Denegri Bernard, Streiter André, Jurić Sandra, Ofial Armin R, Kronja Olga, Mayr Herbert
Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovacića 1, 10000 Zagreb, Croatia.
Chemistry. 2006 Feb 8;12(6):1648-56. doi: 10.1002/chem.200500845.
A series of 21 benzhydrylium ions (diarylmethylium ions) are proposed as reference electrofuges for the development of a general nucleofugality scale, where nucleofugality refers to a combination of leaving group and solvent. A total of 167 solvolysis rate constants of benzhydrylium tosylates, bromides, chlorides, trifluoroacetates, 3,5-dinitrobenzoates, and 4-nitrobenzoates, two-thirds of which have been determined during this work, were subjected to a least-squares fit according to the correlation equation log k(25 degrees C) = sf(Nf + Ef), where sf and Nf are nucleofuge-specific parameters and Ef is an electrofuge-specific parameter. Although nucleofuges and electrofuges characterized in this way cover more than 12 orders of magnitude, a single set of the parameters, namely sf, Nf, and Ef, is sufficient to calculate the solvolysis rate constants at 25 degrees C with an accuracy of +/-16 %. Because sf approximately 1 for all nucleofuges, that is, leaving group/solvent combinations, studied so far, qualitative discussions of nucleofugality can be based on Nf.
提出了一系列21种二苯甲基离子（二芳基甲基离子）作为参考离去基团，用于建立通用的亲核离去能力标度，其中亲核离去能力是指离去基团和溶剂的综合作用。总共测定了167个二苯甲基对甲苯磺酸酯、溴化物、氯化物、三氟乙酸酯、3,5 -二硝基苯甲酸酯和4 -硝基苯甲酸酯的溶剂解速率常数，其中三分之二是在本研究中测定的，并根据相关方程log k(25℃) = sf(Nf + Ef)进行最小二乘法拟合，其中sf和Nf是亲核离去基团特异性参数，Ef是离去基团特异性参数。尽管以这种方式表征的亲核离去基团和离去基团涵盖了超过12个数量级，但一组参数，即sf、Nf和Ef，就足以计算25℃下的溶剂解速率常数，其准确度为±16%。由于到目前为止所研究的所有亲核离去基团，即离去基团/溶剂组合，sf约为1，因此亲核离去能力的定性讨论可以基于Nf。
