[quadsofdgods]

I was going over my notes(teacher made) and found that clemmensen reduction will also work on alcohols.
As far as i know it only works on aldehydes and ketones, even after extensive net research and forum searching (http://www.chemicalforums.com/index.php?topic=35867.0) i couldnt find alcohol listed anywere.

Am i correct in saying R-OH would not be reduced by a clemmensen reduction? When a source i usually rely 100% on is wrong i start to doubt everything
the only way to reduce an alcohol to an alkane would be with HI / Red P as the catalyst?

[discodermolide]

I was going over my notes(teacher made) and found that clemmensen reduction will also work on alcohols.
As far as i know it only works on aldehydes and ketones, even after extensive net research and forum searching (http://www.chemicalforums.com/index.php?topic=35867.0) i couldnt find alcohol listed anywere.

Am i correct in saying R-OH would not be reduced by a clemmensen reduction? When a source i usually rely 100% on is wrong i start to doubt everything
the only way to reduce an alcohol to an alkane would be with HI / Red P as the catalyst?

As far as I am aware alcohols are the product of such reductions!
R-OH to R-H make the halide and treat it with try-nButyltin hydride under radical conditions, or use a Barton de-oxygenation.

[james_a]

I was going over my notes(teacher made) and found that clemmensen reduction will also work on alcohols.
As far as i know it only works on aldehydes and ketones, even after extensive net research and forum searching (http://www.chemicalforums.com/index.php?topic=35867.0) i couldnt find alcohol listed anywere.

Am i correct in saying R-OH would not be reduced by a clemmensen reduction? When a source i usually rely 100% on is wrong i start to doubt everything
the only way to reduce an alcohol to an alkane would be with HI / Red P as the catalyst?

The way it's presented in textbooks, Clemmensen reduction is done under strongly acidic conditions with Zn amalgam (Zn-Hg). One common substrate is to have a ketone or aldehyde C=O adjacent to an aromatic ring being reduced to an alkane. Since it is strongly unlikely that both C=O bonds are reduced simultaneously, it is highly likely that the alcohol should be an intermediate en route to this product, since it will proceed in a stepwise fashion. One possible pathway is protonation of the alcohol to form R-OH2(+) followed by ionization to carbocation and then subsequent donations of  electrons from amalgam to give provide an extremely short lived anion (or organozinc) quickly protonated acid. Probably favored for benzylic ketones due to the stability of the benzylic carbocation (or alternatively, the benzylic radical).

As disco said, another way to reduce alcohol to alkane would be to convert alcohol to alkyl halide.... a different pathway to get the alkane would then be Mg or Li to make organometallic followed by acid.

[Nosterius]

The Clemmensen reaction is a good ol' textbook way to reduce ketones and aldehydes in an acidic media. It would seem that simple aliphatic alcohols are not intermediates during the reaction, since they cannot be reduced under the conditions.

However, benzylic and allylic alcohols can be reduced under Clemmensen reduction conditions. I would guess that these alcohols are converted first into the respective benzylic and allylic chlorides by the HCl, and then react with the zinc amalgam.

Reference: Strategic applications of named reactions in organic synthesis, by Laszlo Kurti and Barbara Czako (Elsevier)

[nox]

Since we're on the topic of deoxygenation...

Found a handy "note" in an old J. Chem. Soc. paper regarding the deoxygenation of benzophenones. (Note 272 by J. Blackwell and W. J. Hickinbottom, J. Chem. Soc., 1961, 1405-1407) Apparently you can burn off the carbonyl by refluxing for 30 minutes in an ether solution of LiAlH₄ and AlCl₃. Yields were apparently consistently around 90% for a wide variety of substituted benzophenones.

I'm tempted to try this, but not sure how reliable the prep is. Oh and also, the mechanistic aspects should also be interesting, I'm guessing it first gets reduced to the alcohol, which coordinates to AlCl₃, subsequent hydride delivery then cleaves the C-O bond and the carbonyl eventually gets turned into some sort of aluminum oxide.