CBSE 2026 · Region 3 · Set 2 · Q22 · 3 marks
Give reasons for the following :(a)Alkyl halides, though polar, yet their solubility in water is very low.(b)p-Dichlorobenzene has higher melting point than those of o- and m-isomers.(c)$\displaystyle \mathrm{CH}_{3}-\mathrm{I}$ is more reactive than $\displaystyle \mathrm{CH}_{3}-\mathrm{Br}$ towards $\displaystyle \mathrm{S}_{\mathrm{N}} 2$ reactions.
Give reasons for the following :
(a)
Alkyl halides, though polar, yet their solubility in water is very low.
(b)
p-Dichlorobenzene has higher melting point than those of o- and m-isomers.
(c)
$\displaystyle \mathrm{CH}_{3}-\mathrm{I}$ is more reactive than $\displaystyle \mathrm{CH}_{3}-\mathrm{Br}$ towards $\displaystyle \mathrm{S}_{\mathrm{N}} 2$ reactions.
Marking-scheme solution
(a)
Less energy is released when new attractions are set up between the
haloalkane and the water molecules as these are not as strong as the
original hydrogen bonds in water. / Because of the inability of alkyl
halide to form H-bond with water.
(b)
Because of symmetry, para isomer fits well into the crystal lattice.
(c)
Because I is a better leaving group due to its larger size than Br.
Haloalkanes and HaloarenesPhysical Properties of Haloalkanes and HaloarenesUnderstandshort_answermedium
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CBSE Class 12 Chemistry past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.