A chromophore is a molecular fragment that absorbs specific wavelengths of visible or ultraviolet light, leading to the color we perceive in many cases.
Structure:
Chromophores generally possess double bonds, triple bonds, or aromatic systems, which allow for π-π* electronic transitions.
They have a conjugated system, meaning alternating single and double bonds.
This conjugation allows for the delocalization of π-electrons across the adjacent aligned p-orbitals, making the molecules capable of absorbing specific wavelengths of UV or visible light.
Function:
When a molecule containing a chromophore absorbs light, it results in the excitation of electrons from a ground state to an excited state.
The specific wavelength (or energy) at which this absorption occurs is determined by the nature and arrangement of the chromophore within the molecule.
Examples:
C=C (in alkenes), C=O (in ketones and aldehydes), and the aromatic systems in compounds like benzene.