Infrared Spectroscopy

Electromagnetic radiation Ultraviolet –190 nm to 400 nm –Electronic transitions  to  *  to  * Visible –400 nm to 700 nm –Electronic transitions involving molecular orbitals

Electromagnetic Radiation Infrared –800 nm to 2500 nm Near infrared –2500 nm (4000 cm -1 ) to nm (667 cm -1 ) Ordinary infrared –15000 nm to nm Far infrared

Energy and vibrations Energy is measured in cm-1 –4000 cm -1 is the high energy end and 667 cm -1 is the low energy end. Vibrations –Stretching (require higher energy) –Bending (normally involve several bonds) –C=C at higher energy than C-C

Nonane C-H stretch and C-H bends C-H stretch, sp 3 CH 2 bend CH 3 bend

1-Octene C-H stretch, C=C stretch, CH bend sp 2 CH str sp 3 CH str C=C str CH bends

1-Octyne CH stretch, C≡C stretch sp CH str C≡C str CO 2

m-Xylene Aromatic peaks CH > ,1500

Phenanthrene Aromatic peaks CH > 3000 and cm -1

1-Pentanol OH stretch, CH stretch, CH bend, CO stretch C-O str,

2-Butanol OH stretch, CH stretch, CH bend, CO stretch

4-Methyl-2-pentanone CH stretch, C=O stretch C=O str

4-Methylacetophenone CH stretch, C=O stretch C=O < 1700, conjugated

Pentanal CH and CHO stretches, C=O stretch Water C=O stretch

Benzaldehyde CH and CHO stretches, C=O stretch, aromatic peaks C=O str < 1700 CHO stretches

Hexanoic acid OH stretch and C=O stretch C=O str OH stretch

Ethyl benzoate CH stretch, C=O and C-O stretches C=O str, 1725 cm -1 C-O stretch

Isobutyl amine NH stretch, NH bend

Diisopropyl amine NH stretch, NH bend

Methyl formamide NH stretch, C=O stretch

Benzonitrile CN stretch Aromatic C≡N stretch

Nitrobenzene NO stretches (asymmetric and symmetric) NO stretch

The Nicolet Infrared