Definition Of Hydrogen Bond
It is a special kind of bond present between small sized highly electronegative atom such as N, O, F and hydrogen atom of a neighbouring molecule
More About Hydrogen Bond
- A hydrogen bond is the electromagnetic attractive interaction between polar molecules, in which hydrogen (H) is bound to a highly electronegative atom, such as nitrogen (N), oxygen (O) or fluorine (F)
- Although hydrogen bonding is regarded as being limited to N, O and F; but species such as Cl may also participate in hydrogen bonding
- Energy of hydrogen bond varies between 10 to 100
- This is quite a significant amount of energy; therefore, hydrogen bonds are powerful force in determining the structure and properties of many compounds, for example proteins and nucleic acids
- Strength of the hydrogen bond is determined by the columbic interaction between the lone-pair electrons of the electronegative atom of one molecule and the hydrogen atom of other molecule
- Molecules also exert repulsive forces on one another
- When two molecules are brought into close contact with each other, the repulsion between the electron clouds and that between the nuclei of two molecules comes into play
- Magnitude of the repulsion rises very rapidly as the distance separating the molecules decreases
- This is the reason that liquids and solids are hard to compress
- In these states molecules are already in close contact; therefore they resist further compression; as that would result in the increase of repulsive interactions
- When water molecules are close together, their positive and negative regions are attracted to the oppositely-charged regions of nearby molecules
- The force of attraction, shown here as a dotted line, is called a hydrogen bond. Each water molecule is hydrogen bonded to four others
- The hydrogen bonds that form between water molecules account for some of the essential — and unique — properties of water
- The hydrogen bond is often described as an electrostatic dipole-dipole interaction
- Hydrogen bond also has some features of covalent bonding: it is directional and strong, produces interatomic distances shorter than sum of van der Waals radii, and usually involves a limited number of interaction partners, which can be interpreted as a type of valence
- Liquids that display hydrogen bonding are called associated liquids
