Distinction between pairs of compounds
Phenyl acetaldehyde `(C_(6)H_(5)CH_(2)CHO)` and acetophenone `(C_(6)H_(5)COCH_(3))`
(a) By the use of Tollens' reagent and Fehling solution.
Iodoform Test.

Explanation

Following tests help to distinguish these :
Phenyl acetaldehyde gives silver mirror with Tollens. reagent and red ppt. of `Cu_(2)O` with Fehling solution.
Acetophenone does not give the above tests.
(i) `C_(6)H_(5)CH_(2)CHO+underset("Tollen.s reagent")(2[Ag(NH_(3))_(2)]^(+))+3OH^(-)`
`rarrunderset("Silver mirror")(2Agdarr)+C_(6)H_(5)CH_(2)COO^(-)+4NH_(3)+2H_(2)O`
(ii) `C_(6)H_(5)CH_(2)CHOunderset("Fehling.s Solution")(+ 2Cu^(2+))+5OH^(-)`
`rarrC_(6)H_(5)CH_(2)COO^(-)+undersetunderset("red ppt.")("Cuprous oxide")(Cu_(2)Odarr+3H_(2)O)`
(b) Acetophenone is a methyl ketone, So, it gives iodoform test while phenylacetaldehyde does not,
`underset("Acetophenone")(C_(6)H_(5)COCH_(3))+3NaOIrarrunderset("Iodoform (yellow ppt.)")(CHI_(3)+C_(6)H_(5)COONa)+2NaOH`