Spectroscopynuclear magnetic resonance
The nmr spectra included in this presentation havebeen taken from the SDBS database with permission.National Institute of ...
Nuclear Magnetic Resonance (nmr)-the nuclei of some atoms spin: 1H, 13C, 19F, …-the nuclei of many atoms do not spin: 2H, ...
magnetic field = 14,092 gaussfor 1H v = 60,000,000 Hz (60 MHz)nmr spectrum                         magnetic field     int...
1 H nuclei are shielded by the magnetic field produced by thesurrounding electrons. The higher the electron density around...
Information from 1H-nmr spectra:3. Number of signals: How many different types of   hydrogens in the molecule.4. Position ...
1. Number of signals: How many different types of   hydrogens in the molecule.Magnetically equivalent hydrogens resonate a...
number of signals?                     H3C       CH3                           C                           C              ...
CH3H3C C CH3       CH3CH2-Br    Br                  two   oneCH3CH2CH2-Br   CH3CHCH3                  Cl  three           ...
CH3CHCH2CH3            Cl-CH2CH2CH2-Cl   Br four                       two              CH3                    CH2Cl      ...
1. Position of signals (chemical shift): what types of   hydrogens.   primary     0.9 ppm   secondary   1.3               ...
reference compound = tetramethylsilane (CH3)4Si @ 0.0 ppmremember:             magnetic field                        che...
toluene                  CH3              b   a          b             a
chemical shifts                          H3C       CH3                                C                  a             C  ...
a        a   b    CH3H3C C CH3       CH3CH2-Bra   Br  aa   b   c       a b aCH3CH2CH2-Br   CH3CHCH3                  Cl
b   d c a              b a bCH3CHCH2CH3         Cl-CH2CH2CH2-Cl   Br                a              CH3                    ...
1. Integration (relative areas under each signal): how   many hydrogens of each type. a b cCH3CH2CH2Br         a   3H     ...
integration                       H3C       CH3                             C               a             C               ...
a     a   b    CH3H3C C CH3       CH3CH2-Bra   Br  a                 a 3H    a 9H         b 2Ha    b     c    a b aCH3CH2C...
b   d c a              b a bCH3CHCH2CH3         Cl-CH2CH2CH2-Cl   Br a   3H                      a 2H b   3H              ...
c                       b                     aIntegration: measure the height of each “step” in the integration and thenc...
If the formula is known ( C8H9OF ), add up all of the “steps” and divide bythe number of hydrogens = (24 + 16 + 32 mm) / 9...
1. Splitting pattern: how many neighboring hydrogens.In general, n-equivalent neighboring hydrogens will split a    1     ...
note: n must be equivalent neighboring hydrogens togive rise to a Pascal splitting pattern. If the neighborsare not equiva...
splitting pattern?                          H3C        CH3                                 C               a              ...
a            a   b    CH3H3C C CH3            CH3CH2-Bra   Br  a                      a 3 H triplet    a 9 H singlet     b...
b   d c a                         b a bCH3CHCH2CH3                    Cl-CH2CH2CH2-Cl   Br    a   3H    triplet           ...
Information from 1H-nmr spectra:3. Number of signals: How many different types of   hydrogens in the molecule.4. Position ...
cyclohexane              a   singlet   12H
2,3-dimethyl-2-buteneH3C   CH3   C C        a singlet 12HH3C   CH3
benzene          a   singlet 6H
p-xylene   H3C          CH3           a             a                  b                 a singlet 6H                 b si...
tert-butyl bromide     CH3      a singlet 9H H3C C CH3     Br
ethyl bromide a bCH3CH2-Bra triplet 3Hb quartet 2H
1-bromopropane a b cCH3CH2CH2-Bra   triplet 3Hb   complex 2Hc   triplet  3H
isopropyl chloride a b aCH3CHCH3   Cla doublet 6Hb septet  1H
2-bromobutane b d c aCH3CHCH2CH3   Bra    triplet   3Hb   doublet    3Hc   complex    2Hd   complex    1H
o-methylbenzyl chloride      a    CH3     b          CH2Clc      a singlet 3H       b singlet 2H       c ~ singlet 4H
ethanol a c     bCH3CH2-OHa triplet 3Hb singlet 1Hc quartet 2H
cethylbenzene            b a                       CH2CH3               a triplet 3H               b quartet 2H           ...
