Aliphatic Compounds Containing Nitrogen - Result Question 8
####8. A compound ’ $X$ ’ on treatment with $Br _2 / NaOH$, provided $C _3 H _9 N$, which gives positive carbylamine test. Compound ’ $X$ ’ is
(2019 Main, 11 Jan II)
(a) $CH _3 COCH _2 NHCH _3$
(b) $CH _3 CH _2 CH _2 CONH _2$
(c) $CH _3 CON\left(CH _3\right) _2$
(d) $CH _3 CH _2 COCH _2 NH _2$
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Answer:
Correct Answer: 8. (b)
Solution:
- The molecular formula, $C _3 H _9 N$ refers to four structural isomers of amines
(a) $CH _3 CH _2 CH _2 NH _2$
(b) $CH _3-CH _{\mid}-CH _3$
(c)
$\underset{\text { Secondary amine }}{CH _3-NH-CH _2 CH _3}$
(d)
Here, only $a$ and $b$ (primary amines) can be prepared from their respective amides by Hoffmann bromamide $\left(Br _2 / NaOH\right)$ method and can give positive carbylamine test.
$\Rightarrow CH _3 CH _2 CH _2 \xrightarrow{|} NH _2 \xrightarrow[\substack{Na _2 CO _3}]{Br _2} CH _3 CH _2 CH _2-NH _2$
So, ’ $X$ ’ can be $CH _3 CH _2 CH _2-CONH _2$ (a) or $CH _3 CH\left(CONH _2\right) CH _3$ (b).
Carbylamine test given by (a) and (b)
$CH _3 CH _2 CH _2 NH _2+CHCl _3+3 KOH \xrightarrow{\Delta}$
As (b) is not among the given options So, it is ruled out and compound ( $X$ ) is $CH _3 CH _2 CH _2 CONH _2$.
