@DrBSK @sateeshbeepala #sateeshbeepala useful to B.Sc & M.Sc chemistry students

1. Spectroscopy
Dr. B. Sateesh Kumar
M.Sc., CSIR-JRF, Ph.D
Assistant Professor in Chemistry
GDC TKL
5
Bands in UV
Spectroscopy
&
Conjugation Effect

2. Conjugation effect
@DrBSK

3. Explanation
Energy gap more
leads to
Low wavelength
Energy gap less
leads to
high wavelength
@DrBSK

4. Bands in UV spect.
• K-band
• R-band
• B-band
• E-band
@DrBSK

5. K-band
• Due to: pi to pi* transition
• It is observed in conjugate double
compounds
• Intensity : higher (>104 )
@DrBSK

6. R-band
• Due to: n to pi* transition
• It is observed in carbonyl
compounds
• Intensity : lower (below 100 )
• Forbidden transition
@DrBSK

7. B-band
• Due to: pi to pi* transition
• It is observed in Aromatic and
hetero aromatic compounds
• Intensity : Good
• Benzene shows 255nm
• Range : 230nm-270nm
@DrBSK

8. E-band
• Due to: pi to pi* transition
• It is observed in 3 ethylenic double
bonded compounds(Benzenoid
systems)
• Benzene E1 Band at 184nm - Higher
intensity(50000)
@DrBSK

9. See you in
part-6
windward-Fischer rules