irspectroscopy-220807044556-7f8726c4.ppt

pho ir ung dung trong hoa hoc huu co

1. INFRARED
SPECTROSCOPY

3. Electromagnetic Spectrum

4. Bond Stretching

5. High Frequency Stretching
Low Frequency Bending

6. Frequency of Absorption
Measured in cm
-1
(Wavenumbers)
Wavelength units typically microns (m)
10,000 m = 1 cm or 1m = 10-4 cm
Frequency units typically measured in cm-1
= # waves or cycles in 1 cm (wavenumbers)
Mid-Infrared frequency range is 4000 - 400 cm-1
(2.5 - 25 m)

7. High Frequency to Low Frequency
Functional Groups Region
4000 - 1400 cm-1
Fingerprint Region
1400-600 cm-1

8. General Trends:
i)
 
Stretching frequencies are higher than corresponding bending frequencies. (It is easier to bend a bond than to stretch or compress it.)
ii)
 
Bonds to hydrogen have higher stretching frequencies than those to heavier atoms.
iii)
 
Triple bonds have higher stretching frequencies than corresponding double bonds, which in turn have higher frequencies than single bonds. (Except for bonds to hydrogen).

11. IR Spectrum of Octane

12. Decane

13. 2,2,4-Trimethylpentane

14. Hybridization of Carbon
Affects of Absorption

15. Hexane and Hexene

16. 1-Pentene

17. 1-Dodecene

18. 2-Methyl-1,3-butadiene
(Isoprene)

19. Terminal Alkynes are Readily
Identifiable with IR

20. 1-Heptyne

21. Aromatics
•C-H str (sp
2
) at 3050-3100 cm-1
•C-C str (breathing) 1600 & 1500 cm
-1
H

22. Toluene

23. o-Xylene

24. Alcohols
O-H str at 3600-3200 cm
-1
C-O str at 1050-1150 cm
-1

25. Cyclohexanol

26. O-H Stretch

27. 2-Methyl-1-butanol

28. Benzyl alcohol

29. 1
o
Amines

30. 2-Methylpentanediamine

31. 2
o
Amine

32. Dipropylamine

33. Carbonyl Compounds

34. Acetone

35. Cycloheptanone

36. Acetophenone

37. Conjugation Lowers  of
Absorption

39. Ketone and Aldehyde

40. Octanal

41. Carboxylic Acid

42. Hexanoic Acid

43. Phenyl Acetate, an Ester

44. Ethyl Butanoate

45. Methyl Benzoate

46. Benzoic Anhydride, an
Acid Anhydride

47. Butanamide, an Amide

48. O

49. CH
3CH
2OCCH
3
O

50. CH
2CH
O

51. CN

52. CH
2=CHCH
2CH
2CH
3

53. HCCCH2CH2OH

54. CH
3CH
2CH
2NH
2

55. CH2CH2CH2CH2CO2H