An analyst receives a sample that contains MDMA, a basic drug with a pKa of 9.9. The analyst dissolves the powder in a buffer solution with a pH of 12. After filtering, they pour the aqueous buffer solution into a separatory funnel. They add chloroform, close and shake. Two layers form. Where will the MDMA be?

Question

Quizplus · Accepted Answer

MDMA is a basic drug with a pKa of 9.9. In a solution with a pH higher than its pKa, it will have a greater tendency to be in its neutral form (unionized). In this case, the pH of the buffer solution is higher than its pKa. When the solution is added to the separatory funnel along with chloroform, MDMA will be present in both layers. However, since chloroform is a non-polar solvent and MDMA in its neutral form is also non-polar, the majority of the MDMA will partition to the chloroform layer. Therefore, the MDMA will be in the chloroform layer.

An Analyst Receives a Sample That Contains MDMA, a Basic