CHROMOPHORE CONCEPT

1. CHROMOPHORE CONCEPT
PRESENTED BY;
AISWARYA.A.T
I MPharm.,
DEPARTMENT OF PHARMACY PRACTICE
GRACE COLLEGE OF PHARMACY

2. CHROMOPHORE
 Defined as any isolated covalently bonded group
that shows a characteristic absorption of
Electromagnetic radiation in the UV or visible
region.
It is a Greek word.
Chroma = “color” & phoros = “bearer”
Compound containing chromophore is CHROMOGEN
Eg: C=C, C=O, NO2

3. TYPES OF CHROMOPHORES
1. INDEPENDENT CHROMOPHORES
If one chromophore is required to impart colour
Eg: Azo group –N=N-, Nitroso group –NO-
2. DEPENDENT CHROMOPHORES
If more than one chromophore is required to impart colour
Eg: Acetone having one ketone group is colorless whereas
diacetyl having two ketone groups is yellow.

4. Groups λmax
C – C 1350
C = C 1900
C = O 1900
2800
O – H 1850
NO2 2800
C6H5( PHENYL) 1950
2500
SIMPLE CHROMOPHORIC GROUPS

5. Auxochrome
A saturated/ unsaturated group with non bonding
electrons when attached to chromophore altering both
wavelength as well as intensity of absorption.
Eg: OH, NH2, NHR, COOH, CN, Cl etc..

6. Two types:
1) Basic/positive auxochromic groups
Effective in acid solutions
Eg: OH, OR, NHR etc.
2) Acidic/negative auxochromic groups
Effective in alkaline solutions
Eg: NO, CO, CN etc.

7. CHANGESIN POSITION& INTENSITYOF ABSORPTION
For isolated chromophore groups such as –C=C- absorption
takes place at far UV which cannot be easily studied but the
position & intensity can be modified:
bathochromic
hypsochromic hyperchromic
hypochromic
200 wavelength 800
absorbance
λ max

8. BATHOCHROMIC SHIFT/ RED SHIFT
•Shift of absorption maximum towards longer
wavelength
•Due to presence of groups like OH, NH2 etc.
(auxochromes)
Eg: ethylene shows absorption at 170nm whereas
1,3-butadiene shows at 217nm.

9. HYPSOCHROMIC SHIFT / BLUE SHIFT
•Shift of absorption maximum towards shorter
wavelength
•May be caused by removal of conjugation
Eg: In Aniline, absorption takes place at 280nm.
In acidic solutions, absorption takes place at
200nm

10. HYPERCHROMIC SHIFT
Increase in intensity of absorption
By introduction of ‘auxochrome’
Eg: introduction of methyl group in position 2 of
pyridine increases intensity of absorpion from
2750 to 3560
HYPOCHROMIC SHIFT
Decrease in intensity of absorption
Eg: introduction of methyl group in position 2 of
biphenyl group causes hypochromic effect because
of distortion

11. THANK YOU!!!