Chromophore groups are the functional groups of the molecule responsible for absorption. Mainly they are: carbon-carbon double and triple bonds, aromatic systems, carbonyl group, imino (C=N), diazo (N=N), nitro and CY bonds (Y is an atom with lone pairs).

Auxochromic groups are substituents on the chromophore and alter $\lambda_{max}$ and/or $\epsilon_{max}$. The methyl, halogen, hydroxy, alkoxy, and amino groups are auxochromes.

Auxochrome groups have the following effects on chromophores:

• bathochromic displacement. The absorption of the chromophore is shifted towards longer wavelengths.
• Hypsochromic displacement. The absorption of the chromophore is shifted towards shorter wavelengths.
• Hypsochromic effect. $\epsilon_{max}$ increases, presenting the band with greater intensity.
• hypochromic effect. $\epsilon_{max}$ decreases, decreasing the intensity of absorption.