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Q.
$ CH_3CHO$ and $C_6H_5CH_2CHO$ can be distinguished chemically by :
Solution:
$CH_3CHO$ and $C_6H_5CH_2CHO$ are aliphatic aldehydes and hence react with Tollen's reagent, Febling- solution and Benedict solution. These reagents cannot be used to distinguish them $CH_3CHO$ reacts with $NaOH$ and $I_2$ to form yellow crystalline iodoform while $C_6H_5CH_2CHO$ does not react with it.
$\ce{CH_3CHO + 3I_2 + 4NaOH ->$\underset{\mathrm{Yellow \, crystalline \, ppt}}{\ce{CHI_3} }$ + 3Nal + 3H_2O}$
$C_6H_5CH_2CHO + 3I_2 + 4NaOH \rightarrow No $reaction
$\therefore $ Iodoform test can be used to distinguish between $CH_3CHO$ and $C_6H_5CH_2CHO$