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2) Infra-red spectroscopy

2) Infra-red spectroscopy. The Energy of molecular vibrations. To be IR active, a molecule must undergo a change in dipole. IR spec. E=hf (E=h  ) Meaning the electromagnetic spectrum covers ALL energy ranges. http://www.wag.caltech.edu/home/jang/genchem/infrared.htm. IR spec.

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2) Infra-red spectroscopy

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  1. 2) Infra-red spectroscopy The Energy of molecular vibrations. To be IR active, a molecule must undergo a change in dipole.

  2. IR spec • E=hf (E=h) Meaning the electromagnetic spectrum covers ALL energy ranges.

  3. http://www.wag.caltech.edu/home/jang/genchem/infrared.htm

  4. IR spec ……Zooming in on the IR range… the energy of molecular bends and stretches

  5. IR spec NOT ON SYLLABUS: • What’s a degree of freedom? A way in which molecule can undergo a vibration (bend or stretch)

  6. I.R. – degrees of freedom • E.g. CO2 (a linear molecule) • n=3 (the number of atoms) • 3n-5 = 4 “modes” of vibration

  7. IR spec Vibrations (bends and stretches) of CO2

  8. IR spec

  9. IR spec

  10. IR spec • Can also bend in and out of the plane of the paper. This is the second way of bending

  11. IR spectrum of CO2 3n-5 (linear) = 4 science.widener.edu/svb/ftir/ir_co2.html

  12. IR spec • CHART of IR absorbancies • Various IR

  13. IR spec

  14. IR spec A sample IR spectrum of octane (nujol)

  15. IR spec Alkanes , Alkenes, Alcohols Halogen, Aldehydes, Ketones, Esters, Carboxylic acids, Aromatics, Amines. Chemguides: propan-1-ol, (2-ol next page) D:\Users\user\Documents\--- A-Level and Science\Mike

  16. IR spec

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