p-diethylbenzene                   a   b   c   b   a               CH3CH2          CH2CH3               a triplet 6H      ...
m-diethylbenzene
o-diethylbenzene
2-bromo-2-methylbutane         b     CH3b CH3CCH2CH3 a     Br ca triplet 3Hb singlet 6Hc quartet 2H   b & c overlap
di-n-propylether a b c       c b aCH3CH2CH2-O-CH2CH2CH3a triplet 6Hb complex 4Hc triplet 4H
1-propanol a b d cCH3CH2CH2-OHa   triplet 3Hb   complex 2Hc   singlet 1Hd   triplet 2H
C11H16  a 9H = 3CH3, no neighbors                                                9H  c 5H = monosubstituted benzene  b 2H,...
C4H8Br2a = 6H, two CH3 with no neighbors                                       6H  (CH3)2C—b = CH2, no neighbors & shifted...
C7H8O                c = monosubst. benzene           5H   b = CH2      OHH2C             c = OH                   2H     ...
C4H9Br         a doublet 1.04 ppm   6H         b complex 1.95 ppm   1H         c doublet 3.33 ppm   2Ha = two equivalent C...
C10H13Cla singlet 1.57 ppm 6Hb singlet 3.07 ppm 2Hc singlet 7.27 ppm 5Ha = two-equilalent CH3’s with no neighborsc = monos...
13     C – nmr              C ~ 1.1% of carbons                         13•     number of signals: how many different type...
C-nmr13     2-bromobutane     a c   d b     CH3CH2CHCH3           Br
mrimagneticresonanceimagingThis image iscopyrighted, andused by kindpermission ofJoseph Hornak foruse in Chem-312.        ...
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Nmr

  1. 1. Spectroscopynuclear magnetic resonance
  2. 2. The nmr spectra included in this presentation havebeen taken from the SDBS database with permission.National Institute of Advanced Industrial Science and Technology (http://www.aist.go.jp/RIODB/SDBS/menu-e.html)
  3. 3. Nuclear Magnetic Resonance (nmr)-the nuclei of some atoms spin: 1H, 13C, 19F, …-the nuclei of many atoms do not spin: 2H, 12C, 16O, …-moving charged particles generate a magnetic field ()-when placed between the poles of a powerful magnet,spinning nuclei will align with or against the applied fieldcreating an energy difference. Using a fixed radio frequency,the magnetic field is changed until the ΔE = EEM. When theenergies match, the nuclei can change spin states (resonate)and give off a magnetic signal. ΔE
  4. 4. magnetic field = 14,092 gaussfor 1H v = 60,000,000 Hz (60 MHz)nmr spectrum magnetic field  intensity 10 9 8 7 6 5 4 3 2 1 0 chemical shift (ppm)
  5. 5. 1 H nuclei are shielded by the magnetic field produced by thesurrounding electrons. The higher the electron density aroundthe nucleus, the higher the magnetic field required to causeresonance. CH3Cl versus CH4lower electron higher electrondensity densityresonate at lower resonate at higherapplied field applied fieldCHCCl3 ??
  6. 6. Information from 1H-nmr spectra:3. Number of signals: How many different types of hydrogens in the molecule.4. Position of signals (chemical shift): What types of hydrogens.5. Relative areas under signals (integration): How many hydrogens of each type.6. Splitting pattern: How many neighboring hydrogens.
