Additivity of the partial molar volumes of organic compounds

Abstract

N o~i o NISH~MURA, TOHRU TANAKA, and TAKUSH~ MOTOYAMA. Can. J. Chem. 65, 2248Chem. 65, (1987. A critical test of additivity for partial molar volume has been made at 25' C in CCI4 with polyethylene glycol dimethyl ethers, crown ethers, cycloalkanes, n-alkanes, and others. Plots of partial molar volume at infinite dilution (v O ) against the properly chosen number of repeating unit ( n ) are linear except for small cyclic molecules, and the slopes of homologous straight chain and ring compounds are the same. The values of v O extrapolated to 11 = 0 for cycloalkanes and crown ethers support the validity of the contribution due to the translational kinetic energy that has been predicted recently on a theoretical basis. The importance of packing efficiencies around the solute molecules has been examined by means of simple models.NORIO NISHIMURA, TOHRU TANAKA et TAKUSH~ MOTOYAMA. Can. J. Chem. 65,2248Chem. 65, (1987. OpCrant i 25"C, dans des solutions de CC14, on a effectuC une Cvaluation critique de I'additivitC des volumes molaires partiels pour des Cthers dimtthyliques du polyCthylkne glycol, des Cthers couronnes, des cycloalcanes, des n-alcanes et d'autres composCs. A l'exception des molCcules contenant des petits cycles, on a trouvC qu'il existe une relation linCaire entre les volumes molaires partiels i dilution infinie (a O) et le nombre choisi appropriC d'unitts periodiques (n); de plus, les pentes des courbes pour les composCs homologues aliphatiques sont les mkmes que celles pour les composts cycliques. Pour les cycloalcanes et pour les Cthers couronnes, les valeurs de (v O ) extrapolCes i n = 0 sont en accord avec la prCdiction qui a rCcemment CtC faite sur une base thCorique et selon laquelle on pr6voit une contribution de la part de 1'Cnergie cinCtique de translation. Utilisant des moddes simples, on a CtudiC I'importance des efficacitCs d'empilement autour des moltcules de solutCs.[Traduit par la revue]

CHAPTER 8. Partial Molar Volumes of Non-Ionic Solutes at Infinite Dilution

“…A systematic study was performed by Edward and coworkers for several groups of solutes (hydrocarbons, alcohols, ethers, ketones, haloalkanes) in tetrachloromethane [39][40][41][42][43] and in benzene, ethanol, and cyclohexane. 44 Selected alkanes, cycloalkanes, aromatic hydrocarbons, haloalkanes, and ethers in tetrachloromethane were measured by Nishimura et al 45 Standard molar volumes on both sides of the concentration interval were evaluated for mixtures of ethers with tetrachloromethane. 46 Values for numerous n-alkanes and cyclic hydrocarbons in tetrachloromethane were summarised by Matteoli et al 47 Experimental standard molar volumes of derivatives of tetraphenylporphyrine along with the compiled extensive data for hydrocarbons and crown ethers in tetrachloromethane and for hydrocarbons, alcohols, and carboxylic acids in benzene were presented by Zielenkiewicz and Perlovich.…”

Conformational volume in statistics of chain molecules

“…Thus, the overali gauchetrans volume change reads3. lo) " = "intra + "pack (13) Of the two terms on the right-hand side of the last equation, the packing term can be even dominant. Recent statistical-mechanics computations ' I ) on butane yielding -2,62 cm3 * mol-' for Au at 291,5 K provide such an example.…”

“…This observation can be easily rationalized as a consequence of the effect of solvent (mainly due to the packing) on the volume increments Aui in a similar fashion as described above in Eq. (13).…”