Reaction conditions: 70 °C, the molar ratio of TMAC to NDA was 0.05:1.
As the feeding amount of ECH increases, the reactions of the initial, middle and late stages were conducted under the conditions of excessive neodecanoic acid (NDA). The results indicate that DCP noticeably exists in the reaction system, even only a little amount of ECH (with molar ratio of 10%) was added. With the amount of ECH increasing from 10% to 100%, the DCP concentration only increases by 2.1%, however, the value of \(\eta_{\text{ECH}}\) greatly rises from 50% to 90%. A reasonable interpretation of these results is that the side reaction causing the formation of DCP precedes the main reaction of ECH with NDA. There have been some studies16, 17, 23 about the mechanism of the acidolysis reaction of ECH with organic acid catalyzed by quaternary ammonium salts (shown in Scheme 3 ). The formation of quaternary ammonium carboxylate with the aid of TMAC is presumed to be the first step (R.3 and R.4), and the generated carboxylate would be the functional substance to catalyze the acidolysis reaction (R.5). The results listed in Table 2 completely comply with this catalytic mechanism. The relatively low values of \(\eta_{\text{Acid}}\) and\(\eta_{\text{ECH}}\) in the early stage can be explained by the formation of tetramethylammonium neodecanoate (TMAN), which involves the interaction of TMAC, ECH and NDA. And the subsequent increase of\(\eta_{\text{Acid}}\) and \(\eta_{\text{ECH}}\) is due to the ongoing main reaction of ECH with NDA catalyzed be TMAN.