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Sect. 11.12: The carbonyl stretching region

Sect. 11.12: The carbonyl stretching region. This region stretches from about 1800 to 1650 cm -1 The base value is 1715 cm -1 (ketone) The bands are very strong!!!. WWU Chemistry. 2-Butanone. sp 3 C-H stretch. C=O stretch. WWU Chemistry. Nonanal. aldehyde C-H (pair). C=O stretch.

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Sect. 11.12: The carbonyl stretching region

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  1. Sect. 11.12: The carbonyl stretching region • This region stretches from about 1800 to 1650 cm-1 • The base value is 1715 cm-1 (ketone) • The bands are very strong!!! WWU Chemistry

  2. 2-Butanone sp3 C-H stretch C=O stretch WWU Chemistry

  3. Nonanal aldehyde C-H (pair) C=O stretch sp3 C-H stretch WWU Chemistry

  4. Normal Base Values for C=O Stretching WWU Chemistry

  5. Dodecanoyl Chloride C=O stretch sp3 C-H WWU Chemistry

  6. Ethyl Butanoate C-O stretch sp3 C-H C=O stretch WWU Chemistry

  7. Butanoic Acid O-H stretch C=O stretch WWU Chemistry

  8. Propanamide sp3 C-H C=O and N-H stretch (pair) N-H bend WWU Chemistry

  9. Conjugation of C=O with C=C • Conjugation of a carbonyl with a C=C bond shifts values to lower frequencies • For aldehydes, ketones and esters, subtract about 30 cm-1 for conjugation with C=O • Conjugated ketone = 1690 to 1680 cm-1 • Conjugated ester = 1710 to 1700 cm-1 • C=C becomes quite strong!! WWU Chemistry

  10. 4-Methyl-3-penten-2-one C-H stretch C=O stretch C=C stretch WWU Chemistry

  11. Acetophenone C-H stretch aromatic C=C conj C=O WWU Chemistry

  12. Cyclic Ketones (C=O Stretch) WWU Chemistry

  13. Cyclopentanone C-H stretch strained ring C=O WWU Chemistry

  14. Sect. 11.13: C=C stretching region • C=C double bond at 1650 cm-1 is often weak or not even seen. • C=C benzene ring shows peak(s) at 1600 and 1450 cm-1 , one or two at each value. WWU Chemistry

  15. 1-Hexene sp2 C-H C=C stretch out of plane bendings (oops) sp3 C-H stretch WWU Chemistry

  16. Toluene sp2 C-H sp3 C-H aromatic C=C aromatic oops WWU Chemistry

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