Hydrogen bonds within one molecule, such as in o-nitrophenol, lower its boiling point.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
Intramolecular hydrogen bonding occurs when a hydrogen bond forms between two groups within the same molecule rather than between separate molecules. Because the bonding is internal, the molecule has fewer sites available for bonding to its neighbours, which reduces its intermolecular attraction. As a result, intramolecular hydrogen bonding typically lowers boiling point, increases volatility and can change solubility in water. It is important in stabilizing secondary structures of proteins and in chelate rings that bind metal ions. Its presence can be detected by changes in the spectroscopic behaviour of the groups involved.
Key ideas: Typical geometry: a six-membered ring including the hydrogen. Ortho isomers with OH adjacent to C=O or NO2 (o-nitrophenol, salicylaldehyde, salicylic acid) form it. Effects: lower boiling point and melting point than para isomers, better solubility in nonpolar solvents, lower water solubility, and increased acidity differences. Also stabilizes enol forms like acetylacetone.
Common mistakes and connections: Students assume more hydrogen bonding always means higher boiling point, ignoring that internal bonds do not link molecules together. Another error is claiming ortho and para isomers have the same properties. Links to protein secondary structure, steam distillation, enol content and chelate rings.
The ortho isomer hydrogen bonds internally, so fewer intermolecular bonds form and it melts far lower than the meta and para isomers. The interactive lesson shows this as a live animation or chart.
o-Nitrophenol forms an internal hydrogen bond and is steam volatile, while p-nitrophenol forms intermolecular bonds and is not.
Hydrogen bonds within one molecule, such as in o-nitrophenol, lower its boiling point.
Intramolecular Hydrogen Bonding is a advanced topic in Bonding & Molecular Structure. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Bonding & Molecular Structure first: Ion-Dipole Forces, Dipole-Induced Dipole Forces, Boiling Point and Intermolecular Forces.
The next topics in Bonding & Molecular Structure are Water's Anomalous Properties and Covalent Network Solids.
Yes. The interactive lesson includes a self-check question on Intramolecular Hydrogen Bonding, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Intramolecular Hydrogen Bonding is topic 77 of 104 in Bonding & Molecular Structure.