shorter length of the CSe bond [1.824(5) Å vs. 1.840(3) Å]. The Gibbs free energy of activation of C-N bond rotation (ΔG≠rot) of five p-substituted (selenobenzoyl)morpholines was determined by dynamic 13C NMR. The activation barriers were found to range from 61.6 kJ/mol (X = NNMe2) to 75.1 kJ/mol (X = H). The ΔG≠rot values of the corresponding (thiobenzoyl)morpholines were found to be from 3.2 kJ/mol
(所述的固态结构p -bromoselenobenzoyl)吗啉(图2a)和[ p - (二甲基
氨基)selenobenzoyl]吗啉(2B)通过X射线衍射来确定。两个分子均显示平坦的
硒酰胺基团。带有对-二甲基
氨基取代基的芳环对共振稳定的贡献更大,这反映在芳环和
硒酰胺基团之间的平面角较小[53.3(1)°与81.1(1)°]以及较短的CSe键的长度[1.824(5)Å与1.840(3)Å]。CN键旋转激活的吉布斯自由能(ΔG ≠ rot)为5 p通过动态13 C NMR测定取代的(
硒代苯甲酰基)吗啉。发现活化势垒的范围为61.6 kJ / mol(X = NNMe 2)至75.1 kJ / mol(X = H)。该Δ ģ ≠腐发现相应的(
硫代苯甲酰基)吗啉的值是从3.2千焦/摩尔(X = NME 2)至5.0千焦/摩尔(X = H)降低。在这两种情况下,ΔG ≠ rot均与s̀ + p表现出极好的线性Hammett相关性。