Determine the type of each of the arrows marked in the following arrow-pushing mechanism.




Type I: nucleophilic attack by a lone pair of electrons
Type II: heterolytic cleavage of a σbondType III: nucleophilic attack by the π electrons
Type IV: dissociation of a π bondType V: formation of a π bond

• A. Arrow (a) = type V
  Arrow (b) = type II
  Arrow (c) = type IV
  Arrow (d) = type I
• B. Arrow (a) = type IV
  Arrow (b) = type I
  Arrow (c) = type V
  Arrow (d) = type II
• C. Arrow (a) = type II
  Arrow (b) = type II
  Arrow (c) = type I
  Arrow (d) = type III
• D. Arrow (a) = type IV
  Arrow (b) = type III
  Arrow (c) = type IV
  Arrow (d) = type II

Answer: (B)