Question

An organic compound having molecular mass `60` is found to contain `C = 20%, H = 6.67%`, and `N = 46.67%`, while rest is oxygen. On heating, it gives `NH_(3)` along with a solid residue. The solid residue gives violet color with alkaline copper sulphate solution. The compounds is
A. `(NH_(2))_(2)CO`
B. `CH_(3)CONH_(2)`
C. `CH_(3)NCO`
D. `CH_(3)CH_(2)CONH_(2)`

Answer 1

Correct Answer - A
Out of given organic compounds, only urea has molecular mass `= 60 u` and percentage of `% N = 46.67 %`. When gently heated, urea loses ammonia to form biuret:
`(NH_(2))_(2) CO hArr NH_(3) + HNO overset((NH_(2))_(2)CO)rarrH_(2)NCONHCONH_(2)`
or
`H_(2)NCO-NH_(2)+H-NHCONH_(2) overset(-NH_(3))rarr underset("Biuret")(H_(2)NCONHCONH_(2))`
When an aqueous biuret solution is treated with sodium hydroxide solution and a drop of copper sulphate solution, a violetcolor is produced. This is known as the biuret reaction which is characteristic of compounds containing the grouping `-CONH -`, e.g., proteins.