Question

Positive Beilstein test for halogen shows that

• A. none of these
• B. a halogen may be present
• C. a halogen is definitely present
• D. a halogen is absent

Answer 1

The correct option is B a halogen may be present

$\text{Beilstein test}$

Beilstein test is a type of flame test used to detect the presence of halogens in organic compounds. In this test the copper oxide on the wire reacts with the organic halide to produce a copper-halide compound that gives a blue-green colour to the flame.

$2CuO+4R-X\stackrel{heat}{\to }2Cu{X}_2$

$Cu{X}_2\stackrel{heat}{\to }Bluegreenlight$

The Beilstein test does not confirm the presence of halogen. Halogen containing impurities may give misleading results. Some other organic compounds like urea, thiourea, amide etc., also give the positive Beilstein test.

The reason being the fact that these halogen free compounds form cuprous cyanide which is volatile and decomposes to copper which burns with green flame.

So, this test just shows that halogen may be present.

Hence, the correct answer is option (B).