SlideServe
Télécharger Obtenir Pro
Menu
Accueil Pro
Préférences
ApparenceLight Aide et commentaires
© SlideServe · v2026

Infrared Spectroscopy

ponce avatar
ponce
24 diapositives · 938 Views · Aug 21, 2012

Infrared Spectroscopy. Chapter 12. Energy. Table 12.1, p.472. Final Exam Schedule, Thursday, May 22, 10:30 AM. Infrared spectroscopy causes molecules to vibrate.

#raman spectroscopy #vibrational spectroscopy #microwave spectroscopy #electron spin resonance #electron paramagnetic resonance #esr #etalon #astronomical spectroscopy
Infrared Spectroscopy - slide 1
01 / 24Infrared Spectroscopy
1 / 17

Télécharger la présentation

Infrared Spectroscopy
Une image / un lien ci-dessous est fourni (tel quel) pour télécharger la présentation

Politique de téléchargement : le contenu du site vous est fourni TEL QUEL pour votre information et votre usage personnel ; il ne peut être vendu, concédé sous licence ni partagé sur d’autres sites sans l’accord de son auteur.Le contenu vous est fourni TEL QUEL, pour votre information et votre usage personnel uniquement. Téléchargez la présentation en cliquant sur ce lien. Lors du téléchargement, si vous ne parvenez pas à télécharger une présentation, l’éditeur a peut-être supprimé le fichier de son serveur.Pendant le téléchargement, si vous ne parvenez pas à obtenir une présentation, le fichier a peut-être été supprimé par l’éditeur.

F I N

Plus de contenu associé

Transcription de la présentation

  1. Infrared Spectroscopy Chapter 12

  2. Energy Table 12.1, p.472

  3. Final Exam Schedule, Thursday, May 22, 10:30 AM

  4. Infrared spectroscopy causes molecules to vibrate

  5. A non-linear molecule having n atoms may have many different vibrations. Each atom can move in three directions: 3n. Need to subtract 3 for translational motion and 3 for rotations # vibrations = 3 n – 6 (n = number of atoms in non-linear molecule) Infrared radiation does not cause all possible vibrations to vibrate. For a vibration to be caused by infrared radiation (infrared active) requires that the vibration causes a change in the dipole moment of the molecule. (Does the moving of the atoms in the vibration causes the dipole to change. Yes: should appear in spectrum. No: should not appear.) Consider C=C bond stretch… ethylene 1,1 difluoro ethylene What about 1,2 difluoro ethylene?

  6. Different bonds have different resistances to stretching, different frequencies of vibration Table 12.4, p.478

  7. Typical Infra-red spectrum. wavelength Frequency, measured in “reciprocal centimeters”, the number of waves in 1 cm distance. Energy. Figure 12.2, p.475

  8. “fingerprint region”, complex vibrations of the entire molecule. C=O C-H Vibrations characteristic of individual groups. Figure 12.2, p.475

  9. BDE of C-H 414 464 556 472 Table 12.5, p.480

  10. BDE and CC stretch 376 727 966 Table 12.5, p.480

  11. Alkane bands Figure 12.4, p.480

  12. Recognition of Groups: Alkenes (cyclohexene). Compare these two C-H stretches Sometimes weak if symmetric

  13. Recognition of Groups: Alkynes (oct-1-yne) • This is a terminal alkyne and we expect to see • Alkyne C-H • Alkyne triple bond stretch (asymmetric)

  14. Recognition of Groups: Arenes. (methylbenzene, toluene) Out-of-plane bend; strong

  15. Recognition of Groups: Alcohols The O-H stretch depends on whether there is hydrogen bonding present Compare –O-H vs -O-H….O Hydrogen bonding makes it easier to move the H with H bonding as it is being pulled in both directions; lower frequency

  16. Recognition of Groups: Alcohols

  17. Recognition of Groups: Ethers No O-H bond stretch present but have C-O in same area as for alcohol.

  18. C-O stretch in assymetric ethers

  19. Recognition of Groups: Amines Easiest to recognize is N-H bond stretch: 3300 – 3500 cm-1. Same area as alcohols. Note tertiary amines, NR3, do not have hydrogen bonding. Hydrogen bonding can shift to lower frequency

  20. Esters One C=O stretch and two C-O stretches.

  21. Recognition of Groups: Carbonyl • C=O stretch can be recognized reliably in area of 1630 – 1820 cm-1 • Aldehydes will also have C(O)-H stretch • Esters will also have C-O stretch • carboxylic acid will have O-H stretch • Amide will frequently have N-H stretch • Ketones have nothing extra

  22. What to check for in an IR spectrum C-H vibrations about 3000 cm-1 can detect vinyl and terminal alkyne hydrogens. O-H vibrations about 3500 cm-1 C=O vibrations about 1630 – 1820 cm-1 C-O vibrations about 1000-1250 cm-1