Molecular volumes and surface areas

Geometric Examination. The polymer chemist needs to examine the various characteristics of the molecule in the molecular workspace. Bond lengths, bond angles and torsional angles can be measured for the current structure and compared to accepted values. In addition, other geometric properties can be computed like overall dimension, moments of inertia, molecular volume and surface area. 

Many groups have discussed the correlation between solubility and molecular properties [14-19], and the octanol/water partition coefficient, the molecular volume and surface area, the boiling point and charge distribution in the molecules are well-documented molecular descriptors that correlate strongly with experimental solubility. 

All current activity coefficient estimation models are by necessity semi-empirical in nature, because too little is known about solution theory for outright estimation. Chemical modeling is not readily available and is not far enough developed to make this type of calculation. The constants required by these models must be estimated using either experimental data (e.g. an infinite dilution activity coefficient or a molar volume) or group contributions derived from experimental data (e.g. interaction constants, molecular volumes and surface areas). 

Geometric/Biophysical Rotation axes, molecular volume and surface area... 

Aqueous Solubility of Polychlorinated Biphenyls Related to Molecular Structure This paper contains solubility data for 44 PCB congeners and outlines correlations with molecular volume and surface area. Several values are listed and referenced for most congeners. 

Water Solubilities of Polynuclear Aromatic and Heteroaromatic Compounds Water solubilities of polynuclear aromatic and heteroaromatic (oxygen, sulfur, and nitrogen) hydrocarbons have been compiled and evaluated and correlated with molecular volume, and surface area. 

Values for molecular volume and surface area used here were computed using the radii set and the numerical procedure described earlier [1], More recently. 

For each binary pair, there are two adjustable parameters that must be determined from experimental data, that is, (uy - ujj), which are temperature dependent. Pure component properties rl and ql measure molecular van der Waals volumes and surface areas and have been tabulated6. 

The surface of ACF of w = 1.45 nm was modified with molecular adsorption-decomposition method using SiCU. SiCU was adsorbed on the ACF and then hydrolyzed by introduction of H2O vapour at 298 K. Afterwards, residual SiCU and produced HCl vapours were removed, and then the treated ACF was heated at 573 K. The amount of the produced hydrated silica was determined by the measurement of the weight change. The micropore structure of the silica-coated ACF was examined by N2 adsorption the t-plot analysis of the N2 adsorption isotherm showed that the micropore width decreases with the silica coating by 0.2 nm the silica coating decreased the micropore volume and surface area from 1.49 ml/g and 2280 m /g to 0.68 ml/g and 1100 m /g, respectively. No spherical silica particles were observed on the external surface of the silica-coated ACF by scanning electron microscopy with a resolution of 10 nm. Therefore, hydrated silica should be deposited entirely on the micropore walls of the ACF. 

Here D is the molecular diffusivity of CO2, z is the film thickness, a, is the solubility of i, V and A are the volume and surface area of the ocean, and X is the decay coefficient. Use of pre-industrial mean concentrations gave a global boundary layer thickness of 30pm (D/z 1800m y = piston velocity). The film thickness is then used to estimate gas residence times either in the atmosphere or in the mixed layer of the ocean. For CO2 special consideration must be made for the chemical speciation in the ocean, and for " C02 further modification is necessary for isotopic effects. The equilibration times for CO2 with respect to gas exchange, chemistry, and isotopics are approximately 1 month, 1 year, and 10 years, respectively. 

In addition, it has been shown that the aqueous solubility of both PCB congeners and polynuclear aromatic hydrocarbons can be correlated with molecular volume that is not surprising since one would anticipate a relation between volume and surface area. 

Volume and surface area provide an elementary description of the molecular shape. For instance, a descriptor such as q = A(V) 2/3 can measure a degree of sphericity. The scaling behavior of q with a change in the van der Waals radii will be related to the surface s shape. Spheroidal surfaces should exhibit negligible scaling that is, q constant within a range of values of atomic radii. 

Micropore volumes (and hence densities) can be determined with some precision by gas sorption as such, it is possible to set a target density for simulations, thus addressing one of the most important variables in terms of predicting micropore volume. It is clear, however, that identical simulated densities can be obtained for materials with very different pore connectivities and, hence, different simulated accessible pore volumes and surface areas. An example of a molecular simulation for a hypercrosslinkedpolydichloroxylene network is shown in Fig. 1. 

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