Academic journal article Journal of College Science Teaching

The Chemistry of Cocaine

Academic journal article Journal of College Science Teaching

The Chemistry of Cocaine

Article excerpt

Engaging undergraduate organic chemistry students is often very challenging. It requires special effort to generate enthusiasm for learning such seemingly abstract concepts as functional group chemistry, synthetic routes, and reaction mechanisms. Students often do not see the relevance of these concepts to their own lives or interests. Classroom materials are needed that can be used to connect concepts in organic chemistry to applications that students can relate to. Drug abuse, which is a growing problem, is a topic that many students can connect to emotionally. This case study focuses on the chemistry of cocaine to teach a number of core concepts in organic chemistry, specifically nucleophilic addition reactions, nucleophilic acyl substitution, and cocaine metabolism. It also requires that students read and analyze an original research paper on efforts to develop a treatment for cocaine addiction. Use of the case has the added benefit of raising awareness of cocaine abuse.

The case was designed for the second course in a two-course sequence in undergraduate organic chemistry, as carbonyl group chemistry is normally covered in this course. However, the case could be adapted and used in medicinal chemistry classes.

Objectives

The case teaches these concepts:

* chemistry of aldehydes and ketones: nucleophilic addition reactions (NAR),

* chemistry of carboxylic acids and derivatives: nucleophilic acyl substitution (NAS),

* application of NAR and NAS in multistep synthesis of biologically active compounds,

* metabolism of cocaine, and

* comparison of physical properties of an amine and its salt.

Classroom management

Students are expected to prepare in advance for the case, completing the tasks described next. The in-class portion takes one hour to complete. Students also complete several post-case study homework assignments. I have taught this case in classes with 18 to 25 students. For much larger classes, the help of one or more teaching assistants is recommended.

Pre-case study preparation

At the beginning of the semester, students are informed that the case is available online (http://sciencecases. lib.buffalo.edu/cs/collection) and that they will be undertaking the case on a specific date later in the semester. Students are expected to complete the following before the day of the case:

* Read the case study. As part of this, students are told that along with reading the case they should attempt to answer the case questions because they will be required to share their responses with group members during the in-class case study session.

* Locate and read the research article referenced in the case (Zheng et al. 2008). I tell students to read it to understand the key ideas and not worry about all the details in the article.

* Complete the pre-case study questions (see the case). Students are expected do this assignment individually and submit it two weeks prior to the case class date; the assignment is graded and returned to them a week before the case is run in class. This pre-case study assignment requires students to study and write the major mechanisms underlying the reactions in the case study. Students are provided with access to relevant reading resources to help them answer the questions on enzyme function and kinetics (Manoharan and Dreisbach 1988; Voet and Voet 2004).

In-Class Activities

The case is presented in a one-hour class period, and students are allowed to consult their organic chemistry textbook and other materials of their choice. The students are assigned to work in groups of four or five to answer the case study questions. They are asked to select a team member to moderate the discussions. Groups are chosen such that each group has members with a range of subject matter competence. The latter is determined on the basis of the cumulative scores students have earned on exams, labs, quizzes, and homework assignments in the course so far. …

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