In Lassaigne’s test, the presence of nitrogen in an organic compound is detected by converting it into sodium cyanide (\text{NaCN}). This is done by fusing the organic compound with sodium in a fusion tube. When water is added, the following reaction occurs:
To confirm the presence of nitrogen, the resulting solution is treated with ferrous sulfate (\text{FeSO}_4) and then heated. During this step, ferrous cyanide (\text{Fe(CN)}_2) is formed:
The compound \text{Fe}_4[\text{Fe(CN)}_6]_3 is responsible for the characteristic Prussian blue color. This confirms the presence of nitrogen in the organic compound.
Let's analyze why \text{Fe}_4[\text{Fe(CN)}_6]_3 is the correct answer:
\text{Na}_4[\text{Fe(CN)}_6] is not the Prussian blue complex but a precursor (sodium ferrocyanide).
\text{Fe}_2[\text{Fe(CN)}_6] is not a standard compound related to the traditional Lassaigne's test for nitrogen.
\text{Fe}_3[\text{Fe(CN)}_6]_4 is not the Prussian blue complex and does not form under these conditions.
Thus, the compound responsible for the Prussian blue color in Lassaigne's test is \text{Fe}_4[\text{Fe(CN)}_6]_3.
Organic Chemistry – Some Basic Principles and Techniques - Reaction Mechanism
SN1 Reaction Mechanism:
SN1 reaction mechanism takes place by following three steps –
Formation of carbocation
Attack of nucleophile
Deprotonation
SN2 Reaction Mechanism:
The SN2 reaction mechanism involves the nucleophilic substitution reaction of the leaving group (which generally consists of halide groups or other electron-withdrawing groups) with a nucleophile in a given organic compound.
