Organic Chemistry, 5th Edition L.G. Wade jr Chapter 12 Infrared Spectroscopy and Mass Spectrometry Jo blackburn Richland college, dallas TX Dallas County Community College District c 2003. Prentice hall
Chapter 12 Infrared Spectroscopy and Mass Spectrometry Jo Blackburn Richland College, Dallas, TX Dallas County Community College District © 2003, Prentice Hall Organic Chemistry, 5th Edition L. G. Wade, Jr
ntroduction Spectroscopy is an analytical technique which helps determine structure It destroys little or no sample The amount of light absorbed by the sample is measured as wavelength is varied Chapter 12 2
Chapter 12 2 Introduction • Spectroscopy is an analytical technique which helps determine structure. • It destroys little or no sample. • The amount of light absorbed by the sample is measured as wavelength is varied. =>
Types of Spectroscopy Infrared (IR) spectroscopy measures the bond vibration frequencies in a molecule and is used to determine the functional group Mass spectrometry(MS) fragments the molecule and measures the masses Nuclear magnetic resonance(NMR) spectroscopy detects signals from hydrogen atoms and can be used to distinguish isomers Uitraviolet (UV spectroscopy uses electron transitions to determine bonding patterns. => Chapter 12
Chapter 12 3 Types of Spectroscopy • Infrared (IR) spectroscopy measures the bond vibration frequencies in a molecule and is used to determine the functional group. • Mass spectrometry (MS) fragments the molecule and measures the masses. • Nuclear magnetic resonance (NMR) spectroscopy detects signals from hydrogen atoms and can be used to distinguish isomers. • Ultraviolet (UV) spectroscopy uses electron transitions to determine bonding patterns. =>
Electromagnetic Spectrum EXamples: X rays, microwaves, radio waves,visible light, IR, and UV Frequency and wavelength are inversely proportional C=nv, where c is the speed of light Energy per photon= hv, where h is Plancks constant Chapter 12
Chapter 12 4 Electromagnetic Spectrum • Examples: X rays, microwaves, radio waves, visible light, IR, and UV. • Frequency and wavelength are inversely proportional. • c = ln, where c is the speed of light. • Energy per photon = hn, where h is Planck’s constant. =>
The Spectrum and Molecular Effects Wavelength(n) Energy Molecular effects higher frequenc m kcal/mol shorter wavelength 10-9 gamma rays 10 10 rays onization vacuum UV 10 near UV electronic transitions 10-4 visible infrared 10-3 molecular vibrations (R) 10 10 microwave 10 4 rotational motion lower frequency radio 10-6 nuclear spin transitions longer wavelength
Chapter 12 5 The Spectrum and Molecular Effects => =>