286951
In Lassaigne's extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with \(\mathrm{Fe}^{3+}\) due to the formation of
(d) In case, nitrogen and sulphur both are present in organic compound, sodium thiocyanate is formed. It gives blood red colour and no Prussian blue since there are no free cyanide ions.
\(\begin{aligned}
\mathrm{Na}+\mathrm{C}+\mathrm{N}+\mathrm{S} \longrightarrow & \mathrm{NaSCN} \\
\mathrm{Fe}^{3+}+\mathrm{SCN} \longrightarrow \longrightarrow & {[\mathrm{Fe}(\mathrm{SCN})]^{2+} } \\
& \text { Blood red }
\end{aligned}\)
NOTES If sodium fusion is carried out with excess of sodium, the thiocyanate decomposes to yield cyanide and sulphide. These ions now give their usual tests.
\(\mathrm{NaSCN}+2 \mathrm{Na} \longrightarrow \mathrm{NaCH}+\mathrm{Na}_{2} \mathrm{~S}\)
NCERT| Page-362 / N-284 | 2023
PRACTICAL CHEMISTRY (NEET PYQS)
286952
Nitrogen detection in an organic compound is carried out by Lassaigne's test. The blue colour
formed corresponds to which of the following formulae?
(b) Hydrazine \(\left(\mathrm{NH}_{2} \mathrm{NH}_{2}\right)\) does not contain carbon and hence on fusion with Na metal, it cannot form NaCN ; so it does not show Lassaigne's test for nitrogen.
NOTES This test fails in case of diazo compounds, dinitro compounds and compounds containing nitrogen in the ring.
286951
In Lassaigne's extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with \(\mathrm{Fe}^{3+}\) due to the formation of
(d) In case, nitrogen and sulphur both are present in organic compound, sodium thiocyanate is formed. It gives blood red colour and no Prussian blue since there are no free cyanide ions.
\(\begin{aligned}
\mathrm{Na}+\mathrm{C}+\mathrm{N}+\mathrm{S} \longrightarrow & \mathrm{NaSCN} \\
\mathrm{Fe}^{3+}+\mathrm{SCN} \longrightarrow \longrightarrow & {[\mathrm{Fe}(\mathrm{SCN})]^{2+} } \\
& \text { Blood red }
\end{aligned}\)
NOTES If sodium fusion is carried out with excess of sodium, the thiocyanate decomposes to yield cyanide and sulphide. These ions now give their usual tests.
\(\mathrm{NaSCN}+2 \mathrm{Na} \longrightarrow \mathrm{NaCH}+\mathrm{Na}_{2} \mathrm{~S}\)
NCERT| Page-362 / N-284 | 2023
PRACTICAL CHEMISTRY (NEET PYQS)
286952
Nitrogen detection in an organic compound is carried out by Lassaigne's test. The blue colour
formed corresponds to which of the following formulae?
(b) Hydrazine \(\left(\mathrm{NH}_{2} \mathrm{NH}_{2}\right)\) does not contain carbon and hence on fusion with Na metal, it cannot form NaCN ; so it does not show Lassaigne's test for nitrogen.
NOTES This test fails in case of diazo compounds, dinitro compounds and compounds containing nitrogen in the ring.
286951
In Lassaigne's extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with \(\mathrm{Fe}^{3+}\) due to the formation of
(d) In case, nitrogen and sulphur both are present in organic compound, sodium thiocyanate is formed. It gives blood red colour and no Prussian blue since there are no free cyanide ions.
\(\begin{aligned}
\mathrm{Na}+\mathrm{C}+\mathrm{N}+\mathrm{S} \longrightarrow & \mathrm{NaSCN} \\
\mathrm{Fe}^{3+}+\mathrm{SCN} \longrightarrow \longrightarrow & {[\mathrm{Fe}(\mathrm{SCN})]^{2+} } \\
& \text { Blood red }
\end{aligned}\)
NOTES If sodium fusion is carried out with excess of sodium, the thiocyanate decomposes to yield cyanide and sulphide. These ions now give their usual tests.
