Kiertymäkulmat

Kiertymäkulmat, also known as torsion angles or dihedral angles, are a fundamental concept in stereochemistry used to describe the spatial arrangement of atoms within a molecule. They specifically measure the angle between two planes, each defined by three consecutive atoms. Imagine a molecule with four connected atoms, labeled A, B, C, and D. The first plane is formed by atoms A, B, and C, and the second plane by atoms B, C, and D. The kiertymäkulma is the angle between the plane containing A-B-C and the plane containing B-C-D, as viewed along the bond connecting B and C.

In organic chemistry, kiertymäkulmat are crucial for understanding molecular conformation, which refers to the different spatial arrangements a molecule can adopt through rotation around single bonds. Different kiertymäkulmat lead to distinct conformers. For example, in ethane, rotations around the central C-C bond result in staggered and eclipsed conformations, each characterized by specific dihedral angles. These conformational preferences significantly influence a molecule's physical properties, reactivity, and biological activity.

The convention for measuring kiertymäkulmat is typically the Newman projection, where the molecule is viewed along a specific bond. Angles are usually measured from 0 to 180 degrees. A positive angle often indicates a clockwise rotation (or "gauche" relationship) when moving from the front atom to the back atom, while a negative angle indicates a counter-clockwise rotation (or "anti" relationship). Understanding and quantifying these angles allows chemists to predict and explain the three-dimensional shapes of molecules.