2.2 Preparation of DESs
ChCl was chosen as the HBA, and phenol (Pho), p-toluenesulfonic acid (TsOH), benzoic acid (BOA) and hydroxylamine hydrochloride (NH2OH•HCl) were selected as HBD, respectively. The synthesis of DESs was carried out in a glass flask. The acceptor and donor of the hydrogen bond were mixed according to molar ratio of 1/2, 1/1, 1/2, 1/2 to prepare ChCl-Pho (1:2), ChCl-TsOH (1:1), ChCl-BOA (1:2), and ChCl-NH2OH•HCl (1:2), respectively, with the structures shown in Figure 133-35. The mixtures were heated with stirring for 1 h after the appearance of homogeneous liquid phase in the oil bath.