CBSE 2026 · Region 4 · Set 1 · Q28 · 3 marks
Answer the following :(a)Which isomer of $\displaystyle \mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$ is most reactive towards $\displaystyle \mathrm{S}_{\mathrm{N}} 1$ reaction ?(b)Predict the alkene that would be formed by dehydrohalogenation of $\displaystyle 1$-Bromo-$\displaystyle 1$-methylcyclohexane.(c)Although chlorine shows strong - I effect, yet it is ortho- and para-directing in electrophilic aromatic substitution reactions. Why ?
Answer the following :
(a)
Which isomer of $\displaystyle \mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$ is most reactive towards $\displaystyle \mathrm{S}_{\mathrm{N}} 1$ reaction ?
(b)
Predict the alkene that would be formed by dehydrohalogenation of $\displaystyle 1$-Bromo-$\displaystyle 1$-methylcyclohexane.
(c)
Although chlorine shows strong - I effect, yet it is ortho- and para-directing in electrophilic aromatic substitution reactions. Why ?
Marking-scheme solution
(a)
Tert-butyl bromide /(CH3)3CBr / $\displaystyle 2$-Bromo-$\displaystyle 2$-methylpropane
(b)
Or
(c) Because +R effect stabilizes the intermediate carbocation .
Haloalkanes and HaloarenesChemical Reactions of Haloalkanes and HaloarenesAnalyseshort_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.