Explain why benzocaine precipitates during the neutralization.
With the addition of an acid, the amine group on the benzocaine will become protonated. The protonation creates a positive charge on the benzocaine molecule. Because of this, benzocaine will become soluble in a polar solvent. However, when the solution is returned to a more basic pH level, the amine will no longer be protonated. Thus, the benzocaine will no longer be soluble and will precipitate during neutralization.