[matt105]

Hey guys. I've been studying for the ACS final for Organic Chemistry (Biochem major here). Anyway, I just ran into this problem in the study guide. I don't know why this reaction would not occur. Here is the question

"Which of these reactions would produce tert-butylbenzene in high yield?

It then lists 4 reactions, and I knew the first one would occur, it was an electrophilic substitution of benzene with tert-butylchloride and aluminum chloride. The fourth one I knew would occur. But I don't understand why the second one wouldn't occur, and why the third would occur.

Here is the second one:
The reagents are benzene, 2-chlorobutane, and AlCl3 (lewis acid). I know this would give a carbocation on the second carbon of the butane chain, but why wouldn't a 1,2-methyl shift occur to give a tert-butyl carbocation? Am I just working this out wrongly in my head? That could definitely be the case  Or maybe it just wouldn't occur enough for them to validate saying that it occurs in high yield?

here is the third one that I don't understand why it would occur.
Benzene, 2-methylpropanol, and H2SO4: Does the H2SO4 just protonate the alcohol, cause it to disscoiate, and that leaves a carbocation that rearranges to give tert-butyl carbocation?

Thanks for any help guys! And I apologize in advance for any incorrect terminology, but I believe I had all the names right.

edit: Sorry I forgot to mention that the answer was that the first, third, and fourth reaction would occur in high yield
Matt

[wereworm73]

For the 2nd one, a methyl shift would leave a positive charge on a primary carbon, which would make the carbocation unstable. 

As for the 3rd one, a hydrogen shift & loss of a water would leave you a stable t-butyl carbocation which can then electrophilically react with benzene.

[matt105]

Ok I dont know what I was thinking on the 2nd one. Too muh studying I guess, haha. The third one makes sense now, thanks.