Question

Consider a hypothetical scenario in which there is no piperidine in the lab to run this reaction; however you find some pyridine and pyridine derivatives in the lab (shown below); all of which are weak bases. Which base is the best substitute forpipidine? Which base is the worst substitute for piperidine? Briefly describe why the base that you chose was the best choice. Assume that all of the bases will completely dissolve in the reaction mixture. (3 Marks) pyridine 2-fluoropyridine 2-methylpyridine 3-bromopyridine pKb 8.77 pKb 13.56 pkb 8.00 Kb 11.16

Answer 1

p^k_b = 8.77 p^k_b = 13.56 p^k_b = 8.00 p^k_b = 11.16 p^k_a = 14 - p^k_b = 5.23 = 0.44 p^k_a = 6.00 = 2.84 Higher the p^k_a of conjugate acid, the stronger the base. The conjugate acid is the species that results after the base forms a bond to H. The p^k_a of pipe dine = 11 piper dine is strongest base so the best substitute of pipe dine is the because it have p^k_a = 6.00 and worst substitute as it have p^k_a = 0.44