HYDROGEN-BOND SELF-ASSOCIATION AND CHEMICAL-REACTIVITY .1 KINETIC-STUDY OF REACTIONS BETWEEN GLYCOLS AND PHENYLISOCYANATE

A method of following the kinetics of the uncatalysed reaction between glycols and phenylisocyanate by means of the High Performance Liquid Chromatography (HPLC) is proposed. The second-order equations can be u sed with enough good approximation to represent the addition process. The reaction rate constants of the two glycol OH groups are generally unequal, being strongly influenced by the eventual intramolecular hydr ogen-bonding. In strong polar solvents like N, N-dimethylformamide the differences between the reaction rate constants values tend to vanish . Rate constants for water, 1,2-ethane-, 1,3-propane-, 1,4-butane-, 1, 5-pentane-, 1,6-hexane-diols and diethylene glycol in different solven ts were determined. 1,4-Butanediol exhibits in benzene the highest rea ction rate constant in the first step of the reaction. Unexpected enha ncement of glycol reactivity, in benzene, appears in the presence of o ther alcohols or urethane molecules.