Which one of the following reactions does NOT belong to "Lassaigne's test"?
- Na + X NaX
- 2CuO + C 2Cu + CO2
- Na + C + N NaCN
- 2Na + S Na2S
Answer
(2) 2CuO + C 2Cu + CO2
Solution
In Lassaigne's test the organic compound is fused with sodium metal; N, S and halogens are converted into ionic sodium salts:
Na + C + N NaCN
2Na + S Na2S
Na + X NaX (X = Cl, Br, I)
As per NCERT, heating the compound with copper(II) oxide, 2CuO + C 2Cu + CO2, is the test for carbon (and hydrogen), not a part of Lassaigne's test.
Answer: (2)