Q29 / 180 · AIIMS 2015 · Chemistry

Lassaigne's test for the detection of nitrogen fails in

  • A
    $\mathrm{H}_2 \mathrm{~N}-\mathrm{CO}-\mathrm{NHNH}_2 \cdot \mathrm{HCl}$
  • Correct answer
    B
    $\mathrm{NH}_2-\mathrm{NH}_2 \cdot \mathrm{HCl}$
  • C
    $\mathrm{C}_6 \mathrm{H}_5-\mathrm{NH}-\mathrm{NH}_2 \cdot \mathrm{HCl}$
  • D
    $\mathrm{C}_6 \mathrm{H}_5 \mathrm{CONH}_2$

Solution

Lassaigne's test is given by those nitrogenous compounds in which carbon is also present along with nitrogen. In $\mathrm{NH}_2-\mathrm{NH}_2 \cdot \mathrm{HCl}$, carbon is absent, so it does not give Lassaigne's test.

Hence, the correct answer is option: 'B'.

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