Give simple chemical tests to distinguish between the following pairs of compounds
Propanal and Propanone
Propanal and propanone can be distinguished by the following tests.
Propanal is an aldehyde. Thus, it reduces Tollen’s reagent. But, propanone being a ketone does not reduce Tollen’s reagent.
`CH_3CH_2CHO + 2[Ag(NH_3)_2]^+ + 3OH^(-) -> CH_3CH_2COO^(-) + Ag darr + 4NH_3 + 2H_2O`
Propanal Tollen's regent Propanoate ion Siver mirror
Aldehydes 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.
`CH_3CH_2CHO + 2Cu^(2+) + 5OH^(-) -> CH_3CH_2COO^(-) + CH_3CH_2COO^(-) + Cu_2O darr + 3H_2O`
Propanal Propanoate ion Cuprous oxide(Red brown ppt)
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.
`CH_3COCH_3 + 3NaOI -> CH_3COONa + CHI_3 + 2NaOH`
Propanone Sodium aceatate Iodoform (yellow ppt)
Propanal and Propanone : These two are distinguished by the iodoform test.propanal does not give iodoform test when it reacts with I2 in the presence of NaOH while propanone give iodoform test when reacts with I2 in the presence of NaOH.
Video Tutorials For All Subjects
- Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Oxidation