DISSOCIATION-CONSTANTS OF CHLOROGUAIACOLS IN WATER - A COMPARISON OF MEASURED AND PREDICTED VALUES

Chloroguaiacols are common components of bleached-kraft pulp mill effl uent known to bioaccumulate in aquatic organisms and to sorb on partic ulate material and sediments. Ionization properties of the chloroguaia cols must be known in order to explain their sorptive behavior in aqua tic systems. To obtain this information, thermodynamic acid dissociati on constants (pK(a)) of guaiacol (o-methoxyphenol) and nine chloroguai acols have been determined by spectrophotometric methods. These experi mental pK(a) values have been compared with literature values, values predicted by the Hammett equation, and predictions by quantum chemical calculations using MOPAC 6.0 with AM1 and MNDO Hamiltonian operators. Experimental and predicted acidities were strongly correlated, and th e correlation equations obtained have been used to calculate pK(a) val ues for those chloroguaiacols that were unavailable for experimental m easurement.