Question

drawn below is the structure of plavix® (clopidogrel), a medication used to manage blood clots. assign the absolute configuration of the chirality center as r - or s-. a. r- b. s- c. r- and s- are both possible d. the chiral center is neither r- nor s-

Explanation:

Step1: Determine priority of groups

According to Cahn - Ingold - Prelog (CIP) rules, higher atomic number atoms get higher priority. The groups attached to the chiral center are: 1) -COOCH₃ (oxygen has higher atomic number than other atoms in other groups), 2) -C₆H₄Cl (due to chlorine), 3) -N - containing ring, 4) H (lowest priority).

Step2: Orient the molecule

Place the lowest - priority group (H) away from the viewer.

Step3: Determine the configuration

The direction from the highest - to second - to third - priority group is clockwise. A clockwise direction corresponds to an R - configuration.

Answer:

A. R-