In terms of Domingo terminology, complexes of carbonyl compounds with imidazolium cations should be considered as extremely strong electrophiles. Reactions of these compounds with phenol yielding bis-phenols follow a polar mechanism. Furthermore, the discussion based on the theory of reactivity indexes can be used to predict the reactivity of respective electrophiles and regio-orientation in EAS reactions, the first stage of bis-phenol synthesis, kinetically rate-limiting for the whole process.