The results showed that HCl functionated to protect amino-group by reacting with NDA to form NDA hydrochlorate, which restrained NDA from reacting with NDI to form urea resulting in the improvement of NDI selectivity.

• 结果表明, 由于HCl与 NDA生成了快反应产物 NDA盐酸盐, 抑制了 NDA与 NDI生成脲副反应的进行, 起到了保护氨基的作用, 从而提高了 NDI 的选择性。