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Hydrogen Bond: Definition, Types, and Examples

Hydrogen Bond Definition

Hydrogen Bond is a chemical bond formed due to an electrostatic link between the electronegative atom of a polar covalent bond and the slightly positive H atom of another polar covalent bond.

Molecules, atoms, or ions are held together as a compound due to chemical bonds. The major biologically significant bonds include covalent bonds, hydrogen bonds, and ionic bonds.

Characteristics Hydrogen Bond

It is a general common bond found in all biological entities that involve an H atom. A strongly electronegative atom like nitrogen, oxygen, or fluorine of a polar covalent bond attracts the hydrogen atom in the same or another molecule. This electrostatic link is due to strong dipole-dipole attraction. This type of bond can be observed in both inorganic molecules like water and in organic molecules like proteins. Associated liquids are the term given to liquids that comprise hydrogen bonds.

The dipole-dipole interaction refers to an electrostatic attraction between atoms or ions of opposite charge. A hydrogen bond can be referred to as an electrostatic attraction too that can occur between an H atom and an atom that has a lone pair of electrons that will serve as the hydrogen bond acceptor.

If the H is linked to an electronegative atom then it will act as the hydrogen bond donor and does not bind covalently with hydrogen and is termed as the proton acceptor. The atom bound to hydrogen covalently acts as a proton donor that is also a Lewis base.

The bond formed in the H bond is weak as it has only 1/20 strength of a covalent bond and is also weaker than the ionic bond. The energy of this bond equals 1 to 40 kcal/mol and varies based on the atoms, their surroundings, and their geometry. They are stronger than a Van der Waals bond.

H···Y The hydrogen bond is symbolically represented with the help of dots between the H atom (H+) and the proton acceptor that is a strongly electronegative atom.

Intermolecular vs Intramolecular Hydrogen Bonds

Separate molecules are linked with intermolecular hydrogen bond, while intramolecular hydrogen bond occurs within the same molecule. An example of an intermolecular hydrogen bond can be seen in the case of water molecules that forms H bonds with surrounding water molecules.

This is can be understood by the fact that water is a polarized molecule, the H atom of one molecule is attracted to the electronegative oxygen of the other. Various properties of water like specific heat, the heat of vaporization, high surface tension, and high boiling point can be accounted for by the H chemical bonds.

An example of an intramolecular hydrogen bond can be seen in proteins and DNA. The structure of DNA is stabilized by H bonds formed between paired nucleobases resulting in the double helix.

In biological entities, the co-existence of both types of hydrogen bonds can be seen as in cellulose where both intramolecular hydrogen and intermolecular hydrogen bonds can be observed.

Hydrogen Bond vs Covalent Bond

The electronegativity of the atoms is a differentiating factor between the H bond and the covalent bond. Unlike hydrogen bonds, in a covalent bond, both the atoms have similar electronegativity. While in the case of hydrogen bonds the proton acceptor is more electronegative.

Both kinds of bonds can be exemplified in organic compounds and structures like nucleic acids. Secondary and tertiary forms of nucleic acids and proteins are only possible due to hydrogen bonds.

Hydrogen Bond vs Ionic Bond

The biggest distinction between these 2 bonds is their strength hydrogen bond is weaker than an ionic bond. A hydrogen bond is an electrostatic chemical bond formed between an electronegative atom and an H atom of the same molecule or another molecule.

Importance of Hydrogen Bond

The hydrogen bond is a crucial bond that is responsible for the stability of the tertiary structure of proteins and of DNA that is vital for their function. This bond is important for both organic and inorganic molecules. It also helps in the polymerization of natural and synthetic organic molecules and also plays an important role in crystallization. The H bonds help reinforce the structure and stabilize linear chains in aramid fiber.

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