The autoxidation of organic materials is a detrimental radical chain process often leading to their rapid deterioration unless they are protected by preventive and/or chain breaking antioxidants. The properties of the more important family of the latter ones, that one of phenols, are illustrated in this tutorial review. A short outline of diarylamine antioxidants is also given. We describe simple experimental methods employed for the determination of the two parameters more useful for estimating the inhibiting power of antioxidants, that is the kinetic rate constant for their reaction with the chain carrying peroxyl radicals, k(inh), to give persistent phenoxyl or aminyl radicals and the bond dissociation enthalpy BDE(X-H) (X = O, N) of the bond cleaved in the inhibition process. The dependence of these parameters on the number and nature of the substituents is discussed and, in the case of phenols, a simple rule allowing to predict with reasonable accuracy the BDE and k(inh) values, from their structure. The effect of solvent polarity on the antioxidant power is also described. Finally, the information on the mechanism of reaction between phenols and peroxyl radicals provided by both experiments and theoretical calculations are examined. Because of difficulties associated with the analysis of non-homogenous systems all the reported results refer to homogenous solution in which experimental data can be analysed by means of more reliable and complete treatments.

中文翻译：

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自由基中间体在抑制自氧化反应中。

有机材料的自氧化是有害的自由基链过程，通常会导致其快速降解，除非它们受到预防和/或断链抗氧化剂的保护。本教程复习中说明了较重要的一种酚（一种酚）的特性。还给出了二芳基胺抗氧化剂的简短概述。我们描述了用于确定两个参数的简单实验方法，这两个参数对于估算抗氧化剂的抑制能力更为有用，这是抗氧化剂与带有过氧自由基基团k（inh）的反应的动力学速率常数，从而得到持久的苯氧基或氨基自由基和在抑制过程中裂解的键的离解焓BDE（XH）（X = O，N）。讨论了这些参数对取代基数量和性质的依赖性，对于酚类，则给出了一个简单的规则，可以根据其结构准确预测BDE和k（inh）值。还描述了溶剂极性对抗氧化剂能力的影响。最后，考察了实验和理论计算所提供的有关酚与过氧自由基之间反应机理的信息。由于与非均质系统分析相关的困难，所有报告的结果均指均质溶液，在该溶液中可以通过更可靠，更完整的方法来分析实验数据。还描述了溶剂极性对抗氧化剂能力的影响。最后，考察了实验和理论计算所提供的有关酚与过氧自由基之间反应机理的信息。由于与非均质系统分析相关的困难，所有报告的结果均指均质溶液，在该溶液中可以通过更可靠，更完整的方法来分析实验数据。还描述了溶剂极性对抗氧化剂能力的影响。最后，考察了实验和理论计算所提供的有关酚与过氧自由基之间反应机理的信息。由于与非均质系统分析相关的困难，所有报告的结果均指均质溶液，在该溶液中可以通过更可靠，更完整的方法来分析实验数据。