Onyido Ikenna, Obumselu Onyeka F, Egwuatu Chinyelu I, Okoye Nkechi H
Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.
Front Chem. 2023 Apr 27;11:1176746. doi: 10.3389/fchem.2023.1176746. eCollection 2023.
Organophosphorus esters fulfil many industrial, agricultural, and household roles. Nature has deployed phosphates and their related anhydrides as energy carriers and reservoirs, as constituents of genetic materials in the form of DNA and RNA, and as intermediates in key biochemical conversions. The transfer of the phosphoryl (PO) group is thus a ubiquitous biological process that is involved in a variety of transformations at the cellular level such as bioenergy and signals transductions. Significant attention has been paid in the last seven decades to understanding the mechanisms of uncatalyzed (solution) chemistry of the phospho group transfer because of the notion that enzymes convert the dissociative transition state structures in the uncatalyzed reactions into associative ones in the biological processes. In this regard, it has also been proposed that the rate enhancements enacted by enzymes result from the desolvation of the ground state in the hydrophobic active site environments, although theoretical calculations seem to disagree with this position. As a result, some attention has been paid to the study of the effects of solvent change, from water to less polar solvents, in uncatalyzed phospho transfer reactions. Such changes have consequences on the stabilities of the ground and the transition states of reactions which affect reactivities and, sometimes, the mechanisms of reactions. This review seeks to collate and evaluate what is known about solvent effects in this domain, especially their effects on rates of reactions of different classes of organophosphorus esters. The outcome of this exercise shows that a systematized study of solvent effects needs to be undertaken to fully understand the physical organic chemistry of the transfer of phosphates and related molecules from aqueous to substantially hydrophobic environments, since significant knowledge gaps exist.
有机磷酸酯在工业、农业和家庭领域发挥着多种作用。自然界将磷酸盐及其相关酸酐用作能量载体和储存库，作为DNA和RNA形式的遗传物质的组成部分，以及关键生化转化过程中的中间体。因此，磷酰基（PO）的转移是一个普遍存在的生物过程，涉及细胞水平上的各种转化，如生物能量和信号转导。在过去的七十年里，人们对磷酰基转移的非催化（溶液）化学反应机制给予了极大关注，因为有一种观点认为，酶在生物过程中将非催化反应中的解离过渡态结构转化为缔合态结构。在这方面，也有人提出，酶所带来的速率增强是由于疏水性活性位点环境中基态的去溶剂化作用，尽管理论计算似乎与这一观点不一致。因此，在非催化磷酰基转移反应中，人们对溶剂从水变为极性较小的溶剂所产生的影响进行了一些研究。这种变化会影响反应的基态和过渡态的稳定性，进而影响反应活性，有时还会影响反应机制。这篇综述旨在整理和评估该领域中关于溶剂效应的已知信息，特别是它们对不同类别的有机磷酸酯反应速率的影响。这项研究的结果表明，由于存在重大的知识空白，需要对溶剂效应进行系统研究，以全面理解磷酸盐及相关分子从水性环境转移到基本上疏水性环境的物理有机化学。
