Refractivity, molecular bond refractions

Uric acid is odourless in spite of three carbonyl groups, four trivalent nitrogen atoms and a double bond, and that it is similarly colourless in spite of four chromophores. Measurements of its refractive and dispersive properties indicate that it is a saturated body which suggests that molecular attraction exists between the various groups. 

But by experimental determination the molecular refraction is found to be 48 71, which is 3-235 in excess of the value calculated from the atomic refractions. Two double bonds between carbon atoms would account for 3-414 in excess, so that it is evident that geraniol contains two such double linkages. No alcohol of the formula Cj HjgO with two double linkages can contain a ring, so that geraniol must belong to the open chain series, a conclusion entirely supported by its chemical characters. 

H-bonding is an important, but not the sole, interatomic interaction. Thus, total energy is usually calculated as the sum of steric, electrostatic, H-bonding and other components of interatomic interactions. A similar situation holds with QSAR studies of any property (activity) where H-bond parameters are used in combination with other descriptors. For example, five molecular descriptors are applied in the solvation equation of Kamlet-Taft-Abraham excess of molecular refraction (Rj), which models dispersion force interactions arising from the polarizability of n- and n-electrons the solute polarity/polarizability (ir ) due to solute-solvent interactions between bond dipoles and induced dipoles overall or summation H-bond acidity (2a ) overall or summation H-bond basicity (2(3 ) and McGowan volume (VJ [53] ... 

The general or universal effects in intermolecular interactions are determined by the electronic polarizability of solvent (refraction index n0) and the molecular polarity (which results from the reorientation of solvent dipoles in solution) described by dielectric constant z. These parameters describe collective effects in solvate s shell. In contrast, specific interactions are produced by one or few neighboring molecules, and are determined by the specific chemical properties of both the solute and the solvent. Specific effects can be due to hydrogen bonding, preferential solvation, acid-base chemistry, or charge transfer interactions. 

Exaltation. The amt by which the molecular refractivity of a compd exceeds the sum of the refractivities of its atoms it is an indication of constitution (presence of double bonds, etc)... 

The dipole moment of naphthazarin has been deduced from the measurements of the dielectric constants of its solutions in benzene and dioxan, respectively. A heterodyne beat apparatus has been used at 4 4 Mhz, the temperature of the solution was 20°C. The molecular refraction has been computed [8] from standard bond refractions, the experimental determination being impossible because of the strong... 

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