Question

1) In the lab of synthesis of aspirin, how will adding HCl instead of phosphoric acid affect the outcome of the experiment.

2) In the lab of synthesis of aspirin, what is the purpose of using KMnO4 solution?

3) Suggest 2 other ways(besides use of hickman still) that you can use to influence the direction of reaction equilibrium in the lab dehydration of alcohol to alkenes

4) How will the absence of hickman still affect the outcome of the experiment dehydration of alcohol to alkenes

Answer 1

The Synthesis of aspirin involves the reaction between acetic anhydride and o-hydroxy benzoic acid in presence of strong acid such as phosphoric acid (scheme below). Phosphoric acid is used as a catalyst to activate the acetic anhydride group.

If we are to replace Phosphoric acid with HCl, the reaction will not proceed because conc HCl will be available only as 33 % in water which may react with acetic anhydride forming acetic acid.

The KMnO₄Test is used to detect the presence of phenols. Upon reaction completion of o-hydroxybenzoic acid to aspirin, the presence of free phenolic group is testing by adding KMnO4 solution. Disappearance of purple colour indicates the absence of phenolic group.