IR Infrared Spectroscopy Identify the functional group(s)

Electromagnetic Spectrum

Bond Vibrations Energy absorption radiation Amplitude

Stretching Bending

Classical IR Spectrometer

NaCl 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 cm-1 Bond C-H Alkanes 2850-2960 C-H Alkenes 3020-3080 C-H Arenes 3000-3100 C-O Alcohols, ethers 1080-1300 C=O Aldehydes, ketones... 1690-1760 O-H Alcohols 3200-3600 Acids 2500-3000 N-H Amines 3300-3500

Alcohol -OH C-H -O-R

PrimaryAmine -NH2

Secondary Amine N-H

Ketone C=O

Aldehyde RCO-H C=O

Carboxylic Acid OH C=O

Ester C-O C=O

Functional Group? Carbonyl group -- Ketone

Functional Group? Alcohol

Functional Group? Carboxylic Acid

Functional Group? Ester

Functional Group? amine (secondary)

C8H8O C6H5COCH3

C3H8O isopropyl alcohol

C4H8O2 CH3COOCH2CH3

C5H10O CH3COCH2CH2CH3