Laboratoire de Chimie Agro-Industrielle, Université de Toulouse, INRAE, Toulouse, France.
Lipids. 2020 Jul;55(4):329-339. doi: 10.1002/lipd.12239. Epub 2020 Apr 22.
The synthesis of undecylenic acid partial esters can be performed at mild temperature with a classical esterification reaction catalyzed by dodecylbenzene sulfonic acid (DBSA). A semi-empirical molecular modeling on the different reaction intermediates indicates that DBSA can strongly decrease their heats of formation through hydrogen bonding. Diester formation seems to be thermodynamically favored with a selectivity for alpha, alpha, or alpha, beta forms that depend on the geometry of the catalyst-intermediate configuration. Triesters are not favored but a high selectivity for monoesters requires a kinetic control. Experimental approach, considering different DBSA concentrations and temperature partially confirms the theoretical predictions but surfactant properties of DBSA and monoesters may induce nonpredicted geometries. Global apparent activation energies are calculated, corresponding to the formation and hydrolysis of mono and diesters. If water trapping allows the decrease of hydrolysis reaction constants, the presence of water and subsequent phase separation may explain differences between theoretical and experimental results and could help increasing monoester selectivity.
十一烯酸部分酯的合成可以在温和的温度下进行，通过十二烷基苯磺酸（DBSA）催化的经典酯化反应来完成。对不同反应中间体的半经验分子建模表明，DBSA 可以通过氢键强烈降低它们的生成热。二酯的形成似乎在热力学上是有利的，其对 α、α、或 α、β 形式的选择性取决于催化剂-中间体构型的几何形状。三酯不受青睐，但单酯的高选择性需要动力学控制。考虑不同 DBSA 浓度和温度的实验方法部分证实了理论预测，但 DBSA 和单酯的表面活性剂性质可能会导致非预测的几何形状。计算了形成和水解单酯和二酯的总表观活化能。如果水捕获可以降低水解反应常数，那么水的存在和随后的相分离可能会解释理论和实验结果之间的差异，并有助于提高单酯的选择性。
