CBSE 2025 · Region 4 · Set 1 · Q22 · 3 marks
Account for the following :(i)Allyl chloride is hydrolysed more readily than n-propyl chloride.(ii)Isocyanides are formed when alkyl halides are treated with silver cyanide.(iii)Methyl chloride reacts faster with $\displaystyle \overline{\mathrm{O}} \mathrm{H}$ ion in $\displaystyle \mathrm{S}_{\mathrm{N}} 2$ reaction than t-butyl chloride.Complete the following reactions by writing the structural formulae of 'A' and 'B' :(i)$\displaystyle \mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2} \xrightarrow[\text { Peroxide }]{\mathrm{HBr}}$ 'A' $\displaystyle \xrightarrow{\text { aq. } \mathrm{KOH}}$ 'B'(ii)$\displaystyle \underset{\mathrm{Cl}}{\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHCH}_{3}} \xrightarrow[\Delta]{\text { alc. } \mathrm{KOH}}$ 'A' $\displaystyle \xrightarrow{\mathrm{HBr}}$ 'B'(iii)' A ' $\displaystyle \xrightarrow{\mathrm{Mg}} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{MgCl} \xrightarrow[\mathrm{H}^{+}]{\mathrm{H}_{2} \mathrm{O}}$ (Main product)
Account for the following :
(i)
Allyl chloride is hydrolysed more readily than n-propyl chloride.
(ii)
Isocyanides are formed when alkyl halides are treated with silver cyanide.
(iii)
Methyl chloride reacts faster with $\displaystyle \overline{\mathrm{O}} \mathrm{H}$ ion in $\displaystyle \mathrm{S}_{\mathrm{N}} 2$ reaction than t-butyl chloride.
Complete the following reactions by writing the structural formulae of 'A' and 'B' :
(i)
$\displaystyle \mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2} \xrightarrow[\text { Peroxide }]{\mathrm{HBr}}$ 'A' $\displaystyle \xrightarrow{\text { aq. } \mathrm{KOH}}$ 'B'
(ii)
$\displaystyle \underset{\mathrm{Cl}}{\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHCH}_{3}} \xrightarrow[\Delta]{\text { alc. } \mathrm{KOH}}$ 'A' $\displaystyle \xrightarrow{\mathrm{HBr}}$ 'B'
(iii)
' A ' $\displaystyle \xrightarrow{\mathrm{Mg}} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{MgCl} \xrightarrow[\mathrm{H}^{+}]{\mathrm{H}_{2} \mathrm{O}}$ (Main product)
Marking-scheme solution
(i)
Greater stability of allylic carbocation due to resonance.
(ii)
Being covalent in nature, only nitrogen is free to donate electron pair in AgCN.
(iii)
Less sterically hindered carbon in Methyl chloride/ greater steric hinderance on tertiary
carbon of t-butyl chloride.
$\displaystyle 22$(b)
(i)
A =CH3CH2CH2Br B = CH3CH2CH2OH
(ii)
A = CH3CH=CHCH3 B= CH3CH2CH(Br)CH3
(iii)
A = CH3CH2Cl B= CH3CH3
Haloalkanes and HaloarenesChemical Reactions of Haloalkanes and HaloarenesUnderstandshort_answerhard
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CBSE Class 12 Chemistry past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.