Question

Give two examples of pseudo-unimolecular reactions.

Answer 1

These are reactions involving two reactants, but one is taken in large excess, so the reaction appears to be first order with respect to the limiting reactant.

Acid-catalysed hydrolysis of ethyl acetate:

\[\ce{CH3COOC2H5 + H2O −>[H+] CH3COOH + C2H5OH}\]

(Water is in large excess; rate depends only on [CH₃COOC₂H₅]).

Hydrolysis of sucrose (inversion of cane sugar):

\[\ce{C12H22O11 + H2O −>[H+] C6H12O6 + C6H12O6}\]

(Water is in large excess; rate depends only on [sucrose]).