29Si NMR spectra of trimethylsilyl (TMS) and tert-butyldimethylsilyl (TBDMS) derivatives of selected diols were measured under standardized conditions (i.e., in diluted CDCl3 solutions). Application of the recently reported correlation between the chemical shifts in TMS and TBDMS derivatives revealed considerable and systematic deviations which exceeded experimental errors and error estimates from the correlation. Two possible explanations of the deviations are considered: interaction between the two bulky substituent groups and invalidity of the reported correlation for simple hydroxy derivatives. An independent study of analogous derivatives of monohydroxy compounds has shown that the linear correlation holds but the slope and intercept are significantly different from those reported previously on the basis of a study of amino acid derivatives. The data obtained for the diol derivatives fit the new correlation very well and no indication of an interaction between the bulky TBDMS groups was noticed. However, deviations do occur in branched diol derivatives in which branching reduces accessibility of the oxygen atoms surface to associate with proton donors. The largest deviation was found when intramolecular hydrogen bond was formed.
29Si核磁共振谱测定了选定二醇的三甲基硅基(TMS)和叔丁基二甲基硅基(TBDMS)衍生物在标准化条件下(即在稀释的CDCl3溶液中)。应用最近报道的TMS和TBDMS衍生物化学位移之间的相关性显示出明显和系统性的偏差,超过了实验误差和相关性误差估计。对偏差的两种可能解释是:两个笨重取代基之间的相互作用以及对简单羟基衍生物的报道相关性的无效性。对单羟基化合物的类似衍生物的独立研究表明,线性相关性成立,但斜率和截距与以前基于氨基酸衍生物研究所报告的值显著不同。对二醇衍生物获得的数据非常符合新的相关性,没有发现叔丁基TBDMS基团之间的相互作用的迹象。然而,在支链二醇衍生物中确实存在偏差,其中支链减少了氧原子表面与质子供体结合的可及性。当形成分子内氢键时,发现最大的偏差。