INFRARED SPECTROSCOPY

INFRARED SPECTROSCOPY
Infrared radiation stimulates molecular vibrations.
Infrared spectra are traditionally displayed as %T (percent transmittance) versus wave number.
Useful in identifying presence or absence of functional groups.

¨IR range- 10cm- - 12800cm-

¨Sub regions
¨Near IR – 12500 – 4000cm-
¨Middle IR – 4000 – 667cm-
¨Far IR – 667 – 50 cm-
Finger print region – 900 – 1400cm- (identify the compound)

Water is a
-bent- non linear – triatomic molecule
Formula used for finding vibrations in non-linear molecule – (3N-6)
Carbon-di-oxide is a
– Linear – triatomic molecule
Formula used for finding vibrations in non-linear molecule - (3N-5)