[hdieu]

Hello all,
I have a general problem that I can't seem to solve. Here's the information given:

Preparation of 3-phenyl-2-butanol by treatment of 3-phenyl-1-butene wit H2SO4 is unsatisfactory because 2-phenyl-butanol is obtained instead. Explain why this happens.

Any ideas? I don't see how this can happen. If this is an acid-catalyzed hydration reaction to an alkene, a proton would be added to the least substituted carbon of the double bond, yielding a secondary carbocation. A hydride shift from the adjacent carbon (that bonded to phenyl) would yield a benzylic/tertiary carbocation. This seems most energetically favorable, but it is not the case with the problem. Any help would be appreciated! Thanks!

[chrisf]

I can see why 3-phenyl-2-butanol is not formed - exactly what you stated.. a hydride-shift to make a tertiary carbocation. I'm also puzzled how they'd come up with 2-phenyl-1-butanol. Hmmm....

The only thing I can think of at the moment is steric hindrance by the phenyl group on that carbon - but even still, that'd make the original secondary carbocation more favorable, not the primary carbocation they're suggesting.

There must be some other rearrangement we're both missing.
hey

[chrisf]

What if the tertiary-alcohol was formed and then was dehydrated by excess acid.. and for some crazy reason the elimination didn't obey Zaitsev's Rule? :D Wait...
hey

[chrisf]

I'm still puzzled by this one. I tried to come up with some methyl-shift scenario.. but nothing makes sense other than what we both seem to agree upon.
hey

[kyle1990]

I've been thinking about this one for about a solid hour now...and yeah, i can't come up with a synthesis route either. I'm with Chris in the dehydration with excess acid, producing the minor product in which Zaitsev's Rule was not obeyed. But you would still need another reagent, like borane, to hydrate the alkene into a primary alcohol....this is very puzzling. I like it =)
hey

[chrisf]

But you would still need another reagent, like borane, to hydrate the alkene into a primary alcohol....this is very puzzling. I like it =)

Yeah, even if you had a Hoffman elimination you'd still need to put on an Anti-Markovnikov alcohol.

I really hope this person comes back to enlighten us (if/when he/she finds out the answer.)
hey

[kyle1990]

I really hope this person comes back to enlighten us (if/when he/she finds out the answer.)

I hope so too. I'm very curious about this one...
hey