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

2. region of infrared that is most useful lies between 2.5-16  m (4000-625 cm -1 ) depends on transitions between vibrational energy states stretchingbending Infrared Spectroscopy

3. Stretching Vibrations of a CH 2 Group SymmetricAntisymmetric

4. Bending Vibrations of a CH 2 Group In plane

5. Bending Vibrations of a CH 2 Group Out of plane

6. Example of infrared spectrum Hexane Transmittance (%) 100 0 Wave number, cm -1 440036002800200016001200800 C—H stretching bending bending bending

7. Example of infrared spectrum Hexane Transmittance (%) 100 0 Wave number, cm -1 440036002800200016001200800 no peaks higher than 3000 cm -1

8. Infrared spectrum of 1-hexene Transmittance (%) 100 0 Wave number, cm -1 440036002800200016001200800 peak higher than 3000 cm -1 C=C—H C=C CH 2 =C—

9. Structural unitFrequency, cm -1 Stretching vibrations (single bonds) sp C—H3310-3320 sp 2 C—H3000-3100 sp 3 C—H2850-2950 sp 2 C—O1200 sp 3 C—O1025-1200 Table 13.4 (p 519) Infrared Absorption Frequencies

10. Structural unitFrequency, cm -1 Stretching vibrations (multiple bonds) Table 13.4 (p 519) Infrared Absorption Frequencies C C 1620-1680—CN —CC— 2100-2200 2240-2280

11. Structural unitFrequency, cm -1 Stretching vibrations (carbonyl groups) Aldehydes and ketones1710-1750 Carboxylic acids1700-1725 Acid anhydrides1800-1850 and 1740-1790 Esters1730-1750 Amides1680-1700 Table 13.4 (p 519) Infrared Absorption Frequencies C O

12. Structural unitFrequency, cm -1 Bending vibrations of alkenes Table 13.4 (p 519) Infrared Absorption Frequencies CH 2 RCH R2CR2CR2CR2C CHR' cis-RCH CHR' trans-RCH CHR' R2CR2CR2CR2C910-990 890 665-730 960-980 790-840

13. Infrared spectrum of 1-hexene Transmittance (%) 100 0 Wave number, cm -1 440036002800200016001200800 C=C stretch CH 2 =C— bend

14. Infrared spectrum of tert-butylbenzene Transmittance (%) 100 0 Wave number, cm -1 440036002800200016001200800 Ar—H stretch; > 3000 monosubstituted benzene

15. Structural unitFrequency, cm -1 Stretching vibrations (single bonds) O—H (alcohols)3200-3600 O—H (carboxylic acids) 3000-3100 N—H3350-3500 Table 13.4 (p 519) Infrared Absorption Frequencies

16. Infrared spectrum of 2-hexanol Transmittance (%) 100 0 Wave number, cm -1 440036002800200016001200800 O—H stretch C—H stretch

17. Infrared spectrum of 2-hexanone Transmittance (%) 100 0 Wave number, cm -1 440036002800200016001200800 C=O stretch C—H stretch