Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, United States.
J Phys Chem A. 2023 Jun 1;127(21):4695-4703. doi: 10.1021/acs.jpca.3c02049. Epub 2023 May 20.
Quantum calculations study the potential of an intramolecular H-bond between the halogen atom (X) of a halobenzene and a substituent placed ortho to it, to amplify the ability of X to engage in a halogen bond (XB) with a Lewis base. H-bonding substituents NH, CHCHOH, CHOH, OH, and COOH were added to halobenzenes (X = Cl, Br, I). The amino group had little effect, but those containing OH increased the CX···N XB energy to a NH nucleophile by about 0.5 kcal/mol; the increment associated with COOH is larger, nearly 2 kcal/mol. These energy increments were approximately doubled if two such H-bonding substituents are present. Combining a pair of ortho COOH groups with an electron-withdrawing NO group in the para position has a particularly large effect, raising the XB energy by about 4 kcal/mol, which can amount to as much as a 4-fold magnification.
量子计算研究了卤苯中卤素原子 (X) 与邻位取代基之间形成分子内氢键的潜力，以增强 X 与路易斯碱形成卤素键 (XB) 的能力。将氢键取代基 NH、CHCHOH、CHOH、OH 和 COOH 添加到卤苯中（X = Cl、Br、I）。氨基的影响较小，但含有 OH 的取代基将 CX···N XB 能量增加到 NH 亲核试剂的程度约为 0.5 kcal/mol；COOH 的增量更大，接近 2 kcal/mol。如果存在两个这样的氢键取代基，这些能量增量大约增加一倍。在对位引入一对邻位 COOH 基团和一个吸电子的 NO 基团具有特别大的影响，将 XB 能量提高了约 4 kcal/mol，这相当于放大了 4 倍。
