A Short Note on Types of Hydrogen Bonding

An electronegative atom and a hydrogen atom connected to another electronegative atom form a hydrogen bond, which is a type of attractive (dipole-dipole) contact. A hydrogen atom is always used in this bond. Between molecules and within sections of a single molecule, hydrogen bonds can form.

Hydrogen bonds are stronger than van der Waals forces, but not as strong as covalent or ionic bonds. The strength of the covalent connection produced between O and H is roughly 1/20th (5 percent). Even this frail link, though, can endure minor temperature changes. 

Between base pairs and between water molecules, hydrogen bonds are found in nucleic acids. Hydrogen and carbon atoms of distinct chloroform molecules, hydrogen and nitrogen atoms of surrounding ammonia molecules, repeating subunits in the polymer nylon, and hydrogen and oxygen in acetylacetone form this type of link. Hydrogen bonds bind a lot of organic molecules together. Bond of hydrogen:

1. Assist transcription factors in binding to DNA.
2. Assist in antigen-antibody binding.
3. Group polypeptides into secondary structures like the alpha helix and beta sheet.
4. Place the two DNA strands together and hold them together.
5. Assemble transcription factors.

Intermolecular Hydrogen Bonding

An acid’s strength is reduced when intermolecular hydrogen bonds develop. H2O is weaker than H2S, but HBr is weaker than HI. The ability to form a hydrogen bond with water is required for a chemical to be soluble in water. Hydrogen bonding can occur in any molecule with a hydrogen atom directly connected to an oxygen or nitrogen. Similar-sized molecules without a -O-H or -N-H group will always have greater boiling temperatures. In the same way that hydrogen bonding happens in ammonia, hydrogen bonding occurs in organic compounds having N-H groups. Simple molecules, such as CH3NH2 (methylamine), to big molecules, such as proteins and DNA, are all examples. This is a type of dipole-dipole interaction that happens when a hydrogen atom is bound to oxygen, nitrogen, or fluorine. The connection of molecules is caused by intermolecular hydrogen bonds. As a result, the melting temperature, boiling point, viscosity, surface tension, solubility, and other properties are typically increased. Each element to which hydrogen is bonded is both considerably negative and has at least one ‘active’ lone pair. 

Intramolecular Hydrogen Bonding

Intramolecular hydrogen bonding has a profound impact on the structure and characteristics of molecules. We look into both elements in depth in order to make this type of interaction more useful in medicinal chemistry. We derive propensities for intramolecular hydrogen bond formation of five to eight-membered ring systems of interest in drug discovery based on thorough searches in crystal structure databases. By comparing small molecule and protein ligand X-ray structures, a variety of motifs, many of which are plainly underrepresented in drug discovery, are studied in greater depth. Sets of closely related structures with and without the ability to generate intramolecular hydrogen bonds were developed, synthesised, and evaluated for membrane permeability, water solubility, and lipophilicity in order to examine implications on physicochemical attributes. Changes in these properties are found to be dependent on a delicate balance between the strength of the hydrogen bond interaction, the geometry of the newly formed ring system, and the relative energies of open and closed conformations in polar and nonpolar environments.

Intermolecular Hydrogen Bonding example

Numerous supramolecular structures have been influenced by intermolecular hydrogen bonds linking nucleobase pairs (adenine-thymine (A-T) and cytosine-guanine (C-G). However, nucleobase, nucleoside, and nucleotide-based hydrogelators are in short supply. Based on its capacity to produce G-quartet in the vicinity of monovalent cations (Na+ and K+), guanosine hydrazide has been used to make stable hydrogels. Self-assembling technologies for producing dynamic hydrogels for biological purposes have sprung up as a result of this discovery. For example, Lehn and colleagues demonstrated that nucleotide 1 can immobilise and release therapeutic molecules such as acyclovir, vitamin C, and vancomycin in a regulated manner. Similarly, Oda and colleagues created two-component hydrogels by simply mixing cationic gemini-nucleosides and their corresponding base pairs in a solution.

The authors came to the conclusion that the phenomena of multicomponent hydrogelation between two nongelator molecules is caused by a coassembly arising from Watson-Crick base-pair interaction.

Conclusion

H-bonds are directional and also have enthalpies of formation on the order of nkT at room temperature, with n 10 for weak H-bonds. As a result, they play a distinctive role in everyday life, despite the fact that this position has been under-emphasised. Their directionality enables them to be at the heart of very well molecular structures, much like covalent bonds enable atoms to assemble and construct well-defined molecules. The formation enthalpies of covalent bonds are one order of magnitude higher than H-bonds. At room temperature, these are strong connections that keep most molecules stable yet inflexible, permitting only modest amplitude vibrations of atoms around the equilibrium positions. They are largely unaffected by temperature changes. Stable H-bonded molecule assemblies, on the other hand, are flexible and evolutive because changing their structures necessitates energies that are within thermal fluctuations’ grasp. The DNA double helix is an excellent example of the stability, flexibility, and evolutionary potential that all biomacromolecules must have.