Benzyl alcohols, reactivity with phenyl isocyanate

Relatively little basic information has been published regarding the kinetics of phenol-formaldehyde intermediates, especially of phenols, methylol phenols, benzyl alcohol and benzylic ethers with isocyanates. Due to the fact that a typical resole contains both phenolic and benzylic hydroxyl groups, it was of interest to determine their reactivity toward isocyanates in the presence of various catalysts, as well as the effect of substitution on their reactivity. This investigation describes the kinetics of model phenols and model benzyl alcohols with phenyl isocyanate catalyzed with either a tertiary amine (dimethylcyclo-hexylamine, DMCHA) or an organotin catalyst, dibutyltin dilaurate (DBTDL) in either dioxane or dimethylformamide solution. 

The reactivity of the model phenols and benzyl alcohols with phenyl isocyanate was determined in the presence of a tertiary amine (DMCHA) and a tin catalyst (DBTDL) by measurement of the reaction kinetics. The experimental results based on initial equal concentrations of phenyl isocyanate and protic reactants showed that the catalyzed reactions followed second order reaction with respect to the disappearance of isocyanate groups (see Figure 1). It was also found that a linear relationship exists between the experimental rate constant kexp, and the initial concentration of the amine catalyst (see Figure 2). In the case of the tin catalyst, the reaction with respect to catalyst concentration was found to be one-half order (see Figures 3-4). A similar relationship for the tin catalyzed urethane reaction was found by Borkent... 

The effect of type of catalyst on the reactivity of phenol and benzyl alcohol with phenyl isocyanate can be seen in Table III. In the case of tertiary amine (DMCHA), there is a relatively small difference in the reactivity of both the phenol and benzyl alcohol with phenyl isocyanate. Using DBTDL as catalyst, benzyl alcohol was found to be 26 times more reactive than phenol in the reaction with phenyl isocyanate. 

EFFECT OF SUBSTITUTION ON REACTIVITY OF MODEL BENZYL ALCOHOLS WITH PHENYL ISOCYANATE IN DIOXANE AT 25°C... 

EFFECT OF CATALYSTS ON THE REACTIVITY OF PHENOL BENZYL ALCOHOL AND ETHYL ALCOHOL WITH PHENYL ISOCYANATE... 

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