Acyl/aroylperoxyl radicals:: a comparative study of the reactivity of peroxyl radicals resulting from the α-cleavage of ketones
Acyl/aroylperoxyl radicals:: a comparative study of the reactivity of peroxyl radicals resulting from the α-cleavage of ketones
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DOI：
10.1039/b109309f
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发表时间：
2002-01-01
影响因子：
3.3
通讯作者：
McGarvey, DJ
中科院分区：
文献类型：
--
作者：
El-Agamey, A;McGarvey, DJ
采用2,2′-氮化杂氮（3-乙基苯并噻唑-6-磺酸）二铵盐（ABTS 2）作为选择性自由基探针，采用纳秒激光灰光解（LFP）和竞争动力学方法研究了不同酮类在甲醇中a裂解产物中加入氧生成的酰基/芳基过氧自由基的反应。在使用的实验条件下，ABTS（2-）对酰基/芳基过氧基自由基（与烷基过氧基自由基相反）的选择性得到了ABTS（2-）对氧浓度依赖性的支持。-)在亚微秒时间尺度上进行脱碳的酰基自由基的自由基离子吸收振幅。ABTS对氧浓度的依赖性。-)瞬态吸收反映了脱碳和氧加成之间的竞争，因此该数据也提供了脱碳和氧加成速率的信息。支持ABTS（2-）对酰基/芳基过氧自由基选择性的进一步证据是，使用不同的酮前体对特定的酰基/芳基过氧自由基所获得的结果之间的一致性。过氧自由基对ABTS（2-）的反应顺序为：芳基过氧基>酰基过氧基>>烷基过氧基。利用ABTS（2-）作为酰基/芳基过氧基自由基的监测仪，利用竞争动力学获得了各种酰基/芳基过氧基自由基与维生素E和trolox反应的速率常数。
Employing 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt ( ABTS 2) as a selective radical probe, nanosecond laser ash photolysis (LFP) and competitive kinetic methods have been used to investigate the reactions of acyl/aroylperoxyl radicals derived from the addition of oxygen to the a cleavage products of various ketones in methanol. The selectivity of ABTS(2-) for acyl/aroylperoxyl radicals ( as opposed to alkylperoxyl radicals), under the experimental conditions used, is supported by the oxygen concentration dependence of the ABTS(.-) radical ion absorption amplitudes for acyl radicals that undergo decarbonylation on sub-microsecond timescales. The oxygen concentration dependence of the ABTS(.-) transient absorption reflects the competition between decarbonylation and oxygen addition and therefore this data also provides information on decarbonylation and oxygen addition rates. Further evidence in support of the selectivity of ABTS(2-) for acyl/aroylperoxyl radicals is the agreement between results obtained from using different ketone precursors for specific acyl/aroylperoxyl radicals. The order of reactivity of the peroxyl radicals towards ABTS(2-) is found to be aroylperoxyl > acylperoxyl >> alkylperoxyl. The use of ABTS(2-) as a monitor for acyl/aroylperoxyl radicals has been exploited by using competitive kinetics to obtain rate constants for the reactions of various acyl/aroylperoxyl radicals with vitamin E and trolox.