Molecular polarizability of organic compounds and their complexes: LIX. Molar volumes, intrinsic atomic solvation radii, and spatial structures of certain conformationally flexible compounds in solutions

The molar volumes and structures in individual liquids and solutions of a series of conformationally flexible compounds, such as alkanes and diaryl-substituted systems with sp ³-hybridized bridging atoms, were analyzed in terms of intrinsic solvation radii of atoms constituting the molecule. Intrinsic solvation atomic radii were determined for various molecules to show that they are larger than the van der Waals radii of the same atoms. An approach to parametrization of the intrinsic solvation radii of atoms constituting a molecule, using appropriate model compounds, was proposed. From the resulting values of intrinsic atomic solvation radii, the possible conformations of a series of diphenylmethanes, diphenylsilanes, diphenyl sulfides, diphenyl sulfoxides, and diphenyl sulfones in solutions were assessed.     

Molecular polarizability of organic compounds and their complexes: LII. Molar volumes of polymeric compounds in solutions,extrapolated to infinite dilution,and steric structure of their molecules

The molar volumes in solutions at infinite dilution were determined for a series of vinyl, glycol, isoprene, and cyclopentadiene polymers and oligomers with various degrees of polymerization. An additive analysis of the molar volumes showed that molecules of vinyl, ethylene glycol, and isoprene polymers exist in solutions in elongated helical conformations. In the majority of polymer molecules, except polystyrenes, polyisoprenes, and polycyclopentadienes, there are randomly disordered regions creating additional volumes inaccessible to solvation with solvent molecules. Cyclopentadiene oligomers formed by the Diels-Alder reaction have in solution the conformation of corrugated bands. The additive scheme for calculating the molar volumes considerably simplifies the determination of the dipole moments and Kerr constants of the compounds for which this scheme has been constructed.     

Molecular polarizability of organic compounds and their complexes: LI. Molar volumes and steric structure of intracomplex compounds in solutions at infinite dilution

Molar volumes in solutions at infinite dilution were determined for a series of intracomplex compounds of beryllium, zinc, cobalt, copper, and nickel, derived from salicyalalanilines, salicylalalkylimines, N-[(2-hydroxyphenyl)(methyl)methylene]anilines, N-[(2-hydroxyphenyl)(phenyl)methylene]aniline, as well as ethylene glycol and glycerol. An additivity scheme was constructed for calculation of the molar volumes of these compounds in solutions. Analysis of the experimental molar volumes of the systems studied showed that chelation via intramolecular complex formation almost always makes these values lower than those calculated by the additivity scheme, implying entropy stabilization of the chelates in solutions due to release of solvent molecules from the solvation shell of the molecules. It was shown that the dipole moments and Kerr constants of those compounds for which the additive scheme for calculation of molar volumes was constructed can be much easier estimated.     

Molecular polarizability of organic molecules and their complexes: LIV. Molar volumes of polyaryl organoelement compounds in solutions,extrapolated to infinite dilution,and steric structure of the molecules

Molar volumes in various solvents were determined for organic derivatives of silicon, phosphorus, arsenic, sulfur, and tellurium, containing aryl nuclei capable to internal rotation about single bonds between them and bridging groups. Additive analysis of the molar volumes of these compounds showed that the aryl nuclei are acoplanar with respect to the bridging groups. Most probable is a conrotatory mutual orientation of the aromatic rings. Molar volumes were also determined for a series of compounds with two bridging groups, which can serve as models of an extreme case of mutual proximity of aryl ring planes in diaryl systems with one bridging group. A possibility for considerably simplifying the methods for determination of dipole moments and Kerr constants for compounds whose molar volumes can be calculated by our developed additive scheme is demonstrated.     

Molecular polarizability of organic compounds and their complexes: LVI. Molar volume and structure in a solution of the compounds with several axes of intramolecular rotation

Molar volumes in solutions of compounds like orthoformic esters, trialkyl phosphates, trialkylphosphites, substituted aziridines, cyclopropanes, cyclohexanes, boroxines, N-aryl-4-pyridones, decalines, and cyclooctane were determined and discussed. Conformations of alkyl substituents in the esters were found to be similar to the conformations of the corresponding alkanes. Molar volumes of aziridines and cyclopropanes were found to be additive with respect to the molar volumes of bond and group increments. The nature of solvation of the molecules of these compounds was found to be similar to that in the model systems which served for the calculations of the increments. Molar volumes of cyclohexane, decaline, and cyclooctane also were found to be additive with respect to the contributions of the molar volumes of increments of the corresponding bonds and groups. The solvation and the steric structure of substituted boroxines were found to be similar to those of the structurally analogous substituted benzenes. Conformations of N-aryl-4-pyridone and its substituted derivatives in solutions were found to be similar to the conformations of biphenyl and its derivatives. A possibility of simplification of the methods for determining the dipole moments and Kerr constants of compounds from their additive molar volumes was demonstrated.     

