1. QUÍMICA ORGÂNICA III – UFPI/2009:2 Infravermelho: Revisão Prof. Dr. Sidney Lima

2. The Spectrum and Molecular Effects =>

3. Stretching Frequencies Frequency decreases with increasing atomic weight. Frequency decreases with increasing atomic weight. Frequency increases with increasing bond energy. => Frequency increases with increasing bond energy. =>

4. An Infrared Spectrometer =>

5. FT-IR Spectrometer Uses an interferometer. Uses an interferometer. Has better sensitivity. Has better sensitivity. Less energy is needed from source. Less energy is needed from source. Completes a scan in 1-2 seconds. Completes a scan in 1-2 seconds. Takes several scans and averages them. Takes several scans and averages them. Has a laser beam that keeps the instrument accurately calibrated. => Has a laser beam that keeps the instrument accurately calibrated. =>

6. An Alkane IR Spectrum =>

7. An Alkyne IR Spectrum =>

8. An Alcohol IR Spectrum =>

9. An Amine IR Spectrum =>

10. A Ketone IR Spectrum =>

11. An Aldehyde IR Spectrum =>

12. O-H Stretch of a Carboxylic Acid =>

13. An Amide IR Spectrum =>

14. A Nitrile IR Spectrum =>

15. Summary of IR Absorptions =>

16. Strengths and Limitations IR alone cannot determine a structure. IR alone cannot determine a structure. Some signals may be ambiguous. Some signals may be ambiguous. The functional group is usually indicated. The functional group is usually indicated. The absence of a signal is definite proof that the functional group is absent. The absence of a signal is definite proof that the functional group is absent. Correspondence with a known sample’s IR spectrum confirms the identity of the compound. => Correspondence with a known sample’s IR spectrum confirms the identity of the compound. => Adapted by Organic Chemistry, 5 th Edition L. G. Wade, Jr.