Aliphatic Compounds Containing Nitrogen - Result Question 35
####37. A basic volatile nitrogen compound gave a foul smelling gas when treated with chloroform and alcoholic KOH. A $0.295 g$ sample of the substance dissolved in aq. $HCl$ and treated with $NaNO _2$ solution at $0^{\circ} C$, liberated a colourless, odourless gas whose volume corresponds to $112 mL$ at STP.
After evolution of the gas was complete, the aqueous solution was distilled to give an organic liquid which did not contain nitrogen and which on warming with alkali and iodine gave a yellow precipitate. Identify the original substance assuming that it contains one $N$-atom per molecule.
$(1993,4 M)$
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Solution:
- Starting compound is a primary amine.
$R-NH _2+CHCl _3+KCl \longrightarrow \underset{\text { foul smell }}{R-NC}$
Also, $\quad R-NH _2+HNO _2 \longrightarrow R-OH+N _2$
Moles of $N _2=\frac{112}{22500}=5 \times 10^{-3}$
$\because \quad$ One mole of $N _2$ is obtained from 1.0 mole of $R-NH _2$, mole of $R-NH _2=5 \times 10^{-3}$
$\Rightarrow 5 \times 10^{-3} mol R-NH _2$ weigh $=0.295 g$
1 mole of $R-NH _2$ will weigh $=\frac{0.295}{5 \times 10^{-3}}=59 g$
In $R-NH _2,-NH _2$ has molar mass $=16$
$\Rightarrow R$ - has molar mass $=43$
Also, the alcohol $R-OH$ gives iodoform test; it must has the following skeleton :
$R^{\prime}-\underset{OH}{CH}-CH _3$
$\Rightarrow \quad R^{\prime}$ - has molar mass $=15\left(CH _3\right)$
$\Rightarrow$ Original compound is $CH _3-\stackrel{+}{C} CH-NH _2$
