Give simple chemical tests to distinguish between the following pairs of compounds:
Ethanal and Propanal
(i) Distinguish test between ethanal and propanal:
Iodoform Test: Ethanal gives iodoform test.
CH3CHO + 4NaOH + 3I2 → CHI3 (Yellow ppt.) + HCOONa + 3NaI + 3H2O
Propanal does not give this test.
CH3CH2CHO + 4NaOH + 3I2 → No Reaction.
Ethanal and propanal can be distinguished by iodoform test.
Aldehydes and ketones having at least one methyl group linked to the carbonyl carbon atom responds to the iodoform test. Ethanal having one methyl group linked to the carbonyl carbon atom responds to this test. But propanal does not have a methyl group linked to the carbonyl carbon atom and thus, it does not respond to this state.
`CH_3CHO + 3NaOI -> HCOONa + CHI_3 + 2NaOH`
Ethanal Sodium methanoate Iodoform(yellow ppt)