Question -
Answer -
(i) Propanal and Propanone
(ii) Acetophenone and Benzophenone
(iii) Phenol and Benzoic acid
(iv) Benzoic acid and Ethyl benzoate
(v) Pentan-2-one and Pentan-3-one
(vi) Benzaldehyde and Acetophenone
(vii) Ethanal and Propanal
Answer
(i) Propanaland propanone can be distinguished by the following tests.
(a) Tollen’stest
Propanal is an aldehyde. Thus, it reduces Tollen’sreagent. But, propanone being a ketone does not reduce Tollen’s reagent.
(b) Fehling’stest
Aldehydes respond to Fehling’s test, but ketones do not.
Propanal being an aldehyde reduces Fehling’ssolution to a red-brown precipitate of Cu2O, but propanone beinga ketone does not.
(c) Iodoformtest:
Aldehydes and ketones having at least one methyl grouplinked to the carbonyl carbon atom respond to iodoform test. They are oxidizedby sodium hypoiodite (NaOI) to give iodoforms. Propanone being a methyl ketoneresponds to this test, but propanal does not.
(ii) Acetophenoneand Benzophenone can be distinguished using the iodoform test.
Iodoform test:
Methyl ketones are oxidized by sodium hypoiodite to giveyellow ppt. of iodoform. Acetophenone being a methyl ketone responds to thistest, but benzophenone does not.
(iii) Phenoland benzoic acid can be distinguished by ferric chloride test.
Ferric chloride test:
Phenol reacts with neutral FeCl3 toform an iron-phenol complex giving violet colouration.
But benzoic acid reactswith neutral FeCl3 to give a buff coloured ppt. of ferric benzoate.
(iv) Benzoicacid and Ethyl benzoate can be distinguished by sodium bicarbonate test.
Sodium bicarbonate test:
Acids react with NaHCO3 toproduce brisk effervescence due to the evolution of CO2 gas.
Benzoic acid being an acid responds to this test, butethylbenzoate does not.
(v) Pentan-2-oneand pentan-3-one can be distinguished by iodoform test.
Iodoform test:
Pentan-2-one is a methyl ketone. Thus, it responds to thistest. But pentan-3-one not being a methyl ketone does not respond to this test.
(vi) Benzaldehydeand acetophenone can be distinguished by the following tests.
(a) Tollen’sTest
Aldehydes respond to Tollen’s test.Benzaldehyde being an aldehyde reduces Tollen’s reagent to give a red-brownprecipitate of Cu2O, but acetophenone being a ketone does not.
(b) Iodoformtest
Acetophenone being a methyl ketone undergoes oxidation bysodium hypoiodite (NaOI) to give a yellow ppt. of iodoform. But benzaldehydedoes not respond to this test.
(vii) Ethanaland propanal can be distinguished by iodoform test.
Iodoform test
Aldehydes and ketones having at least one methyl grouplinked to the carbonyl carbon atom responds to the iodoform test. Ethanalhaving one methyl group linked to the carbonyl carbon atom responds to thistest. But propanal does not have a methyl group linked to the carbonyl carbonatom and thus, it does not respond to this state.
