Dehydration, acts on OH only or ketone too?

[Rach83]

On an a practice test, they say that Product A is treated with hot sulfuric acid which resulted in a dehydrated product B. The structure of Product B in the explanation shows that the OH group has been removed in the dehydration, but the double bonded O remains. I thought dehydration would also reduce this O to a single alcohol (OH)? No?
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Product A​

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[sleepy425]

no, I think you might be thinking of reduction. You reduce a ketone to get an alcohol. Dehydration in most contexts is just an elimination reaction with an alcohol

 

[Rach83]

no, I think you might be thinking of reduction. You reduce a ketone to get an alcohol. Dehydration in most contexts is just an elimination reaction with an alcohol

Oh I'm such an idiot. Clearly I can't get away with not reviewing O-chem especially when words like "dehydration" (obviously a loss of H20) doesn't ring a bell. 😱

Is it also possible to further reduce an alcohol?

Thanks for the reply sleepy.

 

[sleepy425]

Oh I'm such an idiot. Clearly I can't get away with not reviewing O-chem especially when words like "dehydration" (obviously a loss of H20) doesn't ring a bell. 😱

Is it also possible to further reduce an alcohol?

Thanks for the reply sleepy.

Well, it is possible to further reduce an alcohol (to an alkane), but direct reduction to an alkane is difficult and is not MCAT material. You can do a two-step reduction to an alkane by doing an elimination to an alkene and then catalytic hydrogenation to give an alkane.

Incidentally, reduction of an alcohol to an alkane is what you do when you want to make methamphetamine from pseduoephedrine. Methamphetamine is simply pseudoephedrine except that instead of a secondary alcohol that you have in pseudoephedrine, it's an alkane (methylene group) in methamphetamine. People who make meth usually use direct reduction methods (no, I don't make meth, but it's not hard to find out how they make it online).

 

[Rach83]

Thanks sleepy for the help (and for the interesting meth info)! You've saved me some time and I seem to be running out of that!