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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: OrgoDownfall on April 19, 2010, 08:49:47 PM

Title: Dehydration
Post by: OrgoDownfall on April 19, 2010, 08:49:47 PM

What reactant is dehydrated to make methylenecyclohexane (http://en.wikipedia.org/wiki/Methylenecyclohexane) and water? Methylenecyclohexane is the only product. The reaction has a proton to act as an electrophile.

I'm ok with hydrations of organic compunds, but I don't how to work backwards...

Any tips or help? Thanks a lot.

Title: Re: Dehydration
Post by: nj_bartel on April 19, 2010, 08:54:57 PM

It's an alcohol.

Title: Re: Dehydration
Post by: OrgoDownfall on April 19, 2010, 09:02:09 PM

Would it be a diol?

Title: Re: Dehydration
Post by: zanethan on April 20, 2010, 12:56:41 AM

I think it would be a terminal alcohol.  Via an E2 mechanism the OH will turn into H2O and leave forming a double bond.

Title: Re: Dehydration
Post by: OrgoDownfall on April 20, 2010, 09:19:17 PM

Can you treat working with dehydrations, the same as working backwards on hydrations?

So, I am getting 1-methyl-1-cyclohexanol if that's the case, but this is the major product. There can also be a minor product which would make this wrong.  :-[

I don't know how to go about this, and thanks zanethan, but I haven't learned E2 mechanisms... Any pointers or advice would be greatly appreciated. Thank you.

Title: Re: Dehydration
Post by: Doc Oc on April 21, 2010, 10:26:43 AM

Are you certain you haven't learned E2 eliminations?  It doesn't seem like you could answer this question without knowing eliminations.

Yes, you can look at dehydrations as backwards hydrations.  That might help you answer this question.  Starting with the given alkene, add H3O+ and see what products are possible.  That should point you in the right direction.

nj_bartel and zanethan are right, you just need to put the pieces together.  No, it's not a diol.