Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Conformational analysis of branched alkanes using limiting partial molar volumes

Barbosa, E. F. G.[Ester F.G.], Pereira, E. V.[Elsa V.], Santos, A. F. S.[Angela F.S.], Lampreia, I. M. S.[Isabel M.S.]
J. Chem. Thermodyn. 2017, 115, 84-90
ABSTRACT
The solvent effect on the solute conformations of straight and branched-chain alkanes infinitely diluted in methanol and carbon tetrachloride is studied. An additive scheme is used that takes into account the strong relation between limiting partial molar volumes and the average numbers of gauche conformations adopted by the solute molecules in each solvent. These numbers were determined using the Pitzer!|s steric partition function with different values of anti yengauche transition enthalpy variations, ranging from (+700 to -350) kcal*mol-1. The partial molar volumes at infinite dilution for three mono branched-chain alkanes (2-methylpentane, 3-methylpentane and 2-methylheptane) were experimentally determined in methanol to complement other series consisting mainly of straight, bi and tri branched-chain alkanes obtained in previous works. The conformational analysis performed using statistical methods is quite convincing about the strong effect of the solvent on the solute conformation equilibrium. Conclusions about close-packing and structure effects related to anti-gauche transitions in these two solvents are also drawn.
Compounds
# Formula Name
1 CH4O methanol
2 C8H18 2-methylheptane
3 C6H14 2-methylpentane
4 C6H14 3-methylpentane
5 C7H8 toluene
6 C7H16 heptane
Datasets
The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type Compound-# Property Variable Constraint Phase Method #Points
  • POMD
  • 1
  • Mass density, kg/m3 ; Liquid
  • Temperature, K; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Vibrating tube method
  • 1
  • POMD
  • 2
  • Mass density, kg/m3 ; Liquid
  • Temperature, K; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Vibrating tube method
  • 1
  • POMD
  • 3
  • Mass density, kg/m3 ; Liquid
  • Temperature, K; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Vibrating tube method
  • 1
  • POMD
  • 4
  • Mass density, kg/m3 ; Liquid
  • Temperature, K; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Vibrating tube method
  • 1
  • POMD
  • 5
  • Mass density, kg/m3 ; Liquid
  • Temperature, K; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Pycnometric method
  • 1
  • POMD
  • 6
  • Mass density, kg/m3 ; Liquid
  • Temperature, K; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Pycnometric method
  • 1
  • POMD
  • 3
  • 1
  • Mass density, kg/m3 ; Liquid
  • Molality, mol/kg - 3; Liquid
  • Pressure, kPa; Liquid
  • Temperature, K; Liquid
  • Liquid
  • Vibrating tube method
  • 16
  • POMD
  • 4
  • 1
  • Mass density, kg/m3 ; Liquid
  • Molality, mol/kg - 4; Liquid
  • Pressure, kPa; Liquid
  • Temperature, K; Liquid
  • Liquid
  • Vibrating tube method
  • 14
  • POMD
  • 2
  • 1
  • Mass density, kg/m3 ; Liquid
  • Molality, mol/kg - 2; Liquid
  • Pressure, kPa; Liquid
  • Temperature, K; Liquid
  • Liquid
  • Vibrating tube method
  • 11