Molecular polarizability of organic compounds and their complexes: L. Molar volumes and steric structure of some schiff bases and their structural analogs in infinitely dilute solutions

Molar volumes of a wide series of Schiff bases and their structural analogs, such as N-benzyl-ideneaniline N-oxides and azo compounds, in infinitely dilute solutions were determined. Analysis of the obtained values in terms of the additivity scheme showed that molecular fragments and substituting groups in these compounds are strongly solvated by solvent molecules, which leads to deviation of most molecules from the planar arrangement of the aryl moieties and bridging groups. Most compounds in which H-chelate rings are formed due to intramolecular hydrogen bonding are characterized by contraction of molar volumes, indicating their entropy stabilization in solution via release of solvent molecules from the solvate shell upon chelation. Methods for the determination of dipole moments and Kerr constants in solution can be simplified to a considerable extent for those compounds for which the additivity scheme was applied to calculate the molar volumes.     

Molecular polarizability of organic compounds and their complexes: LV. Molar volume and structure of some nitrogen compounds,their structural analogues,and some sterically hindered systems in solution

The molar volumes in solutions of a wide range of aliphatic and alicyclic amines, substituted acetanilides, 9- and 9,10-substituted anthracenes, and 1- and 1,8-substituted naphthalenes were estimated and discussed. Conformations of alkyl substituents in the aliphatic amines are similar to the conformations of the respective alkanes. Conformations (chair) of the molecules of alicyclic amines and cyclohexane are almost identical. In the molecules of acetanilides, the C(O)CH₃ group is conjugated with aromatic ring and is oriented toward the latter and toward the nitrogen of the amide group in the same manner as in acetophenone. A systematic decrease in the values of the molar volume increments of the substituents R in going from substituted benzene to substituted naphthalene and anthracene was revealed, which indicates the extension of the π-systems over the C-R bond. The orientation of 1,8-substituents relative to the naphthalene ring was found to be approximately orthogonal. A possibility to simplify the methods for determining the dipole moments and Kerr constants of compounds on the basis of their additive molar volumes was demonstrated.     

Molecular Polarizability of Organic Compounds and Their Complexes: XLVIII. Molar Volumes of Benzene Derivatives in Solutions at Infinite Dilution,Their Additivity,and Correlation with the Dipole Moments and Kerr Constants

Extrapolation formulas were derived for determination of the molar volume of a solute at infinite dilution. This quantity is stable to solvent replacement and additive with respect to increments of substituents in polysubstituted benzenes. The molar polarization and molar Kerr constant of a solute can be expressed through the molar volumes of the solute at infinite dilution and of the solvent. Replacement of the molar volume in the calculation formulas by the quantity calculated by the additive scheme considerably reduces the experimental time required for determining the dipole moments and Kerr constants of compounds in solution.     

Relationships between the molar volumes of mixtures of elements and their compounds

The molar volumes of stoichiometric mixtures of Group I–III metals and Group V–VII nonmetals are compared with the molar volumes of MX compounds. The derivatives of the B-subgroup metals have the molar volumes larger than the mixtures. The compounds of A-subgroup metals have smaller volumes than the mixtures. A crystal-chemical interpretation of this fact is advanced.     

Volumetric Properties of the Binary System Trihexyltetradecylphosphonium Bromide (CYPHOS IL 102) + N,N-Dimethylformamide (DMF) at Temperatures from T=293.15 to 313.15 K at Atmospheric Pressure

Volumetric properties for the trihexyltetradecylphosphonium bromide (CYPHOS IL 102) + N,N-dimethylformamide (DMF) binary system were determined at temperatures from T=293.15 to 313.15?K and ambient pressure (p=0.7 atm). Densities were measured by means of a vibrating tube densimeter (VTD). These measurements covered the full range of compositions along with the pure compounds; expansion coefficients, excess molar volumes, and partial molar volumes were calculated from the experimental densities. Excess molar volumes were fitted to a Redlich?CKister type equation. The excess molar volumes exhibit negative deviations from ideal behavior.     

