Kinetics and Mechanism of the Benzenethiolysis of 2,4-Dinitrophenyl and 2,4,6-Trinitrophenyl Methyl Carbonates and <i>S</i>-(2,4-Dinitrophenyl) and <i>S</i>-(2,4,6-Trinitrophenyl) Ethyl Thiolcarbonates
作者:Enrique A. Castro、Paulina Pavez、José G. Santos
DOI:10.1021/jo034082w
日期:2003.5.1
respectively, consistent with concerted mechanisms. TNPC is more reactive toward benzenethiolate anions than DNPC, and TNPTC more than DNPTC due to the better leaving groups involved. Comparison of the kinetic results obtained in this work with those for the concerted phenolysis of the same substrates shows that benzenethiolate anions are better nucleophiles toward carbonates than isobasic phenoxide anions
碳酸2,4-二硝基苯基和2,4,6-三硝基苯基甲基碳酸酯(分别为DNPC和TNPC)与S-(2,4-二硝基苯基)和S-(2,4,6-三硝基苯基)硫代碳酸乙酯的反应( DNPTC和TNPTC)分别与一系列苯硫醇盐阴离子在水中进行动力学研究,温度为25.0摄氏度,离子强度为0.2 M(KCl)。这些反应在过量的苯硫醇盐下服从拟一级反应动力学,在后一种反应物中是一级反应。但是,在4-硝基苯硫代酸根阴离子与TNPC和TNPTC的反应中使用了可比的反应物浓度,显示了二级动力学。亲核速率常数与pH无关,但TNPC与4-甲氧基和五氟苯硫醇酯的反应除外。TNPTC与苯硫醇盐,4-氯-和3-氯苯硫醇盐,表现出对酸的依赖性。对于DNPC,TNPC,DNPTC和TNPTC的反应,亲核速率常数的布朗斯台德图呈线性,斜率分别为β= 0.9、1.0、0.9和0.9。在DNPC和DNPTC在pK(a)处的反应中,在布朗斯台德图中没有发现断裂。4