How can we distinguish chemically the following pairs of compounds?
(i) `CH_(3)CHO` and `CH_(3)COCH_(3)`
(ii) `CH_(3)CHO` and `C_(6)H_(5)CHO`
(iii) `C_(6)H_(5)COCH_(3)` and `C_(6)CH_(5)COC_(6)H_(5)`
(iv) `CH_(3)CHO` and `CH_(3)CH_(2)CHO`

Explanation

(i) `CH_(3)CHO` gives +ve Tollens test and forms silver mirror with ammoniacal `AgNO_(3)`.
`CH_(3)CHO+[Ag(NH_(3))_(2)]^(+)toCH_(3)COO^(-)+Agdarr`
while `CH_(3)COCH_(3)` does not give this test. (ii) `CH_(3)CHO` forms silver mirror with Tollen.s reagent while does not give this test.
(iii) gives +ve lodoform reaction and forms a yellow ppt of `CHI_(3)` as it is a methyl ketone while does not give this reaction.
(iv) `CH_(3)CHO` shows iodoform reaction whereas `CH_(3)CH_(2)CHO` does not.