Question

Name the functional group based upon the result of each test. A positive Silver Nitrate indicates the presence of an ___________. A positive Ceric Nitrate test indicates the presence of an ___________ . A positive Bromination test indicates the presence of an ___________ . A positive Tollens test indicates the presence of an ___________.

Answer 1

1)Silver nitrate test:-A positive silver nitrate test indicates the presence of halide ions like Fluorine, chlorine, bromine & iodine.

Fluorine - No precipitate

Chlorine- white precipitate

Bromine- very pale creamy precipitate

Iodine - very pale yellow precipitate.

2) ceric nitrate test:- A positive ceric nitrate test indicates the presence of functional group alcohol(-OH).

A red or red brown colour indicates the positive test.

[Ce(NO3)6]2- + R-OH -------> [R-O-Ce(NO3)5]2-. + HNO3

3) Bromination test:-A positive Bromination test indicates the presence of unsaturation (carbon carbon double bond & carbon carbon triple bond), anilines and phenols.

4) Tollen's test:- A positive Tollen's test indicates the presence of Aldehydes.But this test is also positive for alpha hydroxy ketone and formic acid.

But this test is also positive for alpha hydroxy ketone, because two tautomerization take place, ketone has en-ol form and then one more tautomerization take place with hydroxyl group(--H group). All the three forms in equilibrium give Tollen's test.

This test is also positive for Formic acid(HCOOH), because carboxyl group(-C=O) behave as Aldehydes group & hence give positive Tollen's test.