在乙腈中覆盖吡啶和DBU之间范围的自洽分光光度碱度标度。
Self-consistent spectrophotometric basicity scale in acetonitrile covering the range between pyridine and DBU.
作者信息
Kaljurand I, Rodima T, Leito I, Koppel IA, Schwesinger R
机构信息
Institute of Chemical Physics, Department of Chemistry, University of Tartu, Jakobi 2, 51014 Tartu, Estonia, and Chemisches Laboratorium, Institut fur Organische Chemie und Biochemie, Universitat Freiburg, Albertstrasse 21, D-791.
出版信息
J Org Chem. 2000 Sep 22;65(19):6202-8. doi: 10.1021/jo005521j.
A self-consistent spectrophotometric basicity scale in acetonitrile, including DBU, ten (arylimino)tris(1-pyrrolidinyl)phosphoranes, two (arylimino)tris(dimethylamino)phosphoranes, 2-phenyl-1,1,3, 3-tetramethylguanidine, 1-(2-tolyl)biguanide, benzylamine, two substituted benzimidazoles, pyridine, and ten substituted pyridines, has been created. The span of the scale is almost 12 pK(a) units. Altogether, 29 different bases were studied and 53 independent equilibrium constant measurements were carried out, each describing the relative basicity of two bases. The scale is anchored to the pK(a) value of pyridine of 12.33 that has been measured by Coetzee et al. Comparison of the basicity data of phenyliminophosphoranes and phenyltetramethylguanidines implies that the P=N bond in the (arylimino)tris(1-pyrrolidinyl)phosphoranes involves contribution from the ylidic (zwitterionic) structure analogous to that found in phosphorus ylides.
已建立了一个在乙腈中的自洽分光光度碱度标度，其中包括1,8-二氮杂二环十一碳-7-烯（DBU）、十种（芳基亚氨基）三（1-吡咯烷基）磷烷、两种（芳基亚氨基）三（二甲氨基）磷烷、2-苯基-1,1,3,3-四甲基胍、1-（2-甲苯基）双胍、苄胺、两种取代苯并咪唑、吡啶以及十种取代吡啶。该标度的范围几乎为12个pK(a)单位。总共研究了29种不同的碱，并进行了53次独立的平衡常数测量，每次测量都描述了两种碱的相对碱度。该标度以科茨等人测定的吡啶pK(a)值12.33为基准。苯基亚氨基磷烷和苯基四甲基胍的碱度数据比较表明，（芳基亚氨基）三（1-吡咯烷基）磷烷中的P=N键涉及类似于磷叶立德中发现的叶立德（两性离子）结构的贡献。
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