A torsion angle is a fundamental geometric parameter that defines the relative rotation between two planes or bonds within a molecule. It represents the angle through which one plane or bond must be rotated around a specific axis in order to align it with the other plane or bond.
In a molecule, atoms are connected by covalent bonds, which have a fixed bond length and direction. However, the atoms can still exhibit flexibility or motion around these bonds. The torsion angle measures the rotation or twist occurring along these bonds.
To define a torsion angle, four atoms in a molecule are necessary. Three consecutive atoms form a backbone or a chain, and the fourth atom is connected to the third atom. The torsion angle is measured between the planes formed by the first, second, third atoms, and the second, third, fourth atoms.
The measured angle determines the three-dimensional conformation of the molecule. Torsion angles are particularly crucial in organic chemistry as they provide information about the rotational freedom of molecular parts, affecting their stability, reactivity, and biological properties.
Torsion angles are also commonly used in computational chemistry and molecular modeling to describe and predict the conformational changes in molecules. Understanding torsion angles helps in studying molecular structures, protein folding, peptide conformation, and molecular mechanics.
In summary, a torsion angle is a geometric property that quantifies the rotation around a bond or between atoms in a molecule, influencing the molecular structure, flexibility, and various properties of the compounds.
