Spectroscopy Learning Module, Part 2

Spectroscopy Learning Module, Part 2 - When a molecule is...

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Unformatted text preview: When a molecule is exposed to infrared light, the bonds in the molecule begin to vibrate. The infrared region of the electromagnetic spectrum is just below red in the visible region. Wavelengths are usually 2.5-25 m. More common units are wavenumbers, or cm-1 , the reciprocal of the wavelength in centimeters. Wavenumbers are proportional to frequency and energy. 1 ovalent bonds vibrate at only certain Covalent bonds vibrate at only certain allowable frequencies, depending on the strength of the bond and the atoms connected by that bond. You can think of the bond like a spring. 2 This is great, because it will allow us to see unique signals for different types of bonds. 3 Molecules have various vibrational modes. Most common are stretching and bending. 4 Since energy is quantized, different kinds of bonds absorb light of different frequencies. No two molecules will give exactly the same IR spectrum (except enantiomers). Simple stretching region: 1600-3500 cm-1 . Complex vibrations occur from 600-1500 cm-1 , and we call this region the the fingerprint region of the spectrum....
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This note was uploaded on 07/14/2011 for the course CHM 2211L taught by Professor Davidson during the Summer '08 term at University of Florida.

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Spectroscopy Learning Module, Part 2 - When a molecule is...

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