PRESSURE EFFECT AND MECHANISM IN THE ACID-CATALYZED HYDRATION OF PROPYLENE AND ISOBUTYLENE

The effect of pressure LIP to 3 lcbar on the rate of the acicl-catalyzecl hydration of propylene and isobutylene has been measured. 'The volumes of activation are: for propylene at 100' C -9.6 A -1.0 cm3 mole-', and for isobutylene at 35" C -11.5 A -1.0 cm3 mole-'. The effect of temperature in the range 90-120" C 011 the rate of hydration of propylene at 100 bar was measured. At 100" C the Arrhenius energy is 27.1 A -1.0 lccal mole-' and the entropy,of activation is -5.4 A -2.5 cal deg-' mole-'. Both the volumes and entropies of act~vat~on strongly indicate that a molecule of water is present in the transition states, which can therefore be represented as [olelin.H+.H?O!'. 'I'here appears to be no strong evidence regarding the molecular structure of the transition states.

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