What is Hydrogen Bonding? What are its types?

What is Hydrogen Bonding? What are its types?

A hydrogen Bond or so called H-bond is a force of attraction between a hydrogen atom and another atom which is electronegative which bears a lone pair of electrons. The hydrogen atom is covalently bound to an electronegative atom which is on the higher side. This interacting system can be described by Dn—H ———-Ac. Here the solid line is a polar covalent bond and the dotted line denotes hydrogen bond. The Ac here means hydrogen bond acceptor. The most common atoms which are donors and acceptors are Nitrogen, Oxygen and Florine.

Hydrogen bonds are inter molecular or intra molecular. Intermolecular means separate molecules and intra means same molecules. Many compounds like N, O and F have many chemical and physical properties which are dependent on the hydrogen bond. Specially the intermolecular bonding is responsible for high boiling point of water. The other acting hydrides are much weaker as compared to the hydrogen bond.

The intramolecular hydrogen bonding is responsible for secondary and tertiary properties of the proteins. This also plays an important role in polymer structure formation, both synthetic and natural. Depending on the nature of the hydrogen bond, their energy can vary from1 to 40 kcal/mol. They are weaker than most full covalent bonds. These types of bonds can happen in inorganic molecules such as water and organic molecules like DNA etc. Hydrogen bonds are responsible for holding materials like paper, felted wool etc.

Diagram representation for Hydrogen bond:

1. WATER

Here the dotted lines is the hydrogen bond.

General Characteristics:

1. Hydrogen bond donor: These are the hydrogen bonds which are attached to the electronegative atom and hence they are called donors. The C and H bonds only act together in the hydrogen bond when the carbon atom is bound to an electronegative substituent. Eg- Chloroform. CHCl3.
2. In a definitive hydrogen bond the atoms which are electronegative are not attached in a covalent bond with the hydrogen atom and called as proton acceptor. In the case of proton donor the one is covalently bound to the hydrogen.
3. In a Hydrogen bond the H is protic, which is basically the solvent where Hydrogen atom is bound to an oxygen atom. The donor is lewis based and the hydrogen bonds are defined by H——Y and hence certain liquids that display such hydrogen bonds are known as associated liquids. Eg- Water.
4. Let us go through some examples of hydrogen bond donors and acceptor groups. Example – Acetic acid, Here we have a hydrogen bond which is often said to be in a dipole and dipole interaction. They also show covalent bonding. The bond is strong and have direction. The covalence features are prominent and the acceptor hydrogen bonds from more electronegative donors.
5. Another example is Sulfur or Chlorine which have weaker hydrogen bonds and these are called as hydrogen atoms and can act as donors. Here the carbon is electronegative. There are several examples of weak hydrogen bonds that involves donors. These bonds are pivotal in controlling the interactions in medicinal chemistry or intra or inter molecular interactions in some sciences.

What are the 3 types of hydrogen bonds? Hydrogen bonds are classified into Weak bonds, moderate and strong bonds depending on their energy. The Weak hydrogen bonds has less polar groups in proton donors. The strong ones have high polar groups.

Hydrogen Bonds in Polymers:

The hydrogen bonds in some polymers play a very important role in making the structure of the proteins. This is applicable for both natural and synthetic proteins. They are very weak ones and hence can be easily broken down by some chemical and mechanical ways but it also retains the basic properties.

DNA:The double helix structure of the DNA is because of hydrogen bonding. Between its base pairs the strands are complimentary and are capable of replication. If we study the hydrogen bond then we know the biochemical and physiological properties.Cellulose: Here some polymers have strong bonds because of hydrogen bonds. Among all the synthetic polymers eg- Nylon where the Hydrogen bonds occur in repeat and and play a very important role in the material crystallisation. The hydrogen bonds occur between the amine and carbonyl groups. They link all the chains in it and thus make it stronger. The hydrogen bonds in both the natural and synthetic polymers make it very sensitive to humidity in the atmosphere. This is because the water molecules will diffuse into the surface of it and will make the environment difficult. Some polymers are more sensitive than others Eg- Nylon.

Proteins: The hydrogen bonds in Proteins are responsible for the stability between the subunits of the proteins. The protein backbone of the hydrogen bond is called as dehydron where it is not completely shielded from water. The Dehydrons promote the removal of water from the proteins.

Check similar QnA and clearyour doubts, refer: Organic Chemistry – Some Basic Principles And Techniques from Class 11 Chemistry – Find All the Questions & Answers

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