Experimental and theoretical approaches to the protonation of thiourea:: A convenient nucleophile in coordination chemistry revisited
Experimental and theoretical approaches to the protonation of thiourea:: A convenient nucleophile in coordination chemistry revisited
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DOI：
10.1002/zaac.200500157
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发表时间：
2005-01-01
影响因子：
1.4
通讯作者：
van Eldik, R
中科院分区：
文献类型：
--
作者：
Schiessl, WC;Summa, NK;van Eldik, R
利用电位法、紫外可见光谱、核磁共振光谱、质谱以及DFT计算等方法，对硫脲在水、非水介质中的质子化过程进行了研究。在水介质中，在pH 0 ~ 7范围内没有发现质子化的证据，这与文献中引用的约为- 1.2的典型pK(a)值（质子化硫脲的酸解离常数）一致。文献中引用的大部分质子化常数是不正确的，显然是指pK值。在甲醇和水-二氧六环混合物中，硫脲的质子化发生在高得多的pK值下，这一定与质子化物质在这些介质中的稳定性有关。
The protonation of thiourea was reinvestigated in aqueous and non-aqueous media using potentiometric, UV-vis, NMR, MS spectroscopy, as well as DFT calculations. In aqueous medium, no evidence for protonation could be found in the pH range 0 to 7, in agreement with typical pK(a) values (acid dissociation constants of protonated thiourea) quoted in the literature of around - 1.2. Most of the protonation constants quoted in the literature are incorrect and apparently refer to pK, values. Protonation of thiourea occurs at a much higher pK, value in methanol and in water-dioxane mixtures, which must be related to the stabilization of the protonated species in such media.