Huang Sijia, Kim Kangmin, Musgrave Grant M, Sharp Marcus, Sinha Jasmine, Stansbury Jeffrey W, Musgrave Charles B, Bowman Christopher N
Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309-0596, United States.
Department of Chemistry, University of Colorado Boulder, 596 UCB, Boulder, CO 80309-0596, United States.
Polym Chem. 2021 Jul 7;12(25):3619-3628. doi: 10.1039/d1py00363a. Epub 2021 May 29.
A combined experimental and computational study of the reactivities of seven commonly used Michael acceptors paired with two thiols within the framework of photobase-catalyzed thiol-Michael reactions is reported. The rate coefficients of the propagation (k), reverse propagation (k), chain-transfer (k), and overall reaction (k) were experimentally determined and compared with the well-accepted electrophilicity parameters of Mayr and Parr, and DFT-calculated energetics. Both Mayr's and Parr's electrophilicity parameters predict the reactivities of these structurally varying vinyl functional groups well, covering a range of overall reaction rate coefficients from 0.5 to 6.2 s. To gain insight into the individual steps, the relative energies have been calculated using DFT for each of the stationary points along this step-growth reaction between ethanethiol and the seven alkenes. The free energies of the individual steps reveal the underlying factors that control the reaction barriers for propagation and chain transfer. Both the propagation and chain transfer steps are under kinetic control. These results serve as a useful guide for Michael acceptor selection to design and predict thiol-Michael-based materials with appropriate kinetic and material properties.
本文报道了一项结合实验与计算的研究，该研究针对光碱催化硫醇-迈克尔反应框架内七种常用迈克尔受体与两种硫醇的反应活性展开。实验测定了链增长（k）、逆向链增长（k）、链转移（k）以及总反应（k）的速率系数，并将其与广泛认可的迈尔（Mayr）和帕尔（Parr）亲电参数以及密度泛函理论（DFT）计算的能量学进行了比较。迈尔亲电参数和帕尔亲电参数均能很好地预测这些结构各异的乙烯基官能团的反应活性，总反应速率系数范围为0.5至6.2 s。为深入了解各个步骤，利用DFT计算了乙硫醇与七种烯烃之间逐步增长反应中各驻点的相对能量。各个步骤的自由能揭示了控制链增长和链转移反应势垒的潜在因素。链增长和链转移步骤均受动力学控制。这些结果为迈克尔受体的选择提供了有用指导，有助于设计和预测具有适当动力学和材料性能的基于硫醇-迈克尔反应的材料。
