Official course description: For chemistry majors; recommended for premedical students and other science majors. CHEM 128A not open for credit to students with credit in CHEM 8. Prerequisites: CHEM 1B with a grade of C or better or permission of the insructor; for CHEM 128B: CHEM 128A with a grade of C or better. Introduction to structure and reactivity of principal classes of organic compounds with emphasis on theory and mechanism.