Question

There are some compounds which are as follow:

1-phenyl-1-butene, 1-phenyl-2-butene, 2-phenyl-1-butene

Which of the following is the correct order for increasing order of reactivity for acid catalyzed hydration?

1) 1-phenyl-1-butene < 1-phenyl-2-butene < 2-phenyl-1-butene

2) 1-phenyl-2-butene < 1-phenyl-1-butene < 2-phenyl-1-butene

3) 2-phenyl-1-butene < 1-phenyl-2-butene < 1-phenyl-1-butene

Answer 1

The correct order of increasing reactivity towards acid-catalyzed hydration is:
1phenyl2butene< 1phenyl1butene< 2phenyl1butene . As the number of alkyl groups attached to the carbon atoms increases, the +I effect of the alkyl groups increases and the alkene becomes electron rich. Hence, the reactivity towards acid-catalyzed hydration increases as pi electrons of the double bond is donated to proton. Also as the stability of alkene decreases. (monosubstituted alkene is less stable than disubstituted alkene), The reactivity towards acid-catalyzed hydration increases.