  7. 7. 1. Number of signals: How many different types of hydrogens in the molecule.Magnetically equivalent hydrogens resonate at the same applied field.Magnetically equivalent hydrogens are also chemically equivalent.# of signals? CH4 CH3CH3
  8. 8. number of signals? H3C CH3 C C H3C CH3 one one CH3 CH3 one two
  9. 9. CH3H3C C CH3 CH3CH2-Br Br two oneCH3CH2CH2-Br CH3CHCH3 Cl three two
  10. 10. CH3CHCH2CH3 Cl-CH2CH2CH2-Cl Br four two CH3 CH2Cl three
  11. 11. 1. Position of signals (chemical shift): what types of hydrogens. primary 0.9 ppm secondary 1.3 Note: combinations may tertiary 1.5 greatly influence chemical shifts. For example, the aromatic 6-8.5 benzyl hydrogens in benzyl allyl 1.7 chloride are shifted to lower benzyl 2.2-3 field by the chlorine and chlorides 3-4 H-C-Cl resonate at 4.5 ppm. bromides 2.5-4 H-C-Br iodides 2-4 H-C-I alcohols 3.4-4 H-C-O alcohols 1-5.5 H-O- (variable)
  12. 12. reference compound = tetramethylsilane (CH3)4Si @ 0.0 ppmremember: magnetic field   chemical shiftconvention: let most upfield signal = a, next most upfield =b, etc. … c b a tms
  13. 13. toluene CH3 b a b a
  14. 14. chemical shifts H3C CH3 C a C a H3C CH3 CH3 a a b CH3 a
  15. 15. a a b CH3H3C C CH3 CH3CH2-Bra Br aa b c a b aCH3CH2CH2-Br CH3CHCH3 Cl
  16. 16. b d c a b a bCH3CHCH2CH3 Cl-CH2CH2CH2-Cl Br a CH3 CH2Cl b c
  17. 17. 1. Integration (relative areas under each signal): how many hydrogens of each type. a b cCH3CH2CH2Br a 3H a:b:c=3:2:2 b 2H c 2H a b aCH3CHCH3 a 6H a:b=6:1 Cl b 1H
  18. 18. integration H3C CH3 C a C a H3C CH3 a 12 H a 12 H CH3 a a b CH3 a 6H a a 6H b 4H
  19. 19. a a b CH3H3C C CH3 CH3CH2-Bra Br a a 3H a 9H b 2Ha b c a b aCH3CH2CH2-Br CH3CHCH3 Cl a 3H b 2H a 6H c 2H b 1H
  20. 20. b d c a b a bCH3CHCH2CH3 Cl-CH2CH2CH2-Cl Br a 3H a 2H b 3H b 4H c 2H a d 1H CH3 CH2Cl b a 3H c b 2H c 4H
  21. 21. c b aIntegration: measure the height of each “step” in the integration and thencalculate the lowest whole number ratio: a:b:c = 24 mm : 16 mm : 32 mm= 1.5 : 1.0 : 2.0  3H : 2H : 4H
  22. 22. If the formula is known ( C8H9OF ), add up all of the “steps” and divide bythe number of hydrogens = (24 + 16 + 32 mm) / 9H = 8.0 mm / Hydrogen. a = 24 mm / 8.0 mm/H  3 H; b = 16 mm/8.0 mm/H  2H;c = 32 mm/8.0 mm/H  4H.
  23. 23. 1. Splitting pattern: how many neighboring hydrogens.In general, n-equivalent neighboring hydrogens will split a 1 H signal into an ( n + 1 ) Pascal pattern.“neighboring” – no more than three bonds away n n+1 Pascal pattern: 0 1 1 singlet 1 2 1 1 doublet 2 3 1 2 1 triplet 3 4 1 3 3 1 quartet 4 5 1 4 6 4 1 quintet
  24. 24. note: n must be equivalent neighboring hydrogens togive rise to a Pascal splitting pattern. If the neighborsare not equivalent, then you will see a complex pattern(aka complex multiplet).note: the alcohol hydrogen –OH usually does not splitneighboring hydrogen signals nor is it split. Normallya singlet of integration 1 between 1 – 5.5 ppm(variable).
  25. 25. splitting pattern? H3C CH3 C a C a H3C CH3 a 12 H singlet a 12 H singlet CH3 a a b CH3 a 6 H singlet a a 6 H singlet b 4 H singlet
  26. 26. a a b CH3H3C C CH3 CH3CH2-Bra Br a a 3 H triplet a 9 H singlet b 2 H quarteta b c a b aCH3CH2CH2-Br CH3CHCH3 Cl a 3 H triplet b 2 H complex a 6 H doublet c 2 H triplet b 1 H septet
  27. 27. b d c a b a bCH3CHCH2CH3 Cl-CH2CH2CH2-Cl Br a 3H triplet a 2 H quintet b 3H doublet b 4 H triplet c 2H complex d 1H complex a CH3 a b c CH2Cl CH3CH2-OH b a 3 H tripletc a 3 H singlet b 2 H quartet b 2 H singlet c 1 H singlet c 4 H ~singlet
  28. 28. Information from 1H-nmr spectra:3. Number of signals: How many different types of hydrogens in the molecule.4. Position of signals (chemical shift): What types of hydrogens.5. Relative areas under signals (integration): How many hydrogens of each type.6. Splitting pattern: How many neighboring hydrogens.
