[Powerfool]

Hi. I got this problem wrong on a quiz and am trying to figure it out. The notes made in ink are possible answers.  Thanks for the help

[Powerfool]

Out of curiosity, how would one name this?

1,1-dimethyloxacyclohexane?
(we haven't gone over naming ethers except by common name)

[spirochete]

First off, reaction is under acidic conditions so you want to avoid negatively charged intermediates if possible.  And to make matters worse, one of your intermediates contains charge seperation.  Not to say that these things are absolutely impossible, but thinking about this problem there is definitely a more reasonable solution. 

The bromine radical idea is non sensical immediately because you don't have a suitable bond to generate a radical.  Bromine radical is generated from Br2 or NBS, neither of which are present in the problem. 

You are on the right track with the SN1 type mechanism, but we just don't need such a strong nucleophile for the reaction to go.  Is that a good hint?

[Powerfool]

Ok, I think I got it.




Is this correct?

[venkatjohnny]

Hi,
i think here one more problem is  why can't OH abstract proton since u r using acidic medium??

[sjb]

Out of curiosity, how would one name this?

1,1-dimethyloxacyclohexane?
(we haven't gone over naming ethers except by common name)

If you want to go down this sort of route, the oxygen is number 1, so 2,2-dimethyl-1-oxacyclohexane.

Alternatively, you might call it a substituted tetrahydropyran, so 2,2-dimethyltetrahydropyran.

[Gerard]

2,2-dimethyltetrahydropyran

i can imagine the horror of the exam!

[spirochete]

Hi,
i think here one more problem is  why can't OH abstract proton since u r using acidic medium??

I think what you're trying to say is why can't H20 accept a proton to make H3O+.  H20 certainly could, but you have work with what's given to you in the mechanism.  There are often multiple plausible possibilities for proton acceptors in organic reactions, and they are rarely critical to the overall mechanism.

Technically I believe abstraction refers to a radical process, for example in free radical bromination the bromine radical abstracts a hydrogen.  That's semantics though.

[Powerfool]

So, is this correct? (Ignore the extra carbon that magically appears in the carbocation, its supposed to be a tertiary carbocation I just drew it wrong.)

[spirochete]

yes that looks correct except for the extra -CH3 "typo"

[Powerfool]

yes that looks correct except for the extra -CH3 "typo"

Thank you for you help.