Effects of Molecular Size and Structure on Self-Diffusion Coefficient and Viscosity for Saturated Hydrocarbons Having Six Carbon Atoms

Abstract

Self-diffusion coefficients and viscosities for the saturated hydrocarbons having six carbon atoms such as hexane, 2-methylpentane (2MP), 3-methylpentane (3MP), 2,2-dimethylbutane (22DMB), 2,3-dimethylbutane (23DMB), methylcyclopentane (McP) and cyclohexane (cH) were measured at various constant temperatures; obtained results were discussed in connection with their molar volumes, molecular structures and thermodynamic properties. The values of self-diffusion coefficients as the microscopic property were inversely proportional to those of viscosities as the macroscopic property. The order of their viscosities was almost same to those of their melting temperatures and enthalpies of fusion, which reflect the attractive interactions among their molecules. On the other hand, the order of the self-diffusion coefficients inversely related to the order of the melting temperatures and the enthalpies of the fusion. Namely, the compound having the larger attractive interaction mostly shows the less mobility in its liquid state, e.g., cyclohexane (cH), having the largest attractive interaction and the smallest molar volume exhibits an extremely large viscosity and small self-diffusion coefficient comparing with other hydrocarbons. However, a significant exception was 22DMB, being most close to a sphere: In spite of the smallest attractive interaction and the largest molar volume of 22DMB in the all samples, it has the thirdly larger viscosity and the thirdly smaller self-diffusion coefficient. Consequently, the dynamical properties such as self-diffusion and viscosity for the saturated hydrocarbons are determined not only by their attractive interactions but also by their molecular structures.

Dynamic Molecular Behavior of Semi-Fluorinated Oleic, Elaidic and Stearic Acids in the Liquid State

“…Reciprocal effective correlation time, 1/τ c , for the rotational movement of the each carbon atom, which is a semiquantitative measure of the segmental mostly rotational movement of the molecule, was evaluated from the obtained T 1 value, assuming that T 1 of protonated carbon is overwhelmingly dominated by dipole-dipole interaction with the attached protons 22 .…”

Lennard-Jones force field parameters for cyclic alkanes from cyclopropane to cyclohexane

“…Fig. 16 shows the present simulation results for the self-diffusion coefficient in comparison with experimental data [72][73][74][75][76][77], correlations thereof [62,78] and other simulation results [21,79]. It can be seen that the present cyclohexane model is able to describe the self-diffusion coefficient mostly within the scatter of experimental data.…”

“…Present simulation results (*) are compared with experimental data[72][73][74][75][76][77] (+), correlations[62] (-) and[78] (--) and other simulation results[21] (^) and[79] (&). The statistical uncertainties of the present simulation results are within symbol size.…”

Delaunay Simplexes in Liquid Cyclohexane

“…First, cyclohexane has density (0.773 g/cm 3 ), what is noticeably higher than density of all other noncyclic isomers. Note there are five such isomers (2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane and hexane), whose densities lie in a narrow interval from 0.645 to 0.659 g/cm 3 , where hexane has density 0.653 g/cm 3 , and 2,3-dimethylbutane -0.657 g/cm 3 (at room temperature) [18]. Until now there is no explanation of the high density of cyclohexane.…”