Chemistry 2213A/B Final: Chem 2213 - Topic 8 Final Notes
31 Jan 2018
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Oscillating waves of electric and magnetic fields. Travels at the speed of light (c) We observe low energy nuclear transitions in spectroscopy: low energy em does not affect molecular structure, micro causes rotation. Ir causes bond vibration: mid-high energy em affects structure and is no good for spectroscopy, visible/uv electronic transitions, x-ray/gamma ejects electrons. Emr can behave as a wave or as particles (photons) The energy of a photon is: e = hv = hc/ : therefore v is inversely proportional to . Photons are absorbed by molecules to increase their energy state: results in transition. We pass all wavelengths of ir through a molecule and determine which ones were absorbed. Two main regions: (split graph at 1500) Spectra ranges from 4000 to 400 cm-1 (wavenumbers (cm-1) = 1/ : functional group region: 1500+ (more useful because there are a lot less signals, fingerprint region: 400-1500. Higher energy ir on left, low energy ir on right.
