Synthesis of Aspirin

Question

A student carries out the experiment using 3.00g of salicylic acid and an excess of acetic anhydride. If this is the case, what is the limiting reactant? 2. The student from #1 collected 2.95g of aspirin at the end of the experiment. Calculate the theoretical yield of aspirin( from the data in #3) and the percent yield of the reaction. Show all calculations.

Answer 1

Since the acetic anhydride is present in excess, it cannot be the limiting reactant. Thus, the limiting reactant under these conditions is salicylic acid.

Theoretical yield will be based on how much aspirin can theoretically be produced from 3.00 g of salicylic acid. 3.00 g. The reaction is salicylic acid + acetic anhydride ==> aspirin + acetic acid. In terms of chemical formula it is C₇H₆O₃ + C₄H₆O₃ ==> C₉H₈O₄ + C₂H₄O₂

3.00 g SA x 1 mol/138 g x 1 mole aspirin/mole SA x 180 g/mol = 3.91 g aspirin (theoretical yield)

Percent yield = actual yield/theoretical yield (x100%) = 2.95 g/3.91 g (x100%) = 75.4%