Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: Roju on 23/02/2016 12:38:52

Title: Does fehling's solution oxidize alcohols? Why not?
Post by: Roju on 23/02/2016 12:38:52
If not, how come it can oxidize aldehydes to carboxylic acids and not alcohols to aldehydes/ketones?

Does fehling's solution have any other use besides oxidizing and testing for aldehydes/reducing karbohydrates?

All input is appreciated :)
Title: Re: Does fehling's solution oxidize alcohols? Why not?
Post by: chiralSPO on 23/02/2016 16:47:02
Fehling's solution does not oxidize alcohols because the copper complex does not have enough oxidizing power to activate alcohols (maybe easily oxidized alcohols like benzyl alcohol or p-methoxylbenzyl alcohol or phenol might give false positives).

My suspicion is that under the alkaline aqueous conditions of the test, the aldehyde gets hydrated to an acetal, which is much more easily oxidized than an alcohol because there are two oxygens that can stabilize the carbocationic intermediate (vs just one with an alcohol). Ketones do not react because there is no hydrogen atom connected to the carbon at the center of a ketal. Note that formic acid and formate esters (possibly also formamides) will give a positive result as well, because they do have an oxidizeable carbon-hydrogen bond on the carbonyl center.