E = hhc

=

Electromagnetic Spectrum

5.7 X 105 9.5 X 103

1.7 X 103

4.8 X 102 9.5 X 10-31.272 10-4

Electromagnetic Spectrum

(Kcal/mol)

E = hhc

=

Pi and non-bondingelectrons

Electromagnetic Spectrum

Proton SpinMolecularRotation

MolecularVibration and rotationnucleus

valenceelectrons

Pi and non-bondingelectrons

Electromagnetic Spectrum

Proton SpinMolecularRotation

MolecularVibration and rotationnucleus

NMRMicrowaveInfraredUltraviolet - Visible

Mass Spectrometry

X-ray diffractometry

valenceelectrons

Infrared Spectroscopy

To here!From here…

Functional Groups: √ OH× C=O× C=C√ C-O

Infrared (IR) Spectroscopy gives informationon the functional groups within molecules

Infrared Spectroscopy

Typical stretching vibrations of a methylene group

12a–8

Different kinds of bending vibrations for a methylene

group

Rocking Wagging Twisting

                

                

                

Symmetricalstretching

Antisymmetricalstretching

Scissoring

                                 

                

Schematic diagram of a typical infrared spectrophotometer

Fourier Transform

Spectrometer,Interferogramand Spectrum

Factors affecting IR Stretch Frequency

• Masses of atoms at ends of a bond• Springs connecting small weights vibrate faster

than springs with large weights.• H-C > C-C• H-O > C-O

• Type of bond (force constant)• Shorter, stronger springs vibrate faster than long,

weak springs• C≡C > C=C > C-C

Hookes’ Law

m2m1

Fig. 10.15, p. 383

A Good Guide

Low EnergyHigh Energy

E = hhc

=

Infrared spectra of 1-hexyne & 1-hexene

Infrared spectra of 1-hexene & 1-hexanol

Infrared spectra of butanal and 2-butanone

A Closer Look at Carbonyl Compounds

A Closer Look at Carbonyl Compounds

A Closer Look at Carbonyl Compounds