Scene 1

Engineering chemistry  UNIT 5: Spectroscopic Techniques  Topic : IR-Spectroscopy

Suman S. Kahandal K.K.Wagh Institute Of Engineering Education ,Nasik

Scene 2

TYPES OF
SPECTROSCOPY
 UV- Vis spectroscopy uses electronic transitions to
determine bonding patterns
 Infrared (IR) spe...

Scene 3

EMR ANALYTE SPECTROPHOTOGRAPH
1.UV-Visible radiations--excitation of electronsUV-visible spectrum
2.IR-radi...

Scene 4

Scene 5

THE ELECTROMAGNETIC
SPECTRUM
3
IR REGIONS RANGE
Near infrared region 0.8-2.5 µ (12,500 - 4000 cm-1)
Mid infrared region 2....

Scene 6

1)Correct frequency of radiation :   a molecule absorbs radiation only when natural frequency of vibration is same as the frequency of incident radiation  2) Dipole moment :  The second condition to absorb IR radiation .a molecule can only absorb IR radiation when its absorption causes changes   in dipole moment .only those vibration which result change in dipole moment are IR active . ( symmetrical molecule like H2 ,Cl2,O2 do not have dipole moment ,they are IR inactive ,while  Hcl  is IR active .)  If  above condition  are  not  met,  no   absorption can   occur. S O ,  NO T  A L   L b o nds 	 i n  a   molecule   are  capable of absorbing IR-  energy.

Conditions of absorption of IR radiation  ( Requirements of IR radiation ) :

Scene 7

Change in internuclear distance  stretching

Scene 8

1) Symmetrical stretching vibration:        involves movement of atom with respect to particular atom in the         same direction

stretching vibration  (change in  internuclear  distance)

2) Asymmetrical stretching vibration:   involves movement of atom with respect to particular atom in the same plane but not in the direction

Scene 9

1)Scissoring  :movement of two atom in opposite direction, but in same plane

Bending Vibration  (change in bond angles )

2) Rocking :  movement of atoms in the same plane in same direction

Scene 10

1) Wagging :  movement of atom up the plane below the plane, but out of plane  4) Twisting  : movement of one atom up or one atom down ,but out of plane  Out-of-plane twisting

Scene 11

CLASSIFICATION OF IR BANDS
Three types : strong (s), medium (m), or weak (w)
Depending on their relative intensities in th...

Scene 12

DETECTION OF IMPURITIESDETECTION OF IMPURITIES
 Determined by comparing sample spectrum with
the spectrum of pure referen...

Scene 13

Amide A (about 3500 cm-1
) is with more than 95% due to the N-H stretching
vibration
Amide I (between 1600 and 1700 cm-1
)...

Engineering chemistry UNIT 5: Spectroscopic Techniques Topic : IR-Spectroscopy

Page 1 (0s)

Page 2 (55s)

Page 3 (2m 1s)

Page 4 (3m 3s)

Page 5 (3m 17s)

Page 6 (3m 59s)

Page 7 (5m 31s)

Page 8 (6m 19s)

Page 9 (7m 5s)

Page 10 (8m 10s)

Page 11 (9m 7s)

Page 12 (9m 47s)

Page 13 (10m 36s)

Page 14 (10m 56s)

Page 15 (11m 35s)