Soloviev Daniil O, Hanna Fergal E, Misuraca Maria Cristina, Hunter Christopher A
Yusuf Hamied Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
Chem Sci. 2022 Oct 3;13(40):11863-11868. doi: 10.1039/d2sc04271a. eCollection 2022 Oct 19.
Formation of a H-bond with an amide carbonyl oxygen atom increases the strength of subsequent H-bonds formed by the amide NH, due to polarisation of the bond. The magnitude of this effect has been quantified by measuring association constants for the formation of 1 : 1 complexes of 2-hydroxylbenzamides with tri--butyl phosphine oxide. In 2-hydroxybenzamides, there is an intramolecular H-bond between the phenol OH group and the carbonyl oxygen atom. Comparison of the association constants measured for compounds with and without the 2-hydroxy group allows direct quantification of the effect of the intramolecular H-bond on the H-bond donor properties of the amide NH group. Substituents were used to modulate the strength of the intramolecular and intermolecular H-bonds. The presence of an intramolecular H-bond increases the strength of the intermolecular H-bond by more than one order of magnitude in -octane solution. The increase in the H-bond donor parameter used to describe the amide NH group is directly proportional to the H-bond donor parameter of the phenol OH group that makes the intramolecular H-bond. These polarisation effects will lead to substantial cooperativity in complex systems that feature networks of non-covalent interactions, and the measurements described here provide a quantitative basis for understanding such phenomena.
与酰胺羰基氧原子形成氢键会增强酰胺 NH 随后形成的氢键强度，这是由于键的极化作用。通过测量 2-羟基苯甲酰胺与三丁基氧化膦形成 1:1 配合物的缔合常数，已对这种效应的大小进行了量化。在 2-羟基苯甲酰胺中，酚羟基与羰基氧原子之间存在分子内氢键。比较有和没有 2-羟基的化合物所测得的缔合常数，可以直接量化分子内氢键对酰胺 NH 基团氢键供体性质的影响。使用取代基来调节分子内和分子间氢键的强度。在正辛烷溶液中，分子内氢键的存在使分子间氢键的强度增加了一个多数量级。用于描述酰胺 NH 基团的氢键供体参数的增加与形成分子内氢键的酚羟基的氢键供体参数成正比。这些极化效应将导致在具有非共价相互作用网络的复杂系统中产生显著的协同作用，此处描述的测量为理解此类现象提供了定量基础。
