Zawadiak Jan, Mrzyczek Marek
Faculty of Chemistry, Silesian University of Technology, Krzywoustego 4, 44-100, Gliwice, Poland.
Magn Reson Chem. 2013 Nov;51(11):689-94. doi: 10.1002/mrc.4001. Epub 2013 Aug 23.
Influence of dibenzoylmethane's substituents in meta and para positions on chemical shift values of tautomers' characteristic protons was investigated in four solvents with (1)H NMR spectroscopy: acetone-d(6), benzene-d(6), CDCl(3) and deuterated dimethyl sulfoxide (DMSO-d(6)). It was proved that the influence of substituents on chemical shifts strongly depends on the kind of the solvent; the greatest changes were observed in benzene-d6 and the smallest in CDCl(3). In acetone-d(6) and DMSO-d(6), the influence of substituents on chemical shifts is similar and the most regular. It allowed a fair correlation of chemical shifts of para-substituted dibenzoylmethane derivatives' characteristic protons with Hammett substituent constants in these solvents. In CDCl(3), characteristic protons' chemical shifts were near (1)H NMR spectroscopy measurement error limits, and, therefore, correlation with Hammett substituent constants in this solvent was unsatisfactory. In benzene, although the changes of chemical shifts are the most evident, the changes are also the most irregular, and, therefore, correlation in this solvent failed completely. Results of meta-substituted derivatives were much more irregular, and their correlation with Hammett substituent constants was poor in all investigated solvents.
采用核磁共振氢谱（¹H NMR）技术，在四种溶剂（氘代丙酮-d(6)、氘代苯-d(6)、氯仿-d(3)和氘代二甲亚砜（DMSO-d(6)））中，研究了间位和对位二苯甲酰甲烷取代基对互变异构体特征质子化学位移值的影响。结果表明，取代基对化学位移的影响强烈依赖于溶剂种类；在氘代苯-d6中观察到的变化最大，而在氯仿-d(3)中最小。在氘代丙酮-d(6)和DMSO-d(6)中，取代基对化学位移的影响相似且最为规律。这使得在这些溶剂中，对位取代二苯甲酰甲烷衍生物特征质子的化学位移与哈米特取代基常数之间存在较好的相关性。在氯仿-d(3)中，特征质子的化学位移接近¹H NMR光谱测量误差极限，因此，与该溶剂中的哈米特取代基常数的相关性并不理想。在苯中，虽然化学位移的变化最为明显，但变化也最不规则，因此，在该溶剂中的相关性完全失败。间位取代衍生物的结果更为不规则，在所有研究的溶剂中，它们与哈米特取代基常数的相关性都很差。
