DPPH (= 2,2-Diphenyl-1-picrylhydrazyl) Radical-Scavenging Reaction of Protocatechuic Acid (= 3,4-Dihydroxybenzoic Acid): Difference in Reactivity between Acids and Their Esters
作者:Shizuka Saito、Jun Kawabata
DOI:10.1002/hlca.200690139
日期:2006.7
Protocatechuic acid (= 3,4-dihydroxybenzoic acid; 1) exhibits a significantly slow DPPH (= 2,2-diphenyl-1-picrylhydrazyl) radical-scavenging reaction compared to its esters in alcoholic solvents. The present study is aimed at the elucidation of the difference between the radical-scavenging mechanisms of protocatechuic acid and its esters in alcohol. Both protocatechuic acid (1) and its methyl ester
与其在醇类溶剂中的酯相比,原儿茶酸(= 3,4-二羟基苯甲酸;1)显示出显着缓慢的DPPH(= 2,2-二苯基-1-吡啶基肼基)自由基清除反应。本研究旨在阐明原儿茶酸及其酯在醇中的自由基清除机理之间的差异。原儿茶酸(1)及其甲酯2均迅速清除了2当量。自由基分别被转化为相应的邻醌结构1a和2a(方案)。然后,儿茶酚的再生(=苯-1,2-二醇)的结构发生经由将甲醇分子亲核加成到邻醌上,分别得到醇加合物1f和2c,它们可以清除另外的2当量。激进的。但是,原儿茶酸(1)的反应超出了邻醌的形成要比其甲酯2的反应慢得多。结果表明,与1的酯相比,1的自由基清除反应更慢是由于吸电子的羧酸官能团与给电子的羧酸根离子的离解,从而降低了邻苯二甲酸酯的亲电子性。-醌,导致酒精分子对亲核攻击的敏感性降低。