When C6H5CHO condenses with (CH3CO)2O in presence of sodium acetate then cinnamic acid is formed. This reaction is called Perkin reaction BenzaldehydeC6H5—CHO+Acetic anhydnde(CH3CO)2OCH3COONa100∘C Cinnamic acidC6H5CH=CHCOOH+Acetic acidCH3COOH