  29. 29. cyclohexane a singlet 12H
  30. 30. 2,3-dimethyl-2-buteneH3C CH3 C C a singlet 12HH3C CH3
  31. 31. benzene a singlet 6H
  32. 32. p-xylene H3C CH3 a a b a singlet 6H b singlet 4H
  33. 33. tert-butyl bromide CH3 a singlet 9H H3C C CH3 Br
  34. 34. ethyl bromide a bCH3CH2-Bra triplet 3Hb quartet 2H
  35. 35. 1-bromopropane a b cCH3CH2CH2-Bra triplet 3Hb complex 2Hc triplet 3H
  36. 36. isopropyl chloride a b aCH3CHCH3 Cla doublet 6Hb septet 1H
  37. 37. 2-bromobutane b d c aCH3CHCH2CH3 Bra triplet 3Hb doublet 3Hc complex 2Hd complex 1H
  38. 38. o-methylbenzyl chloride a CH3 b CH2Clc a singlet 3H b singlet 2H c ~ singlet 4H
  39. 39. ethanol a c bCH3CH2-OHa triplet 3Hb singlet 1Hc quartet 2H
  40. 40. cethylbenzene b a CH2CH3 a triplet 3H b quartet 2H c ~singlet 5H
  41. 41. p-diethylbenzene a b c b a CH3CH2 CH2CH3 a triplet 6H b quartet 4H c singlet 4H
  42. 42. m-diethylbenzene
  43. 43. o-diethylbenzene
  44. 44. 2-bromo-2-methylbutane b CH3b CH3CCH2CH3 a Br ca triplet 3Hb singlet 6Hc quartet 2H b & c overlap
  45. 45. di-n-propylether a b c c b aCH3CH2CH2-O-CH2CH2CH3a triplet 6Hb complex 4Hc triplet 4H
  46. 46. 1-propanol a b d cCH3CH2CH2-OHa triplet 3Hb complex 2Hc singlet 1Hd triplet 2H
  47. 47. C11H16 a 9H = 3CH3, no neighbors 9H c 5H = monosubstituted benzene b 2H, no neighbors c b a CH3 CH2 C CH3 CH3 neopentylbenzene 2H 5H
  48. 48. C4H8Br2a = 6H, two CH3 with no neighbors 6H (CH3)2C—b = CH2, no neighbors & shifteddownfield due to Br CH3 2H H3C C CH2 Br Br
  49. 49. C7H8O c = monosubst. benzene 5H b = CH2 OHH2C c = OH 2H 1H
  50. 50. C4H9Br a doublet 1.04 ppm 6H b complex 1.95 ppm 1H c doublet 3.33 ppm 2Ha = two equivalent CH3’s with one neighboring H (b?)c = CH2 with one neighbor H (also b) a CH3 a 6H doublet CH3CHCH2Br b 1H complex a b c c 2H doublet
  51. 51. C10H13Cla singlet 1.57 ppm 6Hb singlet 3.07 ppm 2Hc singlet 7.27 ppm 5Ha = two-equilalent CH3’s with no neighborsc = monosubstituted benzene ringb = CH2 a singlet 6H a b CH3 b singlet 2H c c singlet 5H CH2 C CH3 Cl
  52. 52. 13 C – nmr C ~ 1.1% of carbons 13• number of signals: how many different types of carbons• splitting: number of hydrogens on the carbon• chemical shift: hybridization of carbon sp, sp2, sp3• chemical shift: evironment
  53. 53. C-nmr13 2-bromobutane a c d b CH3CH2CHCH3 Br
  54. 54. mrimagneticresonanceimagingThis image iscopyrighted, andused by kindpermission ofJoseph Hornak foruse in Chem-312. http://www.cis.rit.edu/htbooks/mri/

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