# Acid in Imine Formation

Why is a strong acid like $\ce{H2SO4}$ used for imine formation here instead of a weaker acid like TsOH? I thought that if the pH was too low, the amine molecule would get protonated to an ammonium, which are not nucleophilic?

• In short, this reaction has two steps: 1. Nucleophilic attack of nitrogen on the carbonyl carbon 2. elimination of water in acidic conditions – Gaurang Tandon Feb 11 '18 at 11:21

The p$K_a$ of $\ce{H2SO4}$ is $-9$ while that of TosOH is $-6.5$, but both will form $\ce{EtNH3^+}$ which has a p$K_a$ between 10 and 11.