Determination of H̲ acidity function for glycolic sodium glycoxide by use of t-butylphenols as indicators and a comparison with that found by use of amine indicators

Abstract

An H acidity scale, (H)_Ph^EG, for solutions of sodium glycoxide in ethylene glycoxide in ethylene glycol (EG) has been set up at 25 °C by use of t-butylphenols as indicator acids (HA). The value of H in this scale at a particular glycoxide concentration is lower than the corresponding value in the H scale, (H)_Am^EG, set up earlier for the same system with nitroanilines and -diphenylamines as indicator acids (HA). In a bid to understand the observed differences in the two H values activity coefficients (f_HA) of a typical neutral phenol as well as an amine indicator in glycoxide solutions of increasing concentration in glycol (glycol being taken as the standard state) have been determined by solubility and partition experiments respectively. An attempt has been made to explain the observed variation of f_HA as a function of glycoxide concentration and to understand the corresponding variation of the activity coefficients of the anions (f_A–) of the amine and phenol indicators in these solutions.