introduction, Region of IR, mode of vibration, application of IR

1. INFRARED
SPECTROSCOPY
Presented by-
Zakiya usmani
M.Pharm 1st year
pharmacognosy
Jamia hamdard

2.  infrared spectroscopy (IRspectroscopy or vibrational
spectroscopy) involves the interaction
of infrared radiation with matter. It covers a range of
techniques, mostly based on absorption
spectroscopy.
 IR spectroscopy conduct with an instrument called
infrared spectrometer to produce an IR spectrum.
Theory
The ir region of the electromagnetic spectrum may be
into devide into three region
1. Near IR region (Overtone region) visible to 0.8-
2.5μm wave number (λm) 12500-4000cm-1
2. Middle IR (vibration rotation region) visible to
2.5-50μm wave numebr (λm) 4000-200cm-1
INTODUCTION

3. CONTD..
3. Far IR region (Rotation region) visible to 50-
1000μm. Wave number λm 200-10cm-1
o The absorption of IR radiation does follow beer
law.The technique is based upon a simple fact
that a chemical shows marked selective
absorption in IR region. After absorption of IR
radiation the molecule of chemical substance
vibrate at any rates of vibration giving rise to
closed packed absorption band called IR
spectrum.
o Band position in spectrum may be expressed by
wave number.

4. MODES OF VIBRATION
 Normal vibration can be divided into two
principal groups
1. Stretching vibration - in this type of
vibration the atom move essentially along
with bond axis so that the bond length
increases or decreases preodically
2. Bendin vibration- also known as
deformation. In this type there occur a
change in band angle .

5. INSTRUMENTATION
 Main parts of Ir spectrometer
1) Ir radiation source :eg incandensecent lamp, nernst
glower, globar source, mercury arch
2) Monochrometer- it select the desired frequencies
from radiation source and reject the radiation of
other frequencies eg: prism and grating
monochrometer
3) Sample cells
4) Detectors-balometer, thermocouple, golay cell etc

6. CONTD…

7. APPLICATION OF IR SPECTROSCOPY
To organic compound:
1. Identification of substaance - some characterstic ir
absorption region

8. CONTD…
For example: ir spectra of citral

9. CONTD..
 Ir spectra of methanol

10. CONTD..
2. Determination of molrecula structure
3. Detection of impurities
4. In identification of isomerism
To inorganic compound
It is dificulte task to carryout spectrum analysis of
complexes even if their structure is known
The main reason for this is following
1. High modes of vibration
2. Low symmetry of complexes
3. Chelate formation

11. REFERENCE
 Instrumental method of chemical analysis by G. R.
Chatwal
 https://en.wikipedia.org/wiki/Infrared_spectroscopy
 https://www.google.co.in/search?rlz=1C1CHBD_enIN765IN766&
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 https://www.google.co.in/search?rlz=1C1CHBD_enIN765IN76
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