Amines MCQs for NEET — Chemistry Questions with Answers

The molecular formula C₄H₁₁N represents a primary amine with four carbon atoms. The general formula for primary amines is RNH₂, where R is an alkyl group. There are four possible primary amines with four carbon atoms: CH₃CH₂CH₂CH₂NH₂ (butylamine), CH₃CH₂CH(NH₂)CH₃ (isobutylamine), CH₃CH(NH₂)CH₂CH₃ (sec-butylamine), and (CH₃)₂CHCH₂NH₂ (tert-butylamine).

(b) -CN and -NC are different functional groups.

(b) ${\mathrm{CH}}_3\mathrm{COOH}\stackrel{{\mathrm{NH}}_3}{\to }{\mathrm{CH}}_3{\mathrm{COONH}}_4\stackrel{∆}{\to }{\mathrm{CH}}_3{\mathrm{CONH}}_2\stackrel{{\mathrm{P}}_2{\mathrm{O}}_5}{\to }{\mathrm{CH}}_3\mathrm{CN}\stackrel{\mathrm{Na}+{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}}{\to }{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{NH}}_2$

 As the number of alkyl groups increases, the electron density on nitrogen atom also increases, so the basic character increases but $3°$ amines are less basic than $2°$ amines due to steric hindrance of $3°$ amines, so the correct order of basicity is 

               Ammonia<$1°<3°<2°$

${\mathrm{NH}}_3<{\mathrm{C}}_2{\mathrm{H}}_5{\mathrm{NH}}_2<({\mathrm{C}}_2{\mathrm{H}}_5{)}_3\mathrm{N}<({\mathrm{C}}_2{\mathrm{H}}_5{)}_2\mathrm{NH}$

(c) ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{NH}}_2 \underset{0°\mathrm{c}}{\overset{{\mathrm{NaNO}}_2+\mathrm{HCl}}{\to }}{\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{N}}_2\mathrm{Cl}$

 Order of basic nature in a aqueous solution on the basis of K_b.

$({\mathrm{CH}}_3{)}_2\mathrm{NH}>{\mathrm{CH}}_3{\mathrm{NH}}_2>({\mathrm{CH}}_3{)}_3\mathrm{N}>{\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{NH}}_2$

(a) ${\mathrm{CH}}_3-\mathrm{N}\equiv \mathrm{C} +\hspace{0.17em}4\mathrm{H} \stackrel{{\mathrm{LiAlH}}_4}{\to }{\mathrm{CH}}_3{\mathrm{NHCH}}_3$

                                         Dimethylamine

On catalytic reduction or with lithium aluminium hydride (LiAlH₄) or with nascent hydrogen, alkyl isocyanide yield $2°$ amine whereas cyanide gives $1°$ amine on reduction.

When an organometallic compound (RMgX) reacts with cyanogen chloride (ClCN), the Grignard reagent undergoes nucleophilic addition followed by elimination, leading to the formation of an organo-nitrile (RCN). Hence, the correct option is RCN.

 $$\begin{gathered} {\mathrm{CH}}_3\mathrm{C}\equiv \mathrm{N}\underset{{\mathrm{LiAlH}}_4}{\overset{\mathrm{Reduction}}{\to }}{\mathrm{CH}}_3-{\mathrm{CH}}_2-{\mathrm{NH}}_2\stackrel{{\mathrm{HNO}}_3}{\to }{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH} \\ \mathrm{B} \mathrm{is} 1° \mathrm{amine} \mathrm{i}.\mathrm{e}. \mathrm{Ethanamine} \\ \therefore \mathrm{A} \mathrm{is} {\mathrm{CH}}_3\mathrm{CN} \end{gathered}$$