\(\mathrm{NaSCN}+2 \mathrm{Na} \longrightarrow \mathrm{NaCH}+\mathrm{Na}_{2} \mathrm{~S}\)
NCERT| Page-362 / N-284 | 2023
PRACTICAL CHEMISTRY (NEET PYQS)
286952
Nitrogen detection in an organic compound is carried out by Lassaigne's test. The blue colour
formed corresponds to which of the following formulae?
(b) Hydrazine \(\left(\mathrm{NH}_{2} \mathrm{NH}_{2}\right)\) does not contain carbon and hence on fusion with Na metal, it cannot form NaCN ; so it does not show Lassaigne's test for nitrogen.
NOTES This test fails in case of diazo compounds, dinitro compounds and compounds containing nitrogen in the ring.
286951
In Lassaigne's extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with \(\mathrm{Fe}^{3+}\) due to the formation of
(d) In case, nitrogen and sulphur both are present in organic compound, sodium thiocyanate is formed. It gives blood red colour and no Prussian blue since there are no free cyanide ions.
\(\begin{aligned}
\mathrm{Na}+\mathrm{C}+\mathrm{N}+\mathrm{S} \longrightarrow & \mathrm{NaSCN} \\
\mathrm{Fe}^{3+}+\mathrm{SCN} \longrightarrow \longrightarrow & {[\mathrm{Fe}(\mathrm{SCN})]^{2+} } \\
& \text { Blood red }
\end{aligned}\)
NOTES If sodium fusion is carried out with excess of sodium, the thiocyanate decomposes to yield cyanide and sulphide. These ions now give their usual tests.
\(\mathrm{NaSCN}+2 \mathrm{Na} \longrightarrow \mathrm{NaCH}+\mathrm{Na}_{2} \mathrm{~S}\)
NCERT| Page-362 / N-284 | 2023
PRACTICAL CHEMISTRY (NEET PYQS)
286952
Nitrogen detection in an organic compound is carried out by Lassaigne's test. The blue colour
formed corresponds to which of the following formulae?
(b) Hydrazine \(\left(\mathrm{NH}_{2} \mathrm{NH}_{2}\right)\) does not contain carbon and hence on fusion with Na metal, it cannot form NaCN ; so it does not show Lassaigne's test for nitrogen.
NOTES This test fails in case of diazo compounds, dinitro compounds and compounds containing nitrogen in the ring.
286951
In Lassaigne's extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with \(\mathrm{Fe}^{3+}\) due to the formation of
(d) In case, nitrogen and sulphur both are present in organic compound, sodium thiocyanate is formed. It gives blood red colour and no Prussian blue since there are no free cyanide ions.
\(\begin{aligned}
\mathrm{Na}+\mathrm{C}+\mathrm{N}+\mathrm{S} \longrightarrow & \mathrm{NaSCN} \\
\mathrm{Fe}^{3+}+\mathrm{SCN} \longrightarrow \longrightarrow & {[\mathrm{Fe}(\mathrm{SCN})]^{2+} } \\
& \text { Blood red }
\end{aligned}\)
NOTES If sodium fusion is carried out with excess of sodium, the thiocyanate decomposes to yield cyanide and sulphide. These ions now give their usual tests.
\(\mathrm{NaSCN}+2 \mathrm{Na} \longrightarrow \mathrm{NaCH}+\mathrm{Na}_{2} \mathrm{~S}\)
NCERT| Page-362 / N-284 | 2023
PRACTICAL CHEMISTRY (NEET PYQS)
286952
Nitrogen detection in an organic compound is carried out by Lassaigne's test. The blue colour
formed corresponds to which of the following formulae?
(b) Hydrazine \(\left(\mathrm{NH}_{2} \mathrm{NH}_{2}\right)\) does not contain carbon and hence on fusion with Na metal, it cannot form NaCN ; so it does not show Lassaigne's test for nitrogen.
NOTES This test fails in case of diazo compounds, dinitro compounds and compounds containing nitrogen in the ring.
