Test Index

NCERT Class XII Chemistry
Chapter - Haloalkanes and Haloarenes
Questions with Solutions

© examsnet.com
Question : 22 of 31
Marks: +1, -0
What happens when
(i) n-butyl chloride is treated with alcoholic KOH,
(ii) bromobenzene is treated with Mg in the presence of dry ether,
(iii) chlorobenzene is subjected to hydrolysis,
(iv) ethyl chloride is treated with aqueous KOH,
(v) methyl bromideis treated with sodium in the presence of dry ether,
(vi) methyl chloride is treated with KCN?
Solution:  
(i)CH3CH2CH2CH2Cln-Butylchloride→alc. KOHCH3CH2CH=CH2But-1-ene(i) \underset{\text{n-Butylchloride}}{\mathrm{CH_3CH_2CH_2CH_2Cl}}\xrightarrow[\text{alc. KOH}]{}\underset{\text{But-1-ene}}{\mathrm{CH_3CH_2CH=CH_2}}
The reaction is an example of β-hydrogen elimination brought about by C2H5O⊖C_2H_5O^{\ominus}
Chlorobenzene is highly unreactive towards nucleophilic substitution.
However, it can be hydrolysed to phenol by heating in aqueous sodium hydroxide solution at a temperature of 623 K and 300 atm pressure. The presence of an electron withdrawing group increases the reactivity of haloarenes.
(iv)CH3−CH2Cl→KOH/H2OCH3−CH2−OHSN2 reaction(iv) \mathrm{CH_3 -CH_2 Cl}\xrightarrow[\mathrm{KOH}/\mathrm{H_2O}]{}\underset{\mathrm{S_N2}\ \text{reaction}}{\mathrm{CH_3-CH_2-OH}}
(v)2CH3−Br+2Na→dry etherCH3−CH3+2NaBrWurtz reaction(v) 2\mathrm{CH_3 -Br} + 2\mathrm{Na}\xrightarrow[\text{dry ether}]{}\underset{\text{Wurtz reaction}}{\mathrm{CH_3-CH_3+2NaBr}}
(vi)CH2ClMethylchloride→EtOH/H2OKCNCH3−CNEthanenitrile(vi) \underset{\text{Methylchloride}}{\mathrm{CH_2Cl}}\xrightarrow[\mathrm{EtOH}/\mathrm{H_2O}]{\mathrm{KCN}}\underset{\text{Ethanenitrile}}{\mathrm{CH_3 -CN}}
© examsnet.com
Go to Question:
Prev Question
Next Question