Chapter 13

Chapter 13 - Chapter 13- Spectroscopy I. Types a. Nuclear...

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Chapter 13- Spectroscopy I. Types a. Nuclear Magnetic Resonance (NMR)- tells about C skeleton and the environment of the Hs attached to it b. Infrared Specrtoscopy (IR)- presence or absence of key functional groups II. Principles of Molecular Sectroscopy- electromagnetic radiation a. Electromagnetic Radiation i.Properties of waves and particles ii. Photon - particles of electromagnetic radiation which possesses an amount of energy called a quantum b. Plank i.E=hv 1. E- energy of a photon 2. h- planks constant 6.63x10 -34 J.s 3. v- frequency (s -1 ) c. Electromagnetic spectrum- range of photon energies i.Frequency is inversely proportional to wavelength ( greater the frequency, shorter the wavelength ) ii.Energy is directly proportional to frequency (electromagnetic radiation of higher frequency has more energy than radiation of lower frequency iii.Spectrum- wavelength increases going down and frequency increases going up 1. Gamma Ray 2. X-ray 3. UV 4. Visible 5. Infrared 6. Microwave 7. Radiowave iv.When a molecule is exposed to electromagnetic radiation it may absorb a photon, increasing its energy by an amount equal to the energy of the photon. Molecules are selective with the frequencies that they absorb depending on the molecular structure. III. Quantized energy states a. In order for a molecule to absorb a photon the energy of the photon must equal the energy difference between two states (nuclear spin states, vibrational states, electronic states) b. Resonance - the transfer of energy between two objects that occurs when their frequencies are matched.
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c. Each type i.NMR- photon must equal difference in energies of two different spin states of an atomic nucleus. ii.IR- photon must equal difference in energies of two different vibrational energy states iii.UV-VIS- photon must equal difference in energies of two different electronic energy states d. Quantized- more of the molecules exist in the lower energy state E 1 than in the higher energy state E 2 . e. To raise a molecule from a lower state to a higher state requires the addition of an increment of energy equal to E. Thus, when electromagnetic radiation is incident upon a molecule, only the frequency whose corresponding energy equals E is absorbed. All other frequencies are transmitted. f. Sectrometer- measures the absorption of electromagnetic radiation by a sample. When frequency of the radiation emitted from the spectrometer is reached at which the sample absorbs the radiation, the decrease in intensity of radiation detected decreases. g. The relation between frequency and absorption is plotted
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This note was uploaded on 06/29/2008 for the course CHM 2212 taught by Professor Mcquade during the Spring '08 term at FSU.

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Chapter 13 - Chapter 13- Spectroscopy I. Types a. Nuclear...

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