R Molar refraction

R, = Molar refractivity of the solute, and R2 = Molar refractivity of the solvent. 

The subset of compounds showing activity LC5q< 5 ppm (all para substituted) were submitted to regression analysis. Plots of log(l/LC5o) vs each physicochemical parameter (it, a, F, R, molar refractivity (MR), L, Bl, B4) (20) revealed several promising relationships, and it appeared that a was important although the 4-SCF3 compound was identified as an "outlier" in the analysis. (21)... 

R. Molar refractivity Directly proportional to electronic polarizability (see Section 31.1)... 

In SAR work, the biological activity of compounds is usually expressed by the values of IC50 or ED50. Physico-chemical properties used in SAR can be broadly classified into three general tjq)es electronic parameters, steric parameters and hydrophobic parameters. Electronic parameters include Hammett constants o ,(7, <7 ), Swain and Lupton field parameter (F), Swain and Lupton resonance parameter (R), etc. Steric parameters include Taft s steric parameter (Eg), molecular volume (Vm), molecular surface area (Area), molecular weight (MW), van der Waals radius (r), molar refractivity (MR), parachor (Pr), etc. Hydrophobic parameters include partition coefficient (LogP), distribution coefficient (LogD), substituent constant ( ), solubility... 

Now Pe is numerically equal to the molar refraction R which is an additive property. It has been shown that P is a property which can be calculated by adding the refractions of various electron groups. Six values for such partial molar refractions are given in Table 6.3. 

R v) is the molar refractivity of water, and (Rmw) is the molar refractivity of the methanol/water associate. 

In these equations, MR3 4, MR, and MR4 are the molar refractivities of 3- and 4-substituents, of R-, and of 4-substituents, respectively. All the equations exhibited positive coefficients of the MR terms. This suggests that the dispersion forces of substituents are actually responsible for the binding of ligands to cyclodextrin. Eq. 14 shows that the stability of a-cyclodextrin-RCOO complexes increases linearly up to MR = 4.0 and then falls off linearly. 

CMR represents the overall calculated molar refractivity. Its negative sign bring out a steric effect. It is interesting to note here that there is a high mutual correlation between ClogF and CMR (r= 0.966). Thus, it is very hard to predict for this data set if it is a negative hydrophobic or a polarizability effect. 

MRx is the calculated molar refractivity of X-substituents, whereas I is an indicator variable taking the value of 1 and 0 for the presence and absence of a phenyl ring in the X-substituents. The negative sign of MRx brings out a steric effect for the X-substituents that do not appear to reach a hydrophobic surface for ttx (calculated hydrophobicity of X-substituents), r = 0.470. The indicator variable (I) with positive coefficient suggests that the presence of a phenyl ring in the X-substituents would be favorable. 

A table of correlations between seven physicochemical substituent parameters for 90 chemical substituent groups has been reported by Hansch et al. [39]. The parameters include lipophilicity (log P), molar refractivity MR), molecular weight MW), Hammett s electronic parameters (a and o ), and the field and resonance parameters of Swain and Lupton F and R). 

From the measured refractive indices and densities for NaPSS in aqueous NaCl solution the molar refractivities and the apparent molar ion volumes were calculated. The following values were obtained R jaCl = 9.23 cm /mol, R O = 3.73 cnP/mol,... 

Interestingly, both specific refraction n and molar refraction (R), being temperature independent, should have the same values for a given substance either in the solid, liquid or gaseous state, provided the molecular structure is unchanged. 

Evidently, from Eq. (/ ), it is quite possible to determine the molar refractivity of an unknown solute Rj provided we know the mole fraction N, and N2 and the refractivities of the solute R2 and the homogeneous solution R, 2. 

Some of the properties of polymers derived from (NPC12)W and alanine152 and from arylamines153 have been described. The former are water-soluble and have potential medical applications. Molar refraction and volume data on NP(NHC6-H4R-p)2n (R = H, Me, OMe, or Cl) have been determined.154... 

The criterion propounded by Herzfeld in 1927 is instructive in understanding the metallic state. According to the Herzfeld criterion, a material is metallic when R/V I and insulating when R/V < 1. Here R is the molar refractivity of the atomic species in the gaseous state and V is the molar volume in the condensed state. This criterion explains the metallic character of the elements in nature (Edwards Sienko, 1983). Rao Ganguly (1986) have shown that the latent heat of vaporization provides a satisfactory criterion to delineate metallic elements from nonmetallic ones. 

Si1 The concept of oscillator strength was developed from the classical ffceory of dispersion. It is related to the molar refraction R of a substance... 

Greenshields and Rossini [8] derived equations for the molar refraction in analogy to eqs. 3.2.1 and 3.2.2. The following equation has been given to relate R of an alkane molecule to Pp of the corresponding n-alkane ... 

Waals volume-molar refraction approach, Bhattachaijee and Dasgupta [16] studied correlations between R d and the geometric volume for alkanes and haloalkanes. For alkanes (Ci-Cs), the following equation has been reported ... 

Bhatnagar, R. P., P. Singh, and S. P. Gupta, Correlation of van der Waals Volume with Boiling Point, Solubility and Molar Refraction. Indian J. Chem., 1980 19B, 780-783. 

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