Kraus Jakob, Kortus Jens
Institute of Theoretical Physics, TU Bergakademie Freiberg, Leipziger Str. 23, D-09599 Freiberg, Germany.
ACS Omega. 2023 Mar 31;8(14):12693-12701. doi: 10.1021/acsomega.2c07756. eCollection 2023 Apr 11.
The thermodynamics and kinetics of the pyrolysis of (+)-catechin, a building block of the condensed tannins found in recipes for sustainable binders, are evaluated at the DLPNO-CCSD(T) level and compared to other methods from quantum chemistry. Using the climbing image nudged elastic band method coupled with transition state optimization, minimum energy paths and highest-energy transition states are identified for the first two pyrolysis steps, a catechol split-off with subsequent dehydrogenation. While the catechol split-off path was very smooth, the dehydrogenation featured an additional transition state in the form of an OH group rotation. The combined reaction was judged endothermic in the range of 0 to 1250 K and exergonic at 1000 K and above. It is shown that the catechol split-off is the rate-determining step of the pyrolysis of catechin, which is equivalent to kinetic inhibition at all investigated temperatures.
在DLPNO - CCSD(T)水平下评估了(+)-儿茶素（一种可持续粘合剂配方中缩合单宁的组成部分）热解的热力学和动力学，并与量子化学的其他方法进行了比较。使用爬山图像推挤弹性带方法结合过渡态优化，确定了前两个热解步骤（儿茶酚脱除并随后脱氢）的最小能量路径和最高能量过渡态。虽然儿茶酚脱除路径非常平滑，但脱氢过程以OH基团旋转的形式呈现出一个额外的过渡态。该复合反应在0至1250 K范围内被判定为吸热反应，在1000 K及以上为放能反应。结果表明，儿茶酚脱除是儿茶素热解的速率决定步骤，这相当于在所有研究温度下的动力学抑制。
