NEET Practice Questions (MCQs) with Answers & Solutions

Lindlar's catalyst (Pd-CaCO3 poisoned with Pb(OAc)2 and quinoline) is used for the semi-hydrogenation of alkynes to cis-alkenes. It adds hydrogen atoms in a cis fashion across the triple bond, selectively producing the cis-alkene product.

$$\begin{gathered} \left(\mathrm{c}\right)\mathrm{CH}\equiv \mathrm{CH}+\mathrm{Na}\to \mathrm{CH}\equiv \mathrm{CNa}\stackrel{\mathrm{RX}}{\to }\mathrm{CH}\equiv \mathrm{CR} \\ \mathrm{CH}\equiv \mathrm{CH}+\mathrm{RMgX}\to \mathrm{CH}\equiv \mathrm{CMgX}\stackrel{\mathrm{RX}}{\to }\mathrm{CH}\equiv \mathrm{CR} \end{gathered}$$

(d) Na/C₂H₅OH, LiAlH₄ or NaBH₄ are used for this purpose.

(b) CH₃CH=CH₂ $\stackrel{{\mathrm{B}}_2{\mathrm{H}}_6}{\to }$(CH₃CH₂CH₂)₃B 

                        $\stackrel{{\mathrm{H}}_2{\mathrm{O}}_2}{\to }$CH₃CH₂CH₂OH + H₃BO₃;

The process is called hydroboration.

(b) A characteristic reaction of aldehyde with Tollen's reagent. Rest all also attacks C=C.

Propene (CH3CH=CH2) reacts with diazomethane (CH2N2) in the presence of UV radiation via a carbene insertion reaction. The methylene carbene (:CH2) generated from diazomethane inserts into the C=C bond of propene, forming methyl cyclopropane.

$\left(\mathrm{d}\right)\mathrm{CH}\equiv \mathrm{CH}\underset{0°\mathrm{C}}{\overset{\mathrm{NaOCl}}{\to }}\mathrm{CCl}\equiv \mathrm{CCl}$

(c) ${\mathrm{CH}}_2={\mathrm{CH}}_2 + \mathrm{HBr} \stackrel{ }{\to } {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{Br} \stackrel{\mathrm{HOH}}{\to } {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} \underset{+ {\mathrm{I}}_2 \left(\mathrm{excess}\right)}{\overset{{\mathrm{Na}}_2{\mathrm{CO}}_3}{\to }} \mathrm{Iodoform}$

(B) It is how Zn-Cu couple is used.

$\left(\mathrm{d}\right) {\mathrm{CH}}_4+{\mathrm{HNO}}_3\stackrel{∆}{\to }{\mathrm{CH}}_3{\mathrm{NO}}_2; \mathrm{nitration} \mathrm{reaction}$