Hydrogen-bonding

Hydrogen-bonding is a type of attractive intermolecular force that occurs when a hydrogen atom covalently bonded to a highly electronegative atom (like oxygen, nitrogen, or fluorine) experiences attraction to another nearby electronegative atom. This interaction is weaker than covalent or ionic bonds, but stronger than van der Waals forces. It's crucial in determining the physical and chemical properties of many substances, especially water and biological molecules, influencing melting points, boiling points, and the structure of proteins and DNA. The donor molecule provides the hydrogen, while the acceptor molecule possesses the electronegative atom attracting it.

Hydrogen-bonding meaning with examples

• Water's high boiling point is largely due to extensive Hydrogen-bonding between water molecules. Each molecule can form multiple hydrogen bonds with its neighbors, requiring significant energy to overcome these attractions when changing state from liquid to gas. This property is vital for life and makes water an ideal solvent.
• The secondary structure of proteins, such as alpha helices and beta sheets, is stabilized by hydrogen-bonds between the amino acid backbone. These bonds dictate the three-dimensional shape of the protein, affecting its function. Disruptions to these hydrogen bonds through changes in temperature or pH can lead to denaturation.
• DNA's double helix structure is held together by hydrogen-bonds between complementary base pairs (adenine with thymine, and guanine with cytosine). These bonds allow for precise base pairing and are responsible for the storage and transfer of genetic information, facilitating DNA replication and transcription.
• The high surface tension of water is a direct result of hydrogen-bonding. Water molecules at the surface experience a net inward pull, leading to a minimization of the surface area. This property allows small insects to walk on water, and it's critical in the formation of droplets.
• Hydrogen-bonding contributes to the solubility of alcohols in water. The hydroxyl (-OH) group in alcohol molecules can form hydrogen bonds with water molecules, allowing the alcohol to mix with water. The larger the hydrocarbon portion of the alcohol, the less soluble it becomes.