(S)-(−)-1-Phenylethanaminium 4-(2,4,6-triisopropylbenzoyl)benzoate (S-PEATPBB) undergoes a photochemical reaction in its crystalline form upon UV irradiation and forms three different products: the first product is the result of a Yang cyclization with the participation of the δ-H atom of o-isopropyl (product D) and the second and third products are obtained via a Norrish–Yang reaction with the involvement of the γ-H atom of 2-isopropyl (product P) and 6-isopropyl (product Z). These products are formed in different proportions (D > P >> Z). The path and kinetics of the reaction were monitored step-by-step using crystallographic methods, both under ambient and high-pressure conditions. The reactivity of S-PEATPBB depends strongly on the geometry of the reaction centre and the volume of the reaction cavity. Due to the geometrical preferences making the cyclization reaction easier to proceed, product D dominates over the other products, while the formation of product Z becomes difficult or almost impossible at high pressure. The reaction proceeds with an increase of the unit-cell volume, which, suppressed by high pressure, results in a significant decrease of the reaction rate. The crystal lattice of S-PEATPBB shows high elasticity. The quality of the partially reacted crystal remains the same after decompression from 0.75 GPa to 0.1 MPa.

中文翻译：

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多组分产物形成的结构原因及高压的影响

( S )-(-)-1-Phenylethanaminium 4-(2,4,6-triisopropylbenzoyl)benzoate (S-PEATPBB) 在紫外线照射下以其结晶形式发生光化学反应并形成三种不同的产物：第一种产物是o-异丙基的 δ-H 原子参与的杨环化的结果（产物 D），第二和第三产物是通过以下方式获得的2-异丙基（产物 P）和 6-异丙基（产物 Z）的 γ-H 原子参与的 Norrish-Yang 反应。这些产品以不同的比例形成（D > P >> Z）。在环境和高压条件下，使用晶体学方法逐步监测反应的路径和动力学。S-PEATPBB 的反应性很大程度上取决于反应中心的几何形状和反应腔的体积。由于几何偏好使环化反应更容易进行，产物 D 优于其他产物，而产物 Z 的形成在高压下变得困难或几乎不可能。反应随着晶胞体积的增加而进行，这在高压的抑制下导致反应速率显着降低。S-PEATPBB 的晶格显示出高弹性。从 0.75 GPa 减压到 0.1 MPa 后，部分反应的晶体的质量保持不变。