The development and implementation of a research-based organic chemistry laboratory experiment is presented. The experiment was designed to simulate a scientific research environment, involve students in critical thinking, and develop the student's ability to analyze and present research-based data. In this experiment, a laboratory class synthesized a library of penicillins, where each student had the freedom to choose which penicillin he or she wanted to synthesize. After the different penicillins were synthesized, the products were tested for antimicrobial activity. All results from the class were compared and penicillins were grouped according to their ability to inhibit bacterial growth. Finally, students evaluated the structure-function relationship between the penicillin's structure and its antimicrobial activity. (Contains 1 figure and 1 scheme.)