KARNATAKA COLLEGE OF PHARMACY

T . SrinivasAssistant

professor Pharmaceutical Analysis

Department : -

Presentation By :-Vijay Kumar1st M Pharmacy

Pharmaceut ica l Technology

IR

SpectroscopyPrinciple

SPECTROSCOPY….. ? Spectroscopy means it is a method of

seeing unseen able EMR (electro magnetic radiation)

Using electromagnetic radiation to obtain information about molecule and atoms its too small to see

Energy of an EMR given by the equation :

E =hv E = energy of radiationh = plank’s constant V = frequency of radiation

EMR Analytical medium

Conc.should be low

Spectrophotograph

Excitation electron – uv

Vibration changes in electron - IR

Spine rotational frequency –NMR (Radio frequency)

1. Based on the atomic or molecular level

2.Based on the absorption or emission levels

3.Based on electronic or magnetic levels

Atomic spectroscopy :- The energy change takes place at atomic level

Molecular level :- The energy change takes place at molecular level

Types of Spectroscopy

Based on atomic or molecular level

Based on Absorption or emission levelAbsorption spectroscopy :- Absorption radiation

studied in uv ,IR ,NMR , Colorimetry spectroscopy

Emission Spectroscopy :- emission radiation studied in Flame photometry ,Fluorimetry

Based on electronic or magnetic level Electronic Spectroscopy :- uv , colorimetric only study EMR without any magnetic field

Magnetic Spectroscopy :-NMR spectroscopy ,Study the EMR with under the influence of magnetic field

Introduction Energy of molecule = Electronic energy

+ vibrational energy + Rotational energy

Concerned with the study of infrared rays . Causes the vibrational transition in the molecule

Thus known as the vibrational spectroscopy

IR its structural elucidation (Structurally make clear) forming depending up on the functional group and bonds present in chemical substance

IR spectroscopy

0.8 2.5 15

20

12500 4000 667 50 CM

Range of infrared RegionWAVE LENGTH

WAVE NUMBERThe region may be divided in to 4 section1) The Photo graphic region :- visible range 1.0 to 1.2 micron2)The very near infrared region :- overtone region and its range from 1.2 to 2.5 micron3)Near infrared region :- vibration rotation region and range from 2.5 to 25 micron4) Far – infrared region :- rotation region and range from 25 to 300-400

(a) Group frequency region (b) Finger print region

In these region wavelength range from 2.5 to 8.0

Wave number from 4000 -1300cm-1 Here stretching and bending vibrational

bands are associated with specific structural or functional groups observed frequently

Stretching frequency are found in group frequency region

Another regions in infrared spectrum are

(a) Group frequency region

Sl . no Molecule Frequency (cm-1)

C-H stretch1. CHCl3 30192. CH=CH 3287C=o stretch1. CH3COCH3 17152. CF3COOH 1776

Finger print regionThe region wavelength ranging from 8.0 – 2.5 micron and a wave number from 1300 – 4000 cm-1 . Here the vibrational modes depends solely and strongly on the rest of the molecule.Ex :-The c-c stretching frequency depends largely on bonding of the carbon atoms

In any molecule. It is known that atoms or groups of atoms are connected by bonds

The bonds maintain some vibrations, with some frequency, characteristic to energy portion of the molecule this called natural frequency of vibration

When energy in the form of IR is applied IR frequency is equal to Natural frequency of vibration,

Absorption of IR radiation takes place and a peak is observed

Principle of IR

IR of Ethanol(CH3CH2OH)

c c o

H H H

HH

C-H stretching2850-2960 cm-1

C-H bending 1340 cm-1 C-O stretching

1250 -1350 cm-1

O-H stretching 3590-3650 cm-1O-H bending 1050-1150 cm-1

Every bond or portion of molecules or functional group requires different frequency

for absorption. Characteristic peak is observed for

functional group or part of molecule In other words , IR spectra is nothing but

a finger print of a molecule E.g. IR spectra of Ibuprofen

1. Change in dipole moment :- when molecule only absorb IR radiation ,its causes changes in it’s electric dipole

A molecule is said to have electric dipole when there is a slight positive and a

negative charge on its compound

Applied IR frequency = Natural frequency

Of radiation .Other wise compound do not give IR peak

Types of vibrations 1. Stretching 2. Bending vibrations

Criteria for a compound to absorb IR radiation

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