Infrared spectroscopy is fundamental tool for structural elucidation of new drugs/compounds.The absorption of IR radiation causes transition in vibrational level of molecules which accompained by an change in dipole-moment.

1. APPLICATIONS OF NIR AND
2-D NMR IN STRUCTURAL
ELUCIDATION OF POLYMERS
Presented By :
Surendra negi
M.pharm-1st year
(pharmaceutics)

2. Contents
 Near infrared spectroscopy(NIR)
 Types of NIR spectroscopy
 Applications of NIR
 Two Dimensional (2-D) NMR spectroscopy
 Types of 2-D NMR
 Applications of 2D NMR spectroscopy

3. Near infrared spectroscopy(NIR)
 Infrared spectroscopy is fundamental tool for
structural elucidation of new drugs/compounds.
 The absorption of IR radiation causes transition in
vibrational level of molecules which accompained by
an change in dipole-moment.
 The IR region divided into three main part.
Region Energy(KJ/mol) wavenumber
(cm-1)
Wavelength
(µm)
NIR 150-50 12,800-4000 0.78-2.5
MIR 50-2.5 4000-200 2.5-50
FIR 2.5-0.1 200-10 50-1000

4. Near infrared spectroscopy(NIR)
• The NIR region of spectrum extend from wavelength
770nm-2500nm(13000-4000cm
-1
).
• Absorption bands in this region are overtones or
combination of fundamental stretching vibrational
bands. And bands generally associated with
hydrogen bond.
• Bonds involved are usually C-H,N-H and O-H.
• Because the bands are overtones or combination, their
molar absorptivities are low and detection limits are
on the order of 0.1%

5. Types of NIR spectroscopy
 NIR absorption spectroscopy
 NIR reflectance spectroscopy: The absorptivity of NIR band
is 1000 times less than MIR so NIR beam penetrate deeper
into a sample and gives more representative analysis.
Applications of NIR
(1). NIR absorption spectroscopy
 NIR less use in identification but used in quantitative
analysis of drugs/compounds containing hydrogen
bonding.
 Determination of water in various samples like
glycerol, hydrazine, organic film.
 Determination phenol, org.acids, alcohols etc.

6.  Determination of primary, secondary amines in presence
of tertiary amines.
(2)NIR reflectance spectroscopy
 Most important tool for routine quantitative analysis of
solids like wood, components of polymer
 Determination of proteins, moisture, oils, lipids in food
and grain industry.

7. Two Dimensional (2-D) NMR
spectroscopy
• Introduction
• 2D NMR is a set of NMR methods which gives a data plotted in
a space defined by two different frequency axes.
• A conventional 1H NMR spectrum has a frequency axis and
an intensity axis whereas in 2-D NMR spectrum has two
frequency axes and one intensity axis.
• It includes:
• (a).COSY(Correlated SpectroscopY)
• (b).HETCOR(HETeronuclear CORrelation)
• (c).Two-D 13C INADEQUATE
• (d).space correlation method
I. NOESY
II. ROESY
•

8. (a).COSY(Correlated SpectroscopY)
 It is commonly used 2-D NMR in which 1H-1H shift
correlation in both frequency axes
show 1H chemical shift. So also known as 1H-1H shift
correlation spectroscopy.
 COSY identified pairs of protons which are coupled
together.
 COSY spectrum is like mountain range viewed from air
(stack plots) but not used in study of compounds ,here
used slices of each mountain ( contour plots )

9. Contour
plot

10. COSY spectrum of m-dinitrobenzene(cross peak correlation)
NO2
NO2
HH
H
H

11. (b).HETCOR(HETeronuclear CORrelation):This shows
13C-1H shift correlation used to detect directly bounded 13C-1H
atoms.
(c)Two-D 13C INADEQUATE: Detect 13C-13C shift
correlation.
(d).space correlation method: Spectrum in this method is
similar to COSY but cross peaks connect resonance from nuclei
that are close instead of connected through bonds.
(i).Nuclear overhaused effect spectroscopy(NOESY)-For large
molecules e.g. isovanilline
(ii).Rotational correlation(ROESY)-For medium size molecules.
These both are used for space effect in stereochemical analysis.

12. Applications of 2D NMR spectroscopy
This provides the view of 2-D as well as 1-D 1H spectra too.
Two-D NMR spectroscopy leads to development of-
(i).Chemical shift and coupling constant into 2-D
(ii).To resolve overlap of resonance which enable the
correlation of interacting nuclei to be determined. Thus the 2-D
NMR used for complex structure analysis.
To determine which two protons are coupling together and their
coupling pattern i.e,geminally or vicinally coupled( by cosy).
NOESY and ROESY both are used for space effect in
stereochemical analysis.

13. References
 Skoog D.K, West D.M & Holler F.J, fundamental of
analytical chemistry ,7th edition philadelphia, page
no.422
 Kalsi P.S, Spectroscopy of organic compounds , 6th
edition, New age publiction(p) Ltd. Publiser , page
no.342
 Chatwal G.R, Instrumentation method chemical
analysis , 5th edition ,Himalay publishing house,page
no2.29-2.82