HYDROGEN-BOND SELF-ASSOCIATION AND CHEMICAL-REACTIVITY .2. RELATIONS BETWEEN HYDROGEN-BOND ASSOCIATION DEGREE AND ISOCYANATE-ALCOHOL REACTION-RATE

A cryoscopically calibrated H-1-NMR method for the determination of av erage hydrogen-bond ethanol self-association degree (f) in benzene (Bz ) and cyclohexane (Cy) at different temperatures was proposed. There i s a large difference between the reaction rate of phenylisocyanate (Ph NCO) with ethanol (EtOH) at the same concentration when the solvent Bz is replaced by Cy. The reaction rate constants are equal in both solv ents at the same magnitude of f. Synergetic effects in mixtures of hyd rogen reactive phyloisocyanic reactants (XH) were found. Urethanes exh ibit catalytic effects but only when the hydrogen atom is present at t he urethane nitrogen.