Theoretical relationship
Hydrogen bond (X-H... Y) and weak force between X... Y without hydrogen atom (not including chemical bond) belong to secondary bond. The secondary bond can be determined according to the distance between atoms, nuclear magnetic resonance spectrum, spectrum and other experimental data. Chemical reaction process The transition state formed in is the intermediate or activated complex characterized by secondary bonds. The study of secondary bonds in the structure and properties of substances, biological systems and Supramolecular chemistry Play an important role in. Reflected in the molecular structure, when the distance between atoms is less than or close to the sum of the corresponding ionic radius, covalent radius or metal radius, it can be considered that chemical bonds are formed between atoms; When the distance between atoms in different molecules is the sum of the van der Waals radii, it can be considered that there is a van der Waals force between molecules; When the distance between atoms is between the range of chemical bond and van der Waals force, it can be considered that secondary bond is generated between atoms
The study of Hg-N bonds in a series of compounds found that the distance between Hg and N is continuously distributed in the range from the sum of covalent radii (about 210pm) to the sum of van der Waals radii (about 330pm). This shows that the secondary bond is universal and objective, and it also shows that the boundary between chemical bond, secondary bond and van der Waals force is difficult to be clearly defined.
Hydrogen atoms participate in a considerable part of the secondary bonds. Hydrogen bond is a typical secondary bond, and it is also the first secondary bond found and studied.
