Bloco de Ressonância Magnética Nuclear

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1 Mestrado em Química, Métodos Avançados de Análise 2017/2018 Bloco de Ressonância Magnética Nuclear Parte 2 14 de Novembro 2017 Helena Gaspar hmgaspar@ciencias.ulisboa.pt Gab , Lab

2 2 Why performed 13 C NMR? if 13 C carbon thirteen is 6400 times less sensitive than Proton 1 H More samples amounts More time experience (more number of scans ns more FIDs)

3 3 Why to perform 13 C NMR? When significant portions of a molecule lack C-H bonds

4 4 Why performed 13 C NMR? When compounds display similar proton nmr spectra and might be difficult to distinguish them by proton nmr alone

5 5 Why performed 13 C NMR? Carbons resonate from ~0-220 ppm relative to the TMS standard, as opposed to only ~0-12 ppm for protons We can distinguish separate peaks for each carbon, even in a relatively large compound containing carbons in very similar environments, even if it is not possible to distinguish the corresponding protons

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8 8 Interpretation of 13 C NMR spectra Chemical shift (depends on the chemical surrounding) How many types of C are in the molecule It s diaganostic of the chemical environment (shielding/deshilding) Signal multiplicity (spliting) (splitting due to the surrounding nuclei) What are the surronding nucleus connectivity in the molecule Carbon types: C, CH, CH 2,CH 3

9 9 Structural information of molecules 13 C NMR Table Carbon chemical shift ranges 13 C NMR chemical shift depends on chemical surrounding Low Field Region High Field Region Carbon chemical shift range (220-0 ppm) ref TMS

10 10 Signal multiplicity - spin-spin coupling Homonuclear coupling spin-spin coupling between neighboring carbons in not observed due the low natural abundance of 13 C nuclei (<1%) Heteronuclear coupling spin-spin coupling between carbons and the hydrogens (n+1 rule) with J CH Hz Information distinguishing between a C, CH 3, a CH 2, and a CH groups

11 11 Carbon Types Primary Secondary tertiary Quaternary

12 12 Bromobutane BrCH 2 CH 2 CH 3 13 C NMR 13 CH 2 13 CH 2 13 CH ppm

13 13 13 C NMR CDCl 3 ethylbenzene Very complex!

14 14 Number spin states = 2 I +1, I=1/2 ( 1 H, 13 C), 2 spin states I=1 (2H deuterium D), 3 spin states Signal Multiplicity= 2nI + 1

15 15 13 C Deuterated solvents, deuterium (D) I=1 Signal Multiplicity= 2nI + 1 Chloroform CDCl 3 Acetone CD 3 COCD 3 Dimethyl sulfoxide CD 3 SOCD 3 Methanol CD 3 OD n=1 triplet n=3 septet and C=O singlet n=3 septet n=3 septet

16 16 Signal Multiplicity= 2nI + 1 deuterium (D) I=1 CDCl 3 n=1 SM=3 triplet CD 3 COCD 3 n=3 SM=7 septet C=O singlet Structure Determination of Organic Compounds, Tables of Spectral Data, Pretsch, Buhlmann, Badertscher, 4Th edition, 2009

17 17 Signal Multiplicity= 2nI + 1 deuterium (D) I=1 CD 3 SOCD 3 n=3 SM =7 septet CD 3 OD n=3 SM =7 septet Structure Determination of Organic Compounds, Tables of Spectral Data, Pretsch, Buhlmann, Badertscher, 4Th edition, 2009

18 18 How to remove all heteronuclear coupling 13 C- 1 H? Broadband decoupling ( 13 C { 1 H}) - by irradiation of all protons resonance the spin-spin coupling (J CH ) is suppressed (decoupled), resulting in all signals appearing as singlets and with lagers intensities due to the Nuclear Overhauser Enhancement (NOE) NOE -The irradiation of protons resonance increase the signal of attached carbon (4x more, due g 1 H/g 13 C =~4) Major number of protons => greater increase of intensity Integration of 13 C signal area is not proportional to the number of carbon that give rise that resonance

