CBSE Class 12 Chemistry 2022 Term 2 Delhi Set 3

Question : 9 of 12

Marks: +1, -0

(a) What happens when
(i) Propanone is is treated with

{\CH}_3 {\MgBr}

and then hydrolysed?
(ii) Ethanal is treated with excess ethanol and acid?
(iii) Methanal undergoes Cannizzaro reaction?
(b) Write the main product in the following reaction?
(i)

2 {\CH}_3 {\COCl}+ ( {\CH}_3) _2 {\Cd} {──── ▸}

(ii)

{\CH}_3 {\CH}_2 {\CHO} { {──────── ▸}}↖{ {\Zn}( {\Hg}) \/ \;\text " Conc HCl "\;}

Solution:

(a) (i) When propanone reacts with ethyl magnesium bromide (Grignard's reagent) and hydrolysed, it forms aldehyde.

( {\CH}_3) _2 {\CO}+ {\H}_3 {\CCH}_2 {\MgBr} \;{  {──── ▸}}↙{ {\H}_2 {\O}}

{\CH_2\CH_3}↙{|}↙{ ( {\CH}_3) _2 {\COH}+ {\Mg}( {\OH}) {\Br}}

(ii) When ethanal reacts with excess ethanol and acid gives acetal.

(iii) Methanal will undergo Cannizzaro reaction as it possesses

\α

-hydrogen to form methanol.

OR
(b) (i)

{2 {\CH}_3 {\COCl}}↙{\Propanone}+{ ( {\CH}_3) _2 {\Cd} }↙{\Cadmium \Chloride}→2 {\CH}_3 {\COCH}_3

+ {\CdCl}_2

(ii)

{\CH}_3 {\CH}_2 {\CHO}   {──── ▸}↖{ {\Zn}- {\Hg}} ↙{\;\text " Conc. "\; {\HCl}} {{\CH}_3 {\CH}_2 {\CH}_3 }↙{\Propane}

(iii)

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