The ph value is too high or too low to be synthesized. In alkaline environment, benzoin condensation reaction forms carboanion, which catalyzes nucleophilic addition reaction. If the ph value is low and the acidity is strong, VB 1 can't form C- ion, and it will change back to VB 1 after combining with H+, so the pH value of benzoin condensation reaction should be 9- 10. In the synthesis of benzoin, the addition of nucleophiles to benzaldehyde is the key. Under alkaline conditions, it is beneficial to the formation of nucleophiles and the deprotonation of protonated diphenyl ethanol ketone to generate benzoin.