What is a Hydrogen Bond?

The hydrogen atom and the electronegative atom X are covalently bonded. If it is close to the electronegativity Y (OFN, etc.) with a large electronegativity and a small radius, hydrogen is used as the medium between X and Y to generate XH ... Y form. A special type of intermolecular or intramolecular interaction is called hydrogen bonding. [X and Y can be hydrogen bonds between molecules of the same type, such as water molecules; or hydrogen bonds between molecules of different types, such as ammonia monohydrate molecules (NH ₃ · H ₂ O)].

In protein

Hydrogen bonds are usually represented by XH ... Y. Among them, X is connected to hydrogen by a covalent bond (or ionic bond), which has a high electronegativity and can stabilize a negative charge. Therefore, hydrogen is easily dissociated and has an acidity (proton donor). While Y has a higher

Between the same molecules

HF is taken as an example to illustrate the formation of hydrogen bonds. In the HF molecule, due to the

The bonding energy of hydrogen bond is 2-8

Hydrogen bonds are usually formed in the liquid state, but sometimes they can continue to exist in some

Effect of hydrogen bonding on melting and boiling points of compounds

Analysis of the concept of hydrogen bonding and intermolecular forces

Regarding hydrogen bonding, the most controversial discussion in the forum lies in the different authors' debate on the relationship between hydrogen bonding and intermolecular forces.

The traditional definition defines the intermolecular force as: "weak electrostatic interaction caused by the permanent dipole and transient dipole of a molecule". With the deepening of research, many phenomena that could not be explained by the existing mechanism of intermolecular forces have been discovered. Like halogen bonds, organic mercury halides are observed in the molecule

The definitions of the hydrogen bonds discussed above are all traditional Pauling definitions, and in 2011 IUPAC gave a new definition .

Hydrogen bonding is the attractive force formed between a hydrogen atom bonded to one molecule or molecular fragment X-H and another atom or atomic group. There are two types of intermolecular hydrogen bonding and intramolecular hydrogen bonding. Stronger than hydrogen. Can be expressed as X-H ... Y-Z. "..." is a hydrogen bond. X-H is a hydrogen bond donor, Y is a hydrogen bond acceptor, and Y can be a molecule, an ion, and a molecular fragment. The acceptor Y must be electron-rich. It can be a Y atom containing a lone pair of electrons or a Y molecule containing a bond. A symmetrical hydrogen bond is formed when X and Y are the same atom. ^[2]

Hydrogen bond shooting

The National Nanoscience Center of the Chinese Academy of Sciences announced on November 22, 2013

the study

For the first time in the world, a "photograph" of a hydrogen bond was taken, real-time imaging of the hydrogen bond was realized, and it provided intuitive evidence for the "nature of hydrogen bonding", which has been debated in the chemical community for more than 80 years. This not only advances human understanding of the micro world a big step, but also provides a more accurate method for research on the molecular and atomic scales.

This result was published in the journal Science recently and was evaluated as "a pioneering discovery, truly amazing experimental measurement". "It is an outstanding and exciting work with far-reaching significance and value".

The research was carried out in collaboration with an experimental team led by Qiu Xiaohui, a researcher at the National Nanoscience Center, and Cheng Zhihai, an associate researcher, and a theoretical calculation group led by Ji Wei, an associate professor in the Department of Physics at Renmin University of China. The research team led by Qiu Xiaohui innovated the core components of a non-contact atomic force microscope, a microscope that specializes in the internal structure of molecules and atoms, greatly improving the accuracy of this microscope, and finally directly observed hydrogen bonding for the first time. Provides intuitive evidence. In addition, it is said that hydrogen bonding is expected to resolve the Mpamba phenomenon.

High-resolution photos of hydrogen bonds can help scientists understand its nature, which in turn lays the foundation for controlling and utilizing hydrogen bonds. Based on this, we may artificially affect or control the structure of water, DNA, and proteins in the future, and living organisms and the environment in which we live may also change as a result. For example, hydrogen bonds support the double helix structure of DNA. Hydrogen bonds can also be undone and duplicated, which plays a very important role in life inheritance. ^[4]

Related hydrogen bonding reports

During the year of 2013, from the molecular structure to the distant planet, the scientific community continued to bring

Hydrogen bond

There are many surprises, here are the annual pictures selected by Nature. Using an atomic force microscope, Qiu Xiaohui, a Shaoxing scientist from the Chinese Academy of Sciences, and his teammates successfully captured an image of hydrogen bonding for the first time. The yellow bonds in the picture are the hydrogen bonds. ^[5]