111 CHEM 344 Organic Chemistry Lab June 18 th 2008 Spectroscopy of Organic Compounds Lecture 3 –Infrared and Mass Spec Nick Hill

cm -1

1716 cm cm -1

2260 cm -1

Molecular Fragments Molecule Molecular Ion EI

Mass Spectrum of methanol CH 3 OH [CH 2 OH] + [CHO] + [CH 3 ] + [CH 3 OH] +.

Cation stability more important than radical stability Molecular Ion A + B CationRadical X X A + B CationRadical

C 6 H 13 + C 5 H 11 + C4H9+C4H9+ C3H7+C3H7+ C2H5+C2H5+ Mass Spectrum of octane

Mass Spectrum of 2,2,4-trimethylpentane 57 43

Mass Spectrum of 1-butanol via loss of H 2 O Resonance stabilized

Mass Spectrum of 2-methyl-2-butanol

Mass Spectrum of 2-octanone via  - cleavage

m/z = 43 m/z = 113 Molecular ion m/z = 128  -cleavage at a C=O group

Mass Spectrum of 2-octanone via  - cleavage McLafferty rearragement

McLafferty rearrangement of a ketone 1-pentene McLafferty rearrangement of a carboxylic acid ethene

Mass Spectrum of Benzamide

19 Mass Spectrum of Toluene Loss of H Benzyl cation???

Tropylium cation m/z = 91 Toluene radical cation m/z = 92 m/z = 91 common to all alkyl benzenes

Mass Spectrum of 3-methyl-1-butanamine 30 via  - cleavage