Notes On Hydrogen Bonding

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HYDROGEN BOND By- Abhinav priyadarshi (IPM2013005) Shivam Kumar Arya (IPM2013122)
Definition of Hydrogen Bonding-
Hydrogen bond is the interaction between a hydrogen atom from a molecule and an another atom or a group of atom which may be of the same or a different molecule.
Example-
In general a hydrogen bond is depicted as-
Let X–H be a molecule in which an atom X is more electronegative as compared to H, then the bond between X-H is hydrogen bond. For a hydrogen bond X–H•••Y–Z
( hydrogen bond here is depicted as X–H•••Y–Z, the three dots …show more content…

In a hydrogen bond the donor is usually the atom to which the hydrogen atom participating in the hydrogen bond is covalently bonded, and also it is mostly a strong electronegative atom such as N, F, or O. The acceptor of hydrogen is the neighboring electronegative ion or molecule, and also it must possess a lone electron pair in order to form a hydrogen bond.

Reasons for the occurance of Hydrogen Bonding
As the hydrogen donor is electronegative in nature, it attracts the covalently bonded electron pair closer and closer to its nucleus, and hence away from the hydrogen atom. The hydrogen atom is therefore is left with a partial positive charge, resulting in a dipole-dipole attraction between the hydrogen atom bonded to donor, and also the lone electron pair on the acceptor. This results in a hydrogen bonding.( see the Interaction Between Molecules With Permanent Dipole) Characteristics of hydrogen bonds
1. The pka of x–h and the pkb of y–z is related directly with the energy of the hydrogen bond formed between them.
2. The hydrogen bonds are the partially activated precursors and are also involved in proton transfer …show more content…

Hydrogen bonds helps transcription factors binds with one another
6. Hydrogen bonds helps transcription factors bind with the DNA
Types of Hydrogen Bonding-
Hydrogen bonds can be classified into two types; Intermolecular hydrogen bonding Intramolecular hydrogen bonding.
Intermolecular hydrogen bonding-
This bonding happens when the hydrogen bonding is between H-atom of one molecule and an atom of any electronegative element of another molecule. For ex (i) hydrogen bonding between the molecules of hydrogen fluoride. (ii) hydrogen bonding in alcohols or molecules of water.
Intermolecular hydrogen bonding leads to association of molecules. Therefore, it generally increases the melting point, boiling pt., viscosity, surface tension, solubility, etc.

Intramolecular hydrogen bonding-
The bond formed between the hydrogen atom and an atom of any electronegative element (F, O, N) , of the same molecule.
Intramolecular hydrogen bonding leads to the cyclisation of the molecules and hinders their association. Consequently, the impact of this bonding on the physical properties is negligible. For ex, intramolecular hydrogen bonds are present in molecules such as ortho-nitrophenol, ortho-nitrobenzoic acid, etc. Water hydrogen

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