A number of 5‐acyl rhodanines and thiorhodanines with bulky acyl groups (pivaloyl and adamantoyl), not previously available, have been synthesized. The compounds are shown to exist in the enol form. Structures have been calculated using both the MP2 approach and the B3LYP‐GD3BJ functional and the 6‐311++G(d,p) basis set. Hydrogen bond energies are estimated by subtracting energies of a structure with the OH group turned 180° from those of the intramolecularly hydrogen‐bonded one. Properties such as OH chemical shifts, two‐bond isotope effects on 13C chemical shifts, electron densities at the bond critical point from atoms in molecules analysis, and the hydrogen bond energies show that the sterically hindered compounds have stronger hydrogen bonds than methyl or isopropyl derivatives. The combination of oxygen and sulfur derivatives enables a detailed analysis of hydrogen bond energies.

中文翻译：

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涉及 C=S 基团的强分子内氢键和空间效应。核磁共振和计算研究

已经合成了许多以前无法获得的具有庞大酰基（新戊酰基和金刚酰基）的 5-酰基若丹宁和硫代罗丹宁。这些化合物显示为以烯醇形式存在。已使用 MP2 方法和 B3LYP-GD3BJ 泛函和 6-311++G(d,p) 基组计算结构。氢键能是通过从分子内氢键合结构的能量中减去 OH 基团旋转 180° 的结构的能量来估算的。OH 化学位移、双键同位素对 13C 化学位移的影响、分子分析中原子键临界点处的电子密度以及氢键能量等特性表明，空间位阻化合物比甲基或异丙基衍生物具有更强的氢键.