JAMB - Chemistry (2019 - No. 6)
Hydrocarbons which will react with Tollen's reagent conform to the general formula
C\(_n\)H\(_{2n}\)
C\(_n\)H\(_{2n + 2}\)
C\(_n\)H\(_{2n - 2}\)
C\(_n\)H\(_{2n + 1}\)OH
Explicació
Only hydrocarbons containing an aldehyde group (RCHO) or a terminal alkyne (R-C≡C-H) will react with Tollens' reagent, leading to a silver mirror formation or a white precipitate, respectively. Aldehydes are oxidized by Tollens' reagent (ammoniacal silver nitrate solution) to form carboxylic acids, while the silver ions (Ag+) are reduced to metallic silver (Ag), which deposits as a silver mirror on the walls of the test tube.
Terminal alkynes react with Tollens' reagent, producing a white precipitate of silver acetylide.