Question

An organic compound A with molecular formula C₅H₁₁Br when treated with alc.KOH forms B which with H₂O in H₂SO₄(dil) gives C.Compound C when treated with PBr₃ gives D which is an isomer of A.
D with Na in dry ether gives E, structure of which is different when A reacts with Na.
Identify A,B,C,D,E. Write suitable chemical reactions to show the conversion. Write the IUPAC name of each of the compounds.

Answer 1

​Dear Student,

$$\begin{gathered} \mathrm{Compound}\mathrm{A}\mathrm{is}{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br}\mathrm{i}.\mathrm{e}.1-\mathrm{bromopentane} \\ {\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br}+\mathrm{alc}.\mathrm{KOH}\to {\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{CH}={\mathrm{CH}}_2 \\ \mathrm{Therefore},\mathrm{B}\mathrm{is}\mathrm{Pent}-1-\mathrm{ene} \\ {\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{CH}={\mathrm{CH}}_2\underset{{\mathrm{H}}_2{\mathrm{SO}}_4}{\overset{{\mathrm{H}}_2\mathrm{O}}{\to }}{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{CH}\left(\mathrm{OH}\right){\mathrm{CH}}_3 \\ \mathrm{Therefore},\mathrm{C}\mathrm{is}\mathrm{Pentan}-2-\mathrm{ol} \\ {\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{CH}\left(\mathrm{OH}\right){\mathrm{CH}}_3\stackrel{{\mathrm{PBr}}_3}{\to }{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{CH}\left(\mathrm{Br}\right){\mathrm{CH}}_3 \\ \mathrm{D}\mathrm{is}2-\mathrm{bromopentane} \\ {\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{CH}\left(\mathrm{Br}\right){\mathrm{CH}}_3\underset{\mathrm{dry}\mathrm{ether}}{\overset{\mathrm{Na}}{\to }}{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{CH}\left({\mathrm{CH}}_3\right)\mathrm{CH}\left({\mathrm{CH}}_3\right){\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_3 \\ \mathrm{E}\mathrm{is}4,5-\mathrm{dimethyloctane} \\ \mathrm{When}\mathrm{A}\mathrm{reats}\mathrm{with}\mathrm{Na}: \\ {\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br}\underset{\mathrm{dry}\mathrm{ether}}{\overset{\mathrm{Na}}{\to }}{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_3 \\ \mathrm{Here}\mathrm{decane}\mathrm{is}\mathrm{formed}. \end{gathered}$$