Decane, molecular model

Fifjure 5.3. Comparison between (a) methane and (b) decane molecular models. 

Independent self-diffusion measurements [38] of molecularly dispersed water in decane over the 8-50°C interval were used, in conjunction with the self-diffusion data of Fig. 6, to calculate the apparent mole fraction of water in the pseudocontinuous phase from the two-state model of Eq. (1). In these calculations, the micellar diffusion coefficient, D ic, was approximated by the measured self-dilfusion coefficient for AOT below 28°C, and by the linear extrapolation of these AOT data above 28°C. This apparent mole fraction x was then used to graphically derive the anomalous mole fraction x of water in the pseudocontinuous phase. These mole fractions were then used to calculate values for... 

Monte Carlo and molecular dynamics calculations of the density profile of model system of benzene-water [70], 1,2-dichloroethane-water [71], and decane-water [72] interfaces show that the thickness of the transition region at the interface is molecu-larly sharp, typically within 0.5 nm, rather than diffuse (Fig. 4). A similar sharp density profile has been reported also at several liquid-vapor interfaces [73, 74]. The sharpness of interfaces thus seems to be a general characteristic of the boundary between two stable phases and it is likely that the presence of supporting electrolytes would not significantly alter the thickness of the transition region at an ITIES. The interfacial mixed solvent layer [54, 55], if any, would probably have a thickness comparable with this thin inner layer. 

When the actual van der Waals radius is used, two molecules are completely adsorbed. One surface of the model phase was further modified to study selectivity. In one case the surface was methylated and in another it was hydroxylated, as shown in Figures 3.7 and 3.8, where decane and anthracene are adsorbed, respectively. The relative molecular masses of the methylated and hydro>ylated adsorbents are 5096 and 5156, respectively. The methylated adsorbent is bent by the saturated methyl groups. 

An earlier suggestion of Fixman of how to mimic flexibility has been discussed with respect to a system with two degrees of freedom. Harmonic stretching and bending of the bonds of butane in liquid CCI4 has subsequently been allowed transition state theory does not exactly apply as many barrier crossings are reflected by solvent collisions. In a modified molecular dynamics examination of conformational isomerizations in butane the effect of solvent was expressed with a stochastic model in which the Newtonian trajectory was modified by random impulses. The frequency of these impulses, which have a frictional effect upon the trajectory, reduced the value of the transmission coefficient by inducing oscillatory motion at the col. At the inner bonds of decane isomerization rates are less than in butane. 

How sharp is the interfacial region between water and an organic liquid and what is its molecular structure Broadly, three possibilities should be considered (1) the interface is sharp and flat, as assumed in continuum models (2) the interfacial region is a mixture of the two liquids and (3) the interface is a locally sharp but rough surface that fluctuates in time. Recent computer simulations of interfaces between water and benzene, " decane, nonane, hexane, dodecane, 1,2-dichloroethane (DCE), CCU, and octanol have dealt with this issue. 

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