The apparent dissociation constants of N-(meta-substituted- phenyl) glycines have been determined by pH method at 15, 25, 35C in the pesence of 0.1M, NaClO4 and in 30% (vol.) ethanol solution. It was found that in the N-substituted phenyl glycine molecule, when the substituent has been changed from para position to meta position, the dissociation constants of these amino acids change appreciably. In addition, the thermodynamic parameters of protonation of N-(meta-substituted-phenyl) glycines were also calculated.

Key words: AMINO ACID, BENZAMINE P, ACETIC ACID P, DISSOCIATION EQUILIBRIUM