4-nitrophenol is formed during the synthesis of paracetamol. It is used in various xenobiotic metabolism processes and other essential biochemical processes. It is metabolized via cytochrome P450 enzyme. The present work reported the hydroxylations of 4-nitrophenol at the ortho position by Cytochrome P450 metalloenzyme. Truncated model of putative active oxidant i.e. ferryl oxo porphyrin cation radical [Fe^IV(O)(heme^+•)], referred as Cpd I in cytochrome P450 enzymes has been used to mimic the behavior of enzyme. In the current investigations, 4-nitrophenol (Substrate) is modeled with Cpd I and reaction mechanism for two degenerate spin states named as doublet (LS) and quartet (HS) is performed to dwell the overall potential energy landscape, along with electronic structures and properties of reactant complex (RC), transition states (TS), intermediates (IM) and product complex (PC). The reaction is stepwise with electrophillic addition as the rate determining step, spin selectivity product formation is observed only at high spin (HS) surface. So, the present reaction pathway is single state reactivity (SSR) by forming the suicidal complex at low spin state (LS).

4-硝基苯酚是在合成扑热息痛过程中形成的。它用于各种异生物质代谢过程和其他重要的生化过程。它通过细胞色素 P450 酶代谢。目前的工作报告了细胞色素 P450 金属酶在邻位 4-硝基苯酚的羟基化。推定活性氧化剂的截断模型，即 Ferrell 氧代卟啉阳离子自由基 [Fe ^IV (O)(heme ^+•)]，在细胞色素 P450 酶中称为 Cpd I，已被用于模拟酶的行为。在目前的研究中，4-硝基苯酚（底物）用 Cpd I 建模，并进行了两种简并自旋态的反应机制，称为双重态 (LS) 和四重态 (HS)，以驻留整体势能图，以及电子结构和反应物复合物 (RC)、过渡态 (TS)、中间体 (IM) 和产物复合物 (PC) 的性质。该反应是逐步进行的，亲电加成作为速率决定步骤，仅在高自旋 (HS) 表面观察到自旋选择性产物的形成。因此，目前的反应途径是通过在低自旋态 (LS) 形成自杀复合物的单态反应性 (SSR)。