In the compound shown below, abstraction of which hydrogen affords the most stable carbon radical? Hc He Hd Options: A: B: C: HC D: E: He (1 mark) In a Hammett plot, a concave upward deviation indicates: A B an increase in positive charge in the rate-determining step the reaction is faster for electron-donating substituents an increase in negative charge in the rate-determining step a change in the rate-determining step a change in mechanism D E Options: B (a) (b) (c) (d) D (e) E (1 mark)