies in a harmonic approximation leads us to conclude, tentatively, that the observed stability of octahedral site occupation is due to more favourable zero-point energies of the H atoms in those sites. The results indicate that a proper understanding of this system must take into account the quantum nature of the dissolved hydrogen. 相似文献
50.
Spherulites of holmium tartrate trihydrate and holmium nitro-tartrate monohydrate have been grown in silica gel medium by
making holmium nitrate to react with tartaric acid at high supersaturations. The mechanism of spherulitic growth of holmium
tartrates is discussed. The spherulitic crystallization is shown to be due to heterogeneous nucleation. In the early stages
of growth an amorphous spherical mass gets nucleated inside the gel. Crystal fibers diverge radially from the surface of the
spherical mass giving rise to a spherical polycrystalline holmium tartrate. Thermal stability of the two types of spherulites
grown in the silica gel shows that the holmium tartrate trihydrate is more stable than holmium nitro-tartrate monohydrate.
The surface morphology and internal structure of the spherulites of holmium tartrates have been studied by using scanning
electron microscopy. The results on growth kinetics are given by studying the variation of radius of spherulites as a function
of time. A non-linear time–size relations under several conditions of growth have been observed, which suggests a non-uniform
solute concentration at the crystal surface. 相似文献