Thermodynamic properties of binary mixtures containing sulfur amide: 3. Excess molar volumes of benzyl alcohol + N,N-dimethylmethanesulfinamide, + N,N-dimethylbenzenesulfinamide and + dimethyl sulfoxide

Excess volumes have been determined over the entire composition range for benzyl alcohol + N,N-dimethylmethanesulfinamide, + N,N-dimethylbenzenesulfinamide and + dimethyl sulfoxide at 303.06 and 323.21 K. The excess molar volumes are negative for all three systems, corresponding to the tendency of sulfinyl compounds to form hydrogen-bonded complexes with benzyl alcohol.     

Drude polarizable force field for aliphatic ketones and aldehydes,and their associated acyclic carbohydrates

The majority of computer simulations exploring biomolecular function employ Class I additive force fields (FF), which do not treat polarization explicitly. Accordingly, much effort has been made into developing models that go beyond the additive approximation. Development and optimization of the Drude polarizable FF has yielded parameters for selected lipids, proteins, DNA and a limited number of carbohydrates. The work presented here details parametrization of aliphatic aldehydes and ketones (viz. acetaldehyde, propionaldehyde, butaryaldehyde, isobutaryaldehyde, acetone, and butanone) as well as their associated acyclic sugars (d-allose and d-psicose). LJ parameters are optimized targeting experimental heats of vaporization and molecular volumes, while the electrostatic parameters are optimized targeting QM water interactions, dipole moments, and molecular polarizabilities. Bonded parameters are targeted to both QM and crystal survey values, with the models for ketones and aldehydes shown to be in good agreement with QM and experimental target data. The reported heats of vaporization and molecular volumes represent a compromise between the studied model compounds. Simulations of the model compounds show an increase in the magnitude and the fluctuations of the dipole moments in moving from gas phase to condensed phases, which is a phenomenon that the additive FF is intrinsically unable to reproduce. The result is a polarizable model for aliphatic ketones and aldehydes including the acyclic sugars d-allose and d-psicose, thereby extending the available biomolecules in the Drude polarizable FF.     

Partial molar volumes of l-alanine,dl-serine,dl-threonine,l-histidine,glycine, and glycylglycine in water,NaCl, and DMSO aqueous solutions at T = 298.15 K

The apparent molar volumes of l-alanine, dl-serine, dl-threonine, l-histidine, glycine, and glycylglycine in water and in the aqueous solutions of NaCl and DMSO with various concentrations at T = 298.15 K have been measured by the precise vibrating-tube digital densimeter. The calculated partial molar volumes at infinite dilution have been used to obtain corresponding transfer volumes from water to various solutions. The experimental results show that the standard partial molar volumes of the above amino acids and peptide at the dilute DMSO aqueous solutions are very close to those in water. However, the volumes show several types of variations with the increase of the concentrations of DMSO due to different types of side chain of amino acids, which should be discussed specifically. The NaCl changes considerably the infinite dilution standard partial molar volumes of the above amino acids and peptide in the aqueous solutions. The infinite dilution standard partial molar volumes of the each amino acids and peptide increase with the concentrations of NaCl. The experimental results have been rationalized by a cosphere overlap model.     

Volumetric properties of tetraphenylporphine,their metallo-complexes and some substituted tetraphenylporphines in benzene solution

Densities, apparent molar volumes and partial molar volumes of benzene solutions of tetraphenylporphine, H₂TPP, tetraphenylporphine metallo-complexes, MTPP (where M=Ni,Cu,Zn,Pd,Ag, and Cd), and some substituted tetraphenylporphines H₂T(i-R)PP (where i=2–4 and R=–Cl,–CH₃,–OCH₃) H₂T(i-F)PP (where i-2,3), H₂T(3-Br)PP, and H₂T(3-I)PP were determined at 25°C. It was found that the partial molar volumes of the studied compounds correlate linearly with the first ionization potential of the corresponding metal atom. The calculated values of the surface and volume accessible to the solvent, and the solvent-excluded volume for different conformations of H₂TPP, were compared with experimental data. The volume per molecule for different crystalline forms of H₂TPP and MTPP were compared with the partial molar volumes of the corresponding compounds in benzene solutions. The correlation between the partial molar volumes of H₂T(3-R)PP and their Van der Waals volumes are presented for R=–H, –F,–CH₃,–Cl,–Br,–OCH₃, and –I. The experimental data are rationalized in terms of differences in the conformational states of the molecules.     

