This document discusses optical rotatory dispersion (ORD) and circular dichroism (CD). ORD measures the change in specific rotation of plane-polarized light with wavelength for optically active compounds. CD measures the difference in absorption of left and right circularly polarized light. Key differences are that ORD uses plane-polarized light while CD uses circularly polarized light. ORD graphs plot specific rotation versus wavelength while CD graphs plot molar ellipticity versus wavelength. Both techniques provide information about molecular structure and can be used to analyze proteins, nucleic acids, and other biomolecules.

1. Optical Rotatory Dispersion &
Circular Dichorism

2. CONTENT
 ORD
 PRINCIPLE
 FUNDAMENTAL OF ORD
 CD
 COTTON EFFECT
 ORD CURVES
 APPLICATION
 DIFFERENCE B/W ORD & CD
 CONCLUSION

3. ORD
• ORD is technique related to the optical activity
• Rate of change of specific rotation with change in wave length
• Optical rotation caused by compound changed with wavelength of
light was first denoted by Biot in 1817

4. FUNDAMENTAL OF ORD
• Plane polarized light
• Optical activity
• Specific rotation
• Circular birefringence
• Optical rotation
• Elliphicity

5. Plane polarized light
• Light from ordinary lamp consists of waves vibrating in many
different planes
• It is passed through Polaroid lens it is found to be vibrate in
one plane is said to be plane polarized light

7. OPTICAL ACTIVITY
• The compounds which are having the ability to rotate the
plane of polarized light are called optical active compound
• This property of compounds is called optical activity
• Measured by Polarimeter
• Dextrorotatory
• Levorotatory

9. SPECIFIC ROTATION
• The specific rotation ([α]) is an intensive property of
a chemical compound, defined as the change in orientation of
the plane of linearly polarized light as this light passes through
a sample with a path length of 1 decimeter and a sample
concentration of 1 gram per 1 millilitre
• It is denoted by [α]

10. CIRCULAR BIREFRINGENCE
• Birefringence is the optical property of a material having
a refractive index that depends on the polarization and
propagation direction of light
• α= (nL-nR)π/ α

11. CIRCULAR DICHORISM
Some material posses special properties of absorption of the light
circularly light to different extent than the right circulary
polarized light
Chiral or asymmetric compounds produce CD spectrum

12. COTTON EFFECT
This phenomenon was
discovered in 1895
by the French
physicist Aimé
Cotton
Combination of
circular dichorism &
circular birefringence

13. ORD CURVES
• Plain curves
• Anomalous curves
• single cotton effect curves
• multiple cotton effect curve

14. PLAIN CURVES
• Normal smooth curves
• Do not cross the zero rotation line
• e.g.:- alcohols hydrocarbons

15. ANOMALOUS CURVES
• Shows no. of extreme peaks & troughs

16. SCEC & MCEC
• Two or more peaks &
trough
• e.g. ketosteroids
• camphor

17. APPLICATION
• CD/ORD of protein
• Qualitative analysis of molecules
• Enzyme co-factor evaluation
• CD/ORD of proteins
• CD as finger printing
• CD/ORD of nucleic acids
• CD of B-DNA is different as compared to A-DNA
• Evidence for base stacking

18. CD/ORD of proteins
• e.g:- L-lysine
• Positive CD at 217nm
• Negative CD at 197nm
• Random coil :- ph 5.2
• Alpha helical :- ph 11.0

19. QUALITATIVE ANALYSIS
• Measuring by the specific rotation
• α =100 α /lc
•
• m =M α /100

20. Enzyme co-factor evaluation
• Teng et.al carried out the spectrum of enzyme p-
hydroxybenzoate

21. CD as finger printing
• It acts as finger printing technique for trace amount of
carbohydrate meterial
• E.g. dermatan sulphate
• heparitin sulphate
• E.g :- pectin in the presence of citric acid& sucrose

22. CD of B-DNA & A-DNA

23. BASE STACKING
• ORD spectrum of Polycytidylic acid shows at 292nm is
35,160deg/M/cm
• HELICITY DETERMINED BY
• Formaldehyde
• Ethylene glycol

24. DIFFERENCE B/W ORD & CD
ORD CD
PLANE POLARIZED LIGHT
DISPERSIVE PHENOMENA
PLANE POLARIZED IS USED & IS NOT
CONVERTED TO ELLIPTICAL LUGHT
GRAPHS ARE OBTAINED BY SPECIFIC
ROTATION V/S WAVELENGTH
CIRCULARLY POLARIZED LUGHT
ABSORPTIVE PHENOMENA
CIRCULAR POLARIZED LIGHT IS USED
& IS CONVERTED TO ELLIPICITY
GRAPHS ARE OBTAINED MOLAR
ELLIPICITY V/S WAVE LENGTH

25. INSTRUMENTATION OF ORD
• Light source
• Monochromator
• Polarizer
• Analyzer
• Sample tube
• photomultiplier

26. INSTRUMENTATION OF CD
• Light source
• Polarizer
• Sample tube
• Photomultiplier
• Recorder

27. CD SPECTROSCOPE

29. CD/ORD
 Simple and quick experiments
 No extensive preparation
 Relatively low concentrations/amounts of sample
 Microsecond time resolution
 Any size of macromolecule
 Better resolution
 Better sensitivity
 Easier to assign

30. REFERENCE
 WWW. Science direct.com
 WWW.notes .com
 Principles & techniques by Avinash Upadhyay
 WWW.scribd.com

31.  THANK YOU