19 19 [rel] C- 1 H decoupling EB simplify 31 1 C:\Bruker\TOPSPIN and facilitates Aulas the interpretation 13 C NMR 13 C NMR ethylbenzene 4x Broadband decoupling 13 C NMR 13 C { 1 H} 1x [ppm]

20 20 [rel] EB 31 1 C:\Bruker\TOPSPIN Aulas J CH may be greater than the difference between the chemical shifts 13 C NMR ethylbenzene 13 C { 1 H} [ppm]

21 21 Disadvantage in decoupling 13 C spectra the multiplicity signals is lost! the information about how many protons are coupled to each carbon is lost (C, CH, CH 2 and CH 3 carbons) How to obtain the lost information (multiplicity)? DEPT - Distortionless Enhancement by Polarization Transfer APT Attached Proton Test Are multiplet detection technique

22 22 Multipulse 13 C NMR experiments - DEPT It is a proton-carbon polarization transfer method Quaternary carbon atoms do not appear The intensity of carbon signals depends on 1 H pulse angle DEPT 45 ( = 45) show carbons that have attached hydrogen atoms (CH, CH 2, CH 3 ) DEPT 90 ( = 90) show carbons with a single attached hydrogen atom (CH) DEPT 135 ( = 135) distinguishes between carbon atoms based on their phasing CH and CH 3 carbon atoms are phased the same way (usually positive) CH 2 carbon atoms are phased the opposite way (usually negative) Information DEPT for distinguishing between a CH 3, a CH 2, and a CH groups

23 23 [rel] C NMR DEPT - ethylbenzene C CH CH 2 CH EB 31 1 C:\Bruker\TOPSPIN Aulas 13 C DEPT C DEPT CH, CH 3 CH 2 CH 13 C DEPT 45 + CH,CH 2,CH 3 13 C { 1 H} + C, CH,CH 2, CH [ppm] CDCl 3

24 24 Information DEPT for distinguishing between a CH 3, a CH 2, and a CH groups

25 [rel] [rel] Multipulse 13 C NMR experiment - APT EB 31 1 C:\Bruker\TOPSPIN Aulas APT Attached Proton Test It is a proton-carbon spin-echo experiment Quaternary carbon atoms are also observed EB 31 1 C:\Bruker\TOPSPIN Aulas 13 C APT ethylbenzene Positive CH,CH 3 Negative C,CH [ppm]

26 26 APT 13 C NMR Spectrum 2-nonanone + - CH 3 CH CH 2 C C=O CDCl 3

27 27 APT 13 C NMR Spectra 2 CH CH 3 CH CH 2 C 5 CH 2

28 28 2D NMR Two-dimensional nuclear magnetic resonance spectroscopy Homonuclear 1 H- 1 H COSY Corelation SpectroscopY TOCSY - TOtal Correlated SpectroscopY NOESY Nuclear Overhauser Effect SpectroscopY Heteronuclear 13 C- 1 H HSQC Heteronuclear Single-Quantum Correlation Spectroscopy HMQC - Heteronuclear Multiple-Quantum Correlation Sepectroscopy HMBC - Heteronuclear Multiple-Bond Correlation Spectroscopy HSQC-TOCSY HMQC-TOCSY

29 29 Itensity 2D NMR SPECTRA w o w o w o f 1 w o f 1 f 2 Tridimensional f 2 bidimensional

30 30 Homonuclear 1 H- 1 H COSY - COrrelationSpectroscopY Information what are the protons that have spin-spin coupling (H-H coupling through-bond) Diagonal peaks are the protons seeing themselves = 1D proton spectrum Cross peaks exist only when there is J coupling between protons

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33 33 Homonuclear 1 H- 1 H TOCSY- TOtal Correlated SpectroscopY Information what are the protons that have spin-spin coupling (H-H coupling through-bond) into groups (coupling networks) 5 J HH 4 J HH 3 J HH 3 J HH H H H H H H C C C C O C C

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35 35 H2, H1 H3, H4 H4, H5 H5, H6 H3, H6 H2, H1 H3, H5 H3, H4 H6,H3 5bonds

