Molecular Complexes between Chloranil and Benzoic Acids in different Solvents and Application of the Hammett Equation

Department of Chemistry, F. C. College, Diamond Harbour-743 311

Department of Chemistry, Kalyani University, Kalyani-741 235

Manuscript received 20 December 1993, revised 22 July 1994, accepted 27 July 1994

Stability constants for the molecular complexes of chloranil with benzoic acid and substituted benzoic acids in aliphatic hydrogen bonded solvent CHCI₃ and aromatic aprotic solvent C₆H₆ have been determined. The stability constants of the substituted benzoic acid complexes have been found to be greater in CHCl₃ compared to those in C₆H₆ though the reverse has been found to be true for benzoic acid complex. The changes in the stability constant with solvents can not be properly interpreted but it is likely that dispersion forces are mainly responsible for the changes in the stability constant with solvent systems.

Correlation of the stability constants in terms of the Hammett equation has been found to be poor but the reaction solvent parameter (ῤ) has been found to be positive and negative respectively for CHCI₃ and C₆H_6, indicating that the aliphatic hydrogen bonded solvent and aromatic aprotic solvent act in a different way.