How acetaldehyde and acetone are distinguished using tollen`s test

Answer(i) Propanal and propanone can be distinguished by the following tests.(a) Tollen`s testPropanal is an aldehyde. Thus, it reduces Tollen`s reagent. But, propanone being a ketone does not reduce Tollen`s reagent. (b) Fehling`s testAldehydes respond to Fehling`s test, but ketones do not.Propanal being an aldehyde reduces Fehling`s solution to a red-brown precipitate of Cu2O, but propanone being a ketone does not. (c) Iodoform test:Aldehydes and ketones having at least one methyl group linked to the carbonyl carbon atom respond to iodoform test. They are oxidized by sodium hypoiodite (NaOI) to give iodoforms. Propanone being a methyl ketone responds to this test, but propanal does not. (ii) Acetophenone and Benzophenone can be distinguished using the iodoform test.Iodoform test:Methyl ketones are oxidized by sodium hypoiodite to give yellow ppt. of iodoform. Acetophenone being a methyl ketone responds to this test, but benzophenone does not.

Acetaldehyde gives a silver mirror to the “Tollen’s reagent” whereas ketones do not give a positive result for this test. Because, it can’t oxidize easily.

Tollens` reagent gives a negative test for most ketones, with alpha-hydroxy ketones being one exception. In reaction aldehydes form silver mirror. Ketones do not form silver mirror.