Question

Had you performed the silver nitrate test for alkyl halides on your isolated product (1-bromobutane). Would the formation of a precipitate at room temperature indicate your product was a primary, secondary, or tertiary halide?

Answer 1

The silver nitrate test is used to detect the presence of halide group with fair bit of accuracy.

It is quite a sensitive test.

Tertirary halides almost instantly produce the precipitate whereas primary halides take longer because tertiary carbocations are most stable and primary the least.

In the case of 1-bromobutane, the reactions taking place are following:

CH₃CH₂CH₂CH₂Br + H₂O CH₃CH₂CH₂CH₂OH + H⁺ + Br^-

Br^- + AgNO₃ AgBr + NO₃^-

The precipitate formed is of AgBr. It takes fair bit of time to form becasue the original halide is primary and thus we can tell that our halide was primary because of the long time taken for reaction completion as tertiary halides instantly form precipitate whereas secondary halides take a few minutes.