10.5 Spectroscopy and the Electromagnetic
Spectrum
The electromagnetic spectrum covers a continuous range of wavelengths
and frequencies, from radio waves at the low-frequency end to gamma
(g) rays at the high-frequency end
10.6 Infrared Spectroscopy
Infrared (IR) region
• Ranges from 7.8 x 10-7 m to 10-4 m
•
2.5 x 10-6 m to 2.5 x 10-5 m used by organic chemists
• Wavelengths given in micrometers (1 mm = 10-6 m)
• Frequencies given in wavenumbers
• Wavenumber
• Reciprocal of wavelength in centimeters
• Expressed in units of cm-1
Infrared Spectroscopy
Molecules stretch or bend at specific frequencies
• Energy is absorbed if the frequency of the radiation
matches the frequency of the vibration
IR spectrum → What molecular motions? → What functional
groups?
10.7 Interpreting Infrared Spectra
Most functional groups have characteristic IR absorption
bands that don’t change from one compound to another
Interpreting Infrared Spectra
Fig. 13-5, p. 509
Fig. 13-6, p. 510
Fig. 13-7, p. 510
Fig. 13-9, p. 512
Fig. 13-10, p. 513
Fig. 13-11, p. 513
Fig. 13-12, p. 514
Fig. 13-13, p. 515
Table 13-2, p. 522
Fig. 13-8, p. 511
Fig. 13-15, p. 523
Fig. 13-18, p. 526
Fig. 13-19, p. 527
Fig. 13-20, p. 528
Infrared Spectra of Some Common Functional
Groups
Characteristic aldehyde and ketone IR absorptions
Infrared Spectra of Some Common Functional
Groups
Characteristic ester IR absorptions
Fig. 13-22, p. 529