Lecture 6: More HSAB & Arrow-Pushing Announcements: Problem Set 3 posted online. Due Thurs, 9/21/17 • Today: Hard-Soft Acid-Base Theory (HSAB) - continued • More arrow-pushing • Basic conditions ◦ Substitution at electrophilic π-bonds ‣ Acidic Conditions ◦ Stability, formation, and reactions of carbocations ‣