I have presented an overall overview on IR spectroscopy includings its different applications.

1. IR Spectroscopy in Organic
Chemistry
Shubham Gupta
Presented by :
M.Sc. IV Sem (Organic Chemistry)
Enrollment No. – U1775175
Dr. Mohammad Saquib
Department of Chemistry
University of Allahabad
Prayagraj (Allahabad) - 211002
Under the supervision of :

2. IR SPECTROSCOPY
 Concerned with the study of absorption of infrared
radiation, which causes vibrational transition in
the molecule.
 Thus also known as Vibrational spectroscopy.
 Mainly used to determine the type of functional
groups present in an organic compound.

3. PRINCIPLE OF IR SPECTROSCOPY
Molecules are made up of atoms linked by chemical bonds. The movement
of atoms and the chemical bonds look like spring and balls(vibrations).
This characteristic vibration are called Natural frequency of vibration
Change in dipole moment is required
Applied infrared frequency = Natural frequency of vibration

4. INFRARED REGION

5. Symmetric stretching Asymmetric stretching
Scissoring Rocking
Wagging Twisting
TYPE OF MOLECULAR VIBRATIONS
1. https://en.wikipedia.org/wiki/Infrared_spectroscopy

6. Fourier Transformer infrared spectrophotometer (FTIR)
The most modern infrared spectrometer is FTIR.
The design of the optical pathway produces a pattern called
an interferogram.
Interferogram is a complex signal, but its wave-like pattern
contains all the frequencies that make up the infrared
spectrum.
FTIR spectroscopy is a rapid, very sensitive, cost-effective,
and easy-use technique.

7. IR Absorptions Bands

8. applications in organic chemistry
Determination of molecular structure: IR is used along with
other spectroscopic techniques for this purpose. Identification is
done based on position of absorption bands in the spectrum.
E.g.: C=O at 1717 cm-1. Absence of band of a particular group
indicates absence of that group in the compound.
Identification of a compound: It can be done by comparing
the spectrum of sample and spectrum in database
8

9. Detection of impurities
Determined by comparing sample spectrum with the spectrum of
pure reference compound. E.g..: ketone impurity in alcohols.
Detection is favored when impurity possess a strong band in IR
region where the main substance do not possess a band. E.g.
:Impurity in bees wax (with petroleum wax)
Protein Quantitation: IR spectroscopy is one of the most well
established techniques for the analysis of protein structure
Isomerism in organic chemistry

10. Progress of A chemical reaction- It can be followed by
drawing an aliquot and checking the IR spectra of a particular
functional group.
OH frequency 3570 cm-1 decrease and C=O frequency appears
at 1725 cm-1

11. Much of the evidence that is left at a crime scene
consists of organic compounds like Paint, ink, sweat,
fuels, and hair can be identified.
In determining the blood alcohol content.
Old paintings, documents , ink and change in ink of a
document.
Process Monitoring and Industrial Hygiene
FORENSIC AND ALLIED APPLICATIONS

12. OTHER APPLICATIONS
Determination of unknown contaminants, in industry,
using FTIR.
 Determination of cell walls of mutant & wild type plant
varieties using FTIR.
 Biomedical studies of human hair to identify disease
states (recent approach).
 Identification of odor and taste components of
food.
 Determine atmospheric pollutants from atmosphere
itself.
 Detection of leakage in natural gas and crude oil.

13. STRENGTHS AND LIMITATIONS
• IR spectroscopy alone cannot determine a structure.
• Some signals may be ambiguous.
• The functional group is usually indicated.
• The absence of a signal is definite proof that the
functional group is absent.
• Correspondence with a known sample’s IR
spectrum confirms the identity of the compound.

14. RECENT DEVELOPMENTS
Development of miniature IR spectroscopy that can be
used for personal everyday uses by embedding with
smartphones and gadgets.
Development of 2D IR offers a myriad of different
applications including isotope labeling, studies of
biological species, the investigation of proteins,
peptides, and hydrogen bond dynamics and also the
study of nanocrystalline thin films
1. Shim, S.H.; Gupta, R.; Ling, Y.L.; Strafeld, D.B.; Raleigh, D.P.; Zanni, M.T. Two-dimensional IR
Spectroscopy and Isotope Labelling Defines the Pathway of Amyloid Formation with Residue
Specification. PNAS. 2009, 106, 6614-6619.
2. Kim, Y.S.; Hochstrasser, R.M. “Applications of 2D IR Spectroscopy to Peptides, Proteins, and
Hydrogen-Bond Dynamics” J. Phys. Chem. 2009, 113, 8231-8251.

15. Thank You!!