The Influence of Homoring Competition Effect of Substituents on the Nonclassical Hydrogen Bonding Properties in Diarylnitroketone

ABSTRACT Nonclassical hydrogen bond (NCHB) as a weak interaction force not only plays an important role in organic conversion and catalysis but also has significant implications for understanding and predicting the properties of compounds. At present, the influence of homoring competition effect of substituents on the intramolecular properties of NCHB has not been studied. In this work, 51 diphenylnitroketone XArCH=N(O)ArY (XPNY) compounds containing different substituents were chosen as model molecules, the bond energy ( E HB ) in CH⋯O and aromaticity of quasi‐aromatic ring (PDI Q ) were computed, and the chemical shifts δ H(CH⋯O) of 1 H NMR in CH⋯O were collected or measured. This work focuses on analyzing the NCHB CH⋯O hydrogen bond in compounds XPNY and explored the influence of homoring competition effect of substituents on the energy E HB of CH⋯O and chemical shift value δ H(CH⋯O) . The results show that (1) the chemical shift values δ H(CH⋯O) of CH⋯O in XPNY are abnormally large, and the values of E HB are 14.15–15.51 kJ/mol, lower than 16.74 kJ/mol, which is consistent with the characteristics of intramolecular NCHB. Therefore, it can be considered that the CH⋯O hydrogen bonds are NCHB in XPNY. (2) The substituent X in compound XPNY exhibits the homoring competition effect. (3) The aromaticity of quasi‐aromatic ring Q is the main factor affecting the E HB . The substituent X affects the E HB and δ H(CH⋯O) along different paths. This study can help understanding the impact of substituent effects on NCHB in depth.