Aldehyde and Ketone MCQ Questions & Answers in Organic Chemistry | Chemistry

Fehling solution, Schiff’s reagent & Tollen’s reagent react only with aldehydes but Grignard reagents react both with aldehydes and ketones.

\[HC \equiv CH\xrightarrow[{20\% \,{H_2}S{O_4}}]{{1\% \,HgS{O_4}}}\mathop {C{H_3}CHO}\limits_{\left[ A \right]} \]       \[\xrightarrow[{{H_2}O}]{{C{H_3}MgX}}\mathop {C{H_3}CHOHC{H_3}}\limits_{\left[ B \right]} \xrightarrow{{\left[ O \right]}}\]       \[\mathop {C{H_3}COC{H_3}}\limits_{{\text{Acetone}}\left[ C \right]} \]

Aldehydes with no $$\alpha {\text{ - }}H$$  atom undergo Cannizzaro reaction on heating with conc. alkali solution. Hence, only $${C_6}{H_5}CHO$$    will undergo the reaction.

2 - hydroxy propane or secondary alcohol is oxidised into propanone ( corresponding because in 2 - hydroxy propane, secondary alcoholic group is present and it is oxidised into ketone ).

Only acetaldehyde and methyl ketones give iodoform test.

Only those aldehyde undergoes aldol condensation which have $$\alpha $$ - hydrogen, so $$C{H_3}C{H_2}CHO$$    give this reaction because it contains $$\alpha $$ - hydrogen atom. Aldol condensation proceed in presence of strong base. Aldol condensation are divided into two parts one is self aldol condensation and another is cross-aldol condensation. When both molecules are same called as self aldol and vice versa.

\[CH \equiv CH\xrightarrow[{HgS{O_4}}]{{30\% \,{H_2}S{O_4}}}\]     \[\mathop {C{H_3}CHO}\limits_{\left[ A \right]} \xrightarrow{{NaOH}}\]     \[\mathop {C{H_3}CHOHC{H_2}CHO}\limits_{\left[ B \right]} \]