Of the Hammett equation to heterocyclic

Applications of Linear Free Energy Relationships to Polycyclic Arenes and to Heterocyclic Compounds , M. Charton, in Recent Advances in Correlation Analysis in Chemistry , ed. N. B. Chapman and J. Shorter, Plenum, New York, 1978, pp. 175-268. Applications of the Hammett Equation to Heterocyclic Compounds P. Tomasik and C. D. 

It is now 13 years since the appearance of Volume 1 of Advances in Heterocyclic Chemistry, and significant progress in many of the subjects covered in the early volumes of the series has been made since publication. We have therefore embarked on the policy of updating appropriate chapters, and three of the articles in the present volume are of this type. Adrien Albert has written an account of the progress of covalent hydration since its first appearance in Volume 4. P. Tomasik and C. D. Johnson have reported on progress in the application of the Hammett equation to heterocycles since the Jaffe and Lloyd Jones article in Volume 3, and A. Holm has similarly taken on the account of 1,2,3,4-thiatriazoles given by Jensen and Pedersen in the same volume. 

Tomasik, P., Johnson, C. D., Applications of the Hammett Equation to Heterocyclic Compounds, 20, 1. 

Evaluation of steric effects can also be made by separating electronic from steric effects with the help of linear free energy relationship and appropriate parameters. Applications of the Hammett equation to heterocycles have been reviewed (64AHC(3)209 76AHC(20)1) and the influence of substituent effects on the basicity and N-alkylation of pyridines, which have been by far the most widely studied, shows the difficulties in this approach. Jaffe and Jones (64AHC(3)209) reported a good correlation between pKA of 3- and 4-substituted pyridines and Hammett a parameters ([Pg.179]

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