Infrared SpectroscopyIR

Identify the functional group(s)

Electromagnetic Spectrum

Energy

Amplitude

absorption radiation

Bond Vibrations

CH

H

CH

HBending

CH

H

CH

HStretching

Classical IR Spectrometer

NaCl IR PlatesNaCl IR Plates

A drop of sample is place between the NaCl plates

NaCl cell for solutions

Wavenumber cm-1

E = h= hc/

Characteristic IR Absorption Frequencies

C-H Alkanes 2850-2960C-H Alkenes 3020-3080C-H Arenes 3000-3100

C-O Alcohols, ethers 1080-1300

C=O Aldehydes, ketones... 1690-1760

O-H Alcohols 3200-3600Acids 2500-3000

N-H Amines 3300-3500

cm-1Bond

-OH

C-H

-O-R

Alcohol

PrimaryAmine

-NH2

Secondary Amine

N-H

Ketone

C=O

Aldehyde

C=O

RCO-H

Carboxylic Acid

OH

C=O

Ester

C=OC-O

Carbonyl group -- Ketone

Functional Group?

Alcohol

Functional Group?

Carboxylic Acid

Functional Group?

Ester

Functional Group?

amine (secondary)

Functional Group?

C6H5COCH3

C8H8O

isopropyl alcohol

C3H8O

CH3COOCH2CH3

C4H8O2

CH3COCH2CH2CH3

C5H10O