Abstract Why acetaldehyde solution reacting with Cu(OH)2 needed a strong alkaline solution in teaching? This paper calculated and compared equilibrium constants of the oxidation-reduction reaction of acetaldehyde in CuSO4 solution and strong alkaline Cu(OH)2 turbid liquid, and analyzed the reason combined with empirical study and kinetics mechanism of acetaldehyde oxidized by Cu(OH)2, then this study proposed a new view that the alkaline environment could significantly improve the reducibility of acetaldehyde and accelerate the reaction rate, the concentration of OH- or Cu(OH)42- in solution was the controlling factor of reaction.
