Fig. 8. The composition of the reaction mixture: (a) piperazine reacts with benzyl alcohol (the molar ratio of piperazine to benzyl alcohol in the reactant is 1 : 3); (b) aniline reacts with 1,5-pentanediol (the molar ratio of aniline to 1,5-pentanediol in the reactant is 1 : 2).