36 36 COSY TOCSY

37 37 COSY TOCSY

38 38 TOCSY OH 3 spin groups: H1,H2,H3,H4,H5,H6 H1 H3, H4, H5, H6

39 39 1-iodobutane 1-butanol OH CH 3 CH 3 CH 2 CH 2 2X CH 2 CH 2 CH 2 Organic Structures from Spectra, Field, Sternhell, Kalman, 4 th edition, 2007

40 40 1-iodobutane 1-butanol OH 1-iodobutane 1-butanol Organic Structures from Spectra, Field, Sternhell, Kalman, 4 th edition, 2007

41 41 1-iodobutane 1-butanol OH 1-iodobutane 1-butanol Organic Structures from Spectra, Field, Sternhell, Kalman, 4 th edition, 2007

42 42 1-iodobutane 1-butanol OH Organic Structures from Spectra, Field, Sternhell, Kalman, 4 th edition, 2007

43 43 1-iodobutane 1-butanol COSY OH OH TOCSY 0 Organic Structures from Spectra, Field, Sternhell, Kalman, 4 th edition, 2007

44 44 Homonuclear 1 H- 1 H NOESY - Nuclear Overhauser Effect SpectroscopY Information what are the protons that are close in space, distances < 5 Å (H-H coupling trougth-space) NOE correlation for distances < 5 Å Coupling trougth the space Diagonal peaks are the protons seeing themselves 1D proton spectrum Cross peaks exist only when there is NOE between protons (connect resonances from H that are spacially close)

45 45 NOESY 1 H NMR 1 H NMR

46 46 H8 H7 H7 Organic Structures from Spectra, Field, Sternhell, Kalman, 4 th edition, 2007 H8

47 47 H8 H7 H6 H6 H7 H8

48 48 H8 H5 H7 H6 H6 H7 H5 H8

49 49 H8 H4 H5 H7 H6 H6 H7 H5 H4 H8

50 50 H8 H4 H5 H7 H3 H6 H3 H6 H7 H5 H4 H8

51 51 H8 H2 H4 H5 H7 H3 H6 H3 H6 H7 H5 H4 H2 H8

52 52 H8 H2 H4 H5 H7 H3 H6 H3 H6 H7 H5 H4 H2 H8

53 53 NOESY

54 54 NOESY H-1 ax or eq?

55 55 Heteronuclear 13 C- 1 H HSQC Heteronuclear Single-Quantum Correlation Spectroscopy HMQC - Heteronuclear Multiple-Quantum Correlation Sepectroscopy Information what are the proton directly attached to a specific carbon (one bond correlation C-H) <> 1 J C-H H C Cross peaks exist only when there is a C-H bond ( 1 J C-H)

56 56 HMQC 1 H NMR 13 C NMR

57 57 HSQC 1 H NMR 13 C NMR

58 58 HSQC-Edet 1 H NMR C5 C4 C2 + C3 C3 HSQC-Dept135 C1 /C4 C2 Red (negative)- CH 2 Blue (negative)- CH or CH 3 13 C NMR C2 /C3 C α-pvp

59 59 HSQC-edet H a -1 H b -1 H a -4 H b -4 H-2 eq H-1,3 ax H-4,6 ax H-5ax H. Gaspar et al, 4F-PBP, a new substance of abuse: structural characterization and purity NMR profiling, Forensic. Science International 2015, (252) 168

60 60 Heteronuclear 13 C- 1 H HMBC - Heteronuclear Multiple Bond Quantum Information what are the protons that correlate to carbons at 2 and 3 bonds distance (long range coupling) <> 2 J C-H and 3 J C-H H C C C Cross peaks exist only when there is a proton-carbon correlation ( 2 J or 3 J)

61 61 H HMBC H6 H3 H H 6 C 3 H C 3 6 C C 5 7 C5 C C C

62 Heteronuclear 13 C- 1 H HMQC HSQC The correlations is used to establish C-H connectivity (How many types of C, CH, CH 2, CH 3 ) also from DEPT HMBC The correlations is used to establish C-C connectivity

63 63 Heteronuclear 13 C- 1 H HSQC-TOCSY or HMQC-TCOSY 2D TOCSY that has been resolved into the carbon dimension Information Proton coupling networks with a specific carbone.

64 64 Horizontal - Proton coupling networks with a specific carbone Vertical Specific proton with a carbone networks