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Questions of the day:

Questions of the day:. Which absorptions on an IR spectrum would show you that your unknown is probably a ketone or aldehyde? b) that your unknown is probably a carboxylic acid?. Today: Inert compounds IR; UV Next time: Mass spectrometry. “Inert Compounds”. Alkanes Aromatic Hydrocarbons

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Questions of the day:

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  1. Questions of the day: • Which absorptions on an IR spectrum would show you • that your unknown is probably a ketone or aldehyde? • b) that your unknown is probably a carboxylic acid?

  2. Today: • Inert compounds • IR; UV • Next time: • Mass spectrometry

  3. “Inert Compounds” Alkanes Aromatic Hydrocarbons (Alkyl halides. Aryl halides.)

  4. Spectroscopy http://www.chem.ucla.edu/~webspectra/index.html • Infrared Spectroscopy (IR) • IR region = 4000 - 400 cm-1(cm-1 unit is the wave number scale and is given by 1/wavelength in cm) E= h n • What information do we get from an IR spectrum? • What is the cause for the typical absorptions?

  5. Fingerprint region butyl acetate

  6. http://www.chem.ucla.edu/~webspectra/index.html

  7. http://www.chem.ucla.edu/~webspectra/index.html

  8. Aromatics aromatic overtones

  9. http://www.chem.ucla.edu/~webspectra/index.html

  10. http://www.chem.ucla.edu/~webspectra/index.html

  11. Alcohols Gas phase!

  12. Phenol

  13. Ketones

  14. Carboxylic Acids

  15. UV/Visible Spectrophotometry Which compounds generally absorb in the UV? CH4? CH3(CH2)10CH3? Ethanol? Benzene? Naphtalene? -Carotene? FeCl3? Which compounds absorb in the visible range? CH4? CH3(CH2)10CH3? Ethanol? Benzene? Naphtalene? -Carotene? FeCl3? • See Chapter in your Lecture text (conjugated systems) • to p* HOMO to LUMO A = e x C x l A = absorbance; e = molar absorptivity C = concentration in mol/L; l = sample pathlength in cm

  16. UV/Visible Spectrophotometry

  17. lmax

  18. Next time: • Mass Spectrometry • MiniQuiz on today’s class

  19. OH O N NO NH 2 2 2 + NO 2 MiniQuiz 8 Problem: Complete this reaction equation:

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