3. • Changes in chemical structure or the environment lead to
changes in the absorption spectrum of molecules and
materials
Bathochromic Shift : a shift of λmax towards lower energy or longer
wavelength (often called a red shift).
Hypsochromic Shift : a shift of λmax towards higher energy or shorter
wavelength (often called a blue shift)
Hyperchromic Shift : The shifting of molar absorptivity(absorption
intensity) towards higher values(increases).
Hypochromic shift : The shifting of molar absorptivity (absorption
intensity) towards lower values(decreases).
1
2
3
4
4. • Absorption maximum(λmax) shifted towards
longer wavelength.
Bathochromic shift
NH2
max
255 nm
max
280 nm
Benzene aniline
1
5. • Absorption maximum(λmax) shifted towards
shorter wavelength.
Hypsochromic shift
NH2
max
203 nm
max
280 nm
Anilinium ion
Aniline
NH3
H
2
6. • Absorption Intensity maximum(ɛmax) shifted
towards higher values.
Hyperchromic shift
N
N
max
3550
max
2550
2-methyl Pyridine
Pyridine
3
7. • Absorption Intensity maximum(ɛmax) shifted
towards lower values.
Hypochromic shift
max
10,500
max
19000
2-methyl biphenyl
biphenyl
4
