Tollens' test on Alpha hydroxy ketones

[Prabs3257]

Homework Statement

can all alpha hydroxy ketones give tollens test or only those in which hydroxy group is on the terminal carbon ??

Relevant Equations

Tautomerism

I know its because of tautomerism that they form an aldehyde group because of which they give the test but can all alpha hydroxy ketones give tollens test or only those in which hydroxy group is on the terminal carbon ??

 

[TeethWhitener]

This is kind of a tricky question. You are right that terminal alpha hydroxy ketones will tautomerize to aldehydes which are reactive with the Tollens reagent, and non-terminal ones don’t exhibit that tautomerism. However, from personal experience, non-terminal alpha hydroxy ketones also tend to be fairly straightforward to oxidize (to diones) under mild conditions. I’ve never tried oxidizing them specifically with Tollens’ reagent, but I know copper(II) will do the trick, so I can imagine silver(I) might as well. Normally, this would be a 5 minute experiment: I’d just walk into lab, whip up a batch of Tollens’ reagent, and toss in some benzoin, but these aren’t normal times and I don’t know when I’ll be able to get back into lab.
So you’re right in the tautomerism part, but it’s possible that the oxidation could still proceed through a different mechanism even with non-terminal alpha hydroxy ketones.