Direct Evaluation of Partial Molar Volumes of Binary Solutions of Dimethyl Sulfoxide with Ethyl Acrylate,Butyl Acrylate,Methyl Methacrylate and Styrene

The Tikhonov regularization is applied to convert specific molar volume data of binary solutions of dimethyl sulfoxide with a number of acrylates and with styrene into their second- and first-partial derivatives with respect to mole fraction under constant temperature and pressure. Generalized Cross Validation is used to guide the selection of the regularization parameter that keeps noise amplification under control. The resulting first derivative is then used to compute the partial molar volumes. These are compared against that obtained by the traditional method of least-squares fitting of excess molar volumes. Some of the advantages of the current approach and possible extension to other partial molar quantities are briefly discussed.     

Excess molar volumes of methylcyclohexane+benzene, +methylbenzene, +1,4-dioxane,and +tetrahydrofuran at 303.15 K

Excess molar volumes V_m^E as function of mole fraction x for methylcyclohexane + benzene, + methylbenzene, + 1,4-dioxane, and + tetrahydrofuran are reported at 303.15 K. The excess molar volumes are positive and indicate the presence of weak interactions.     

Thermochemistry of aqueous solutions of nucleic acid bases and their alkylated derivatives

Enthalpy of solution, ΔH _sol ^o , enthalpy of sublimation, ΔH _subl ^o , apparent partial molar volume and heat capacities,V ₂ ^o andC _p,2 ^o were determined for aqueous solutions of thirty alkylated derivatives of uracyl and adenine, eight derivatives of cytosine and guanine. Calculated accessible surface areas and molar volumes are presented, too. The values of enthalpy of solution, enthalpy of sublimation can be useful in the studies on the nature of interaction between these compounds and water molecules. Apparent partial molar volume and heat capacity give a new aspect on hydrophob properties of the examined nucleic acid base derivatives.     

Molecular polarizability of the organic substances and their complexes: LX. Molecular volume and spatial structure of the series of heterocycles, their structurally nonrigid derivatives, and chromium tricarbonyl π-complexes in solutions

We have analyzed the molar volumes and structures in solutions of a series of azines, azoles, conformationally nonrigid bis(2-substituted benzimidazol-1-yl)methanes, and chromium tricarbonyl complexes of arenes. For most of the compounds, the rules of molar volume additivity with respect to the bonds and groups increments hold. Molecules of bis(2-substituted benzimidazol-1-yl)methanes exist in the form of conrotatory comformers with aryl fragments being out of the plane of bridging NCN bond angle. Strong linear correlations between the molar volume and molar refraction have been revealed within the studied compounds classes. In the case of chromium tricarbonyl complexes of arenes, the coordination bond polarity has increased with growing π-donor ability of the ligand, the molar volume increment of Cr(CO)₃ has increased as well, due to transfer of π-electron density from the ligand. The simplification of dipole moment and Kerr constant determination has been demonstrated.     

Molecular polarizability of organic compounds and their complexes: LIII. Molar volumes in solutions and steric structure of molecules of polyaryl compounds with bridging groups containing sp 2-and sp 3-hybridized carbon

The molar volumes of polyphenylmethanes, polyarylethanes, polyaryl compounds based on pyridinium cations, polyarylethylenes, and also diaryl and hetaryl ketones in various solvents were determined. Additive analysis of the molar volumes of these compounds showed that the aryl rings in their molecules are acoplanar to the bridging groups in which these rings can rotate about single bonds. The most probable is the conrotatory model of mutual orientation of the aromatic rings relative to each other. This orientation is similar to that found previously in solutions of such molecules as diphenylmethane, benzophenone, and some others, according to data of various physical methods. The possibility of substantial simplification of methods for determining the dipole moments, Cotton-Mouton constants, and Kerr constants for the compounds under consideration was demonstrated.     

Thermodynamic investigations on derivatives of pyrimidine nucleic acid bases: Joint use of calorimetric, volumetric and structural data for the description of properties of pyrimidine nucleic acid bases and their derivatives

The experimental enthalpies of solution Δ_solH_m^∞, van’t Hoff enthalpies of sublimation Δ_s^gH_m⁰ of solid compounds, partial molar volumes V₂⁰, and partial molar heat capacities C_p,2⁰ of aqueous solutions of pyrimidine nucleic acid bases and their derivatives, determined previously and collected here, are discussed in terms of calculated structural parameters. Relations have been established between the calorimetric and volumetric properties. Correlations have been developed to relate both the enthalpies of solvation and the partial molar heat capacities to the polar and apolar parts of the accessible molecular surface areas.