US EPA

9837 

Journal Article 

Substituent constants for correlation analysis 

Hansch, C; Rockwell, SD; Jow, PYC; Leo, A; Steller, EE 

1977 

Yes 

Journal of Medicinal Chemistry
ISSN: 0022-2623
EISSN: 1520-4804 

20 

2 

304-306 

English 

836503 

10.1021/jm00212a024 

WOS:A1977CT63500024 

The use of substituent constants in the field of physical organic chemistry has had an enormous impact on the study of organic reaction mechanisms.1 3 The use of such constants has enabled us to delineate the role of substituents on organic and biochemical processes in terms of polar, resonance, steric,4 hydrophobic,” and polarizability vectors. There is a dichotomy between the fields of physical organic chemistry and biomedicinal chemistry in that interest in the former field centers on more and more precise definitions of electronic7 and steric constants in order to enable one to formulate sharper relationships in relatively well-defined homogeneous organic reactions. On the other hand, biomedicinal chemists need a great variety of substituent constants on a range and type of substituent far beyond the current interests of physical organic chemists. Moreover, the noise in the dependent variables with which the biomedicinal chemist is forced to work is so large that the quality of the substituent constants is not as critical as is the need for having the largest possible number of substituents parameterized. For this reason we have been collecting Hammett-Taft constants as well as hydrophobic constants from whatever source available. Table I contains constants on a miscellaneous set of substituents with which we became involved in correlation analysis and is an extension of our earlier compilation.6 All of the constants were determined in our laboratory from the benzene solute system, i.e., by partitioning X-C6H5 between octanol and water. Some of the constants were determined in our laboratory; others, as indicated, have been taken from the literature.