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.