1 / 29

13.20 Introduction to Infrared Spectroscopy

13.20 Introduction to Infrared Spectroscopy. Gives information about the functional groups in a molecule. Infrared Spectroscopy. region of infrared that is most useful lies between 2.5-16  m (4000-625 cm -1 ) depends on transitions between vibrational energy states stretching bending.

wells
Download Presentation

13.20 Introduction to Infrared Spectroscopy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 13.20Introduction to Infrared Spectroscopy Gives information about the functional groups in a molecule

  2. Infrared Spectroscopy region of infrared that is most useful lies between2.5-16 m (4000-625 cm-1) depends on transitions between vibrational energy states stretching bending

  3. Stretching Vibrations of a CH2 Group Symmetric Antisymmetric

  4. Bending Vibrations of a CH2 Group In plane In plane

  5. Bending Vibrations of a CH2 Group Out of plane Out of plane

  6. 13.21Infrared Spectroscopy

  7. Infrared Spectroscopy Characteristic functional groups usually found between 4000-1600 cm-1. From 1300-625 cm-1 called fingerprint region. Insert Figure 13.30 here

  8. 13.22Characteristic Absorption Frequencies

  9. Table 13.4 Infrared Absorption Frequencies Structural unit Frequency, cm-1 Stretching vibrations (single bonds) sp C—H 3310-3320 sp2 C—H 3000-3100 sp3 C—H 2850-2950 sp2 C—O 1200 sp3 C—O 1025-1200 Note relationship between, hybridization bond strength and absorption frequency

  10. Page 550 Infrared “active” vibrations must change the dipole moment of the vibrating or bending group. Infrared absorption intensities are proportiional to the polarity of the functional group.

  11. C C —C C— —C N Note relationship between hybridization bond strength, bond order and absorption frequency Structural unit Frequency, cm-1 Stretching vibrations (multiple bonds) 1620-1680 2100-2200 2240-2280

  12. C O Table 13.4 Infrared Absorption Frequencies Structural unit Frequency, cm-1 Stretching vibrations (carbonyl groups) Aldehydes and ketones 1710-1750 Carboxylic acids 1700-1725 Acid anhydrides 1800-1850 and 1740-1790 Esters 1730-1750 Amides 1680-1700

  13. RCH CH2 R2C CH2 cis-RCH CHR' trans-RCH CHR' R2C CHR' Table 13.4 Infrared Absorption Frequencies Structural unit Frequency, cm-1 Bending vibrations of alkenes 910-990 890 665-730 960-980 790-840

  14. Structural unit Frequency, cm-1 Bending vibrations of derivatives of benzene Monosubstituted 730-770 and 690-710 Ortho-disubstituted 735-770 Meta-disubstituted 750-810 and 680-730 Para-disubstituted 790-840 Also note the characteristic “overtone” vibrations between 1650-2000 cm-1 that identify substituted Benzenes. (p 240, Fig. 11.8, Williamson)

  15. Table 13.4 Infrared Absorption Frequencies Structural unit Frequency, cm-1 Stretching vibrations (single bonds) O—H (alcohols) 3200-3600 O—H (carboxylic acids) 3000-3100 N—H 3350-3500

  16. Fig. 13.31.a

  17. Fig. 13.31.b

  18. Fig. 13.31.c

  19. Fig. 13.31.d

  20. Fig. 13.32.a

  21. Fig. 13.32.b

  22. Fig. 13.32.c

  23. Fig. 13.32.d

  24. Fig. 13.32.e

  25. Fig. 13.32.f

  26. Fig. 13.32.g

  27. Fig. 13.32.h

  28. Fig. 13.33

More Related