The Hydrolysis of p-Substituted Styrene Oxides

Based on a reasoned discussion of the following experimental data, propose a mechanism for the hydrolysis of substituted styrene oxides in acidic and basic media. 

A study of the hydrolysis of styrene oxide and its / -MeO, / -Me, p-C and /7-NO2 derivatives under aeidie (HsO and basic (OH ) conditions has been carried out. The experimental results obtained in flie study are as follows  

The expression of the rate constant for the hydrolysis of phenyl-substituted styrene oxides 1 to their corresponding glycols 2 is given by Eq. 11.1, where is the first-order rate constant for flie spontaneous (non-catalyzed) reaction, ka is the second-order rate constant for the hydronium ion-catalyzed reaction and is the second-order rate constant for the hydroxide-catalyzed reaction. 

The rate of hydrolysis of / -substituted styrene oxides in acidic medium is strongly affected by the nature of die substituent in the para position, varying from = 1-10x10 M s for die MeO substituent to = 3.41x10 M s in the case of the NO2 group. A plot of log An versus a for all / ara-substituents gives an excellent Hammed correlation widi a slope p = -A.l. 

The hydrolysis in H2 0 yields glycol products in which all of the 0 is incorporated into the benzyl hydroxyl group. 

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