Kuliah NMR Lengkap1

8/18/2019 Kuliah NMR Lengkap1

1/65

Nuclear Magnetic Resonance

(NMR) Spectroscopy


2/65

Proses Resonansi• Atom: inti dan elektron

• Inti mempunyai bil. spin momen spin• !il. Spin I" # $ %%$ &'• I"# bila proton dan netron ganil• Inti % and %*+ I: ,%-& dan %-&• Spinning c/arge spinning nucleus /as a

magnetic moment t/at coincides 0it/t/e a1is o2 rotation.• 3nder normal circumstances t/e t0o

spin states are energeticallye4ui5alent.

• Spinning nuclei precesses along a1is o2

spin in concert 0it/ t/e orientation0it/ t/e magnetic 2ield.∀ ω re2ers to angular 2re4uency o2

nuclear precession.

ω

AppliedMagnetic 6ield

Precessional motion of aspinning nucleus


3/65

Not all elements/isotopes are NMR active.

• Nuclei with even mass number and even atomic number have

nuclear spin quantum number (I=0) of zero

• Odd mass number and even/odd atomic number have

I=1/2

• Even mass number but odd atomic number have integer values

I= 1,2, 3, etc

Only nuclei with non zero nuclear spin give NMR spectra

13C vs. 12C The natural abundance of 13C is approximately 1%

The natural abundance of 12C is approximately 99%


4/65

• Keadaan normal (tdk ada medan

magnet) spin inti mempunyai energi yg

sama.

•Dlm medan magnet, terjadi dua orientasienergi

• Perbedaan energi tergantung pada

medan magnet yg digunakan

H0 14100 gauss ∆! "0#H$

H0 %&'00 gauss ∆! 100#H$• Pada keaaan ini bila energi dr luar

diberikan spin inti dapat lip*. +ni

proses esonansi

• nergi luar (gel radio) -arus sama

dengan perbedaan energi yg dibutu-kan.h ν

Applied

Magnetic6ield

.%-&

,%-&

H0

∆ E ∆ E'

E1

E2

E'1

E'2

H0 H'0


5/65

Peralatan CW NMR


6/65

Frequensi Vs Medan magnet

• Proton mempunyai frequensi tertentu padakeadaan resonansi

• Faktor yang mempengaruhi adalah faktorlindungan (shielding) elektron yangmenyelimuti inti

• Lindungan ditentukan oleh induksi danmomen magnet yang disebabkan oleh awanelektron


7/65

+/emical S/i2t

• A molecule may contain multipleprotons that exist in uniqueelectronic environments.

• Therefore not all protons are

shielded to the same extent.• Resonance differences in protons

are very small (ppm).

• Measure differences in resonanceenergy relative to a reference.

• etramet-ylsilane (/H&)4i(#) proides -ig-ly s-ieldedreeren2e (set to 0ppm).

Nuclear Shielding

• Nuclei are shielded by

electrons.•

Induced field associated withorbiting electrons.• Require stronger magnetic field

than H0.

• Increased shielding requires

greater applied field strength to

achieve resonance.

Chemical Shift (δ, ppm) =Observed chemical shift from TMS (Hz)

Sptectrometer frequencey (MHz)

= ppm


8/65

NMR Spectra

• Hypothetical NMR spectra.

• Shows TMS reference.

• Chemical shifts (δ, ppm) given relative to TMS

0123456789101112

Increasing magnetic field strength

δ, ppm

TMS

C

H

H

H

TMS as referenceis set to 0 ppm

Representative peak,3 equivalent protons

Increased sheilding of nuclei


9/65

+/emically 74ui5alent• Protons in the same

environment will have thesame chemical shift.

• Protons in different

environments havedifferent chemical shifts.

• Protons with the samechemical shift are referred

to as chemicallyequivalent.

• Integrated area of peak isproportional to the numberof protons.

H

H

H

H

H

H

C

C

H

H

H

H

H

H

H

C

H

H

H

H

H

H

H

C

C

H

H

H

H

C

H

H H

H


10/65

Sample Spectra

• The first spectra is that

of a symmetric

molecule, all protons are

equivalent.

• Second spectra is that of

a molecule containing

two types of protons.

• Correlation chart for

proton chemical shift

has been studied.

0123456789101112 δ, ppm

TMS

C

C

H

H

H

H

H

H

0123456789101112 δ, ppm

TMS

H

CH

H

HH

H

H

H


11/65

CH3CHCH2CCH3

OCH3

chemical shift = 25 ppm





Sample Carbon Spectrum: 4-methyl-2-pentanone


12/65

Shielding: Magnetic Fields

1. External Magnetic Field (B0)

2. Induced Magnetic Field Caused by Circulating Electrons


13/65

Proton Chemical Shifts of ethyl !erivatives

Proton Chemical Shifts "ppm#

Compound (CH3)4C (CH3)3N (CH3)2O CH3F

0.9 2.1 3.2 4.1

Compound (CH3)4Si (CH3)3P (CH3)2S CH3Cl

0.0 0.9 2.1 3.0

Cpd. / Sub. X=Cl X=Br X=I X=OR X=SR

CH3X 3.0 2.7 2.1 3.1 2.1

CH2X

2 5.3 5.0 3.9 4.4 3.7

CHX3 7.3 6.8 4.9 5.0


14/65

Tabel pergeseran Kimia


15/65

Nuclear S/ielding-8es/ielding

• Valence electron densitycan shield nucleus fromapplied field.

•Electronegativesubstituents can drawelecron density away.

• Results in deshielding.

• Anisotropy: π-electrons

and induced magneticfield.

• Results in shielding anddeshielding zones.

H

H0

O HH

/H&3 /H&/l /H%/l% /H&/H& /H&/H&

δ (ppm) 4,& &,1 ',4 &,% 0,5


16/65

Spektra 1H NMR

• Spektra CH3CH2OH bila tidak terjadi

spliting

• OH CH2 CH3


17/65

Spektra C2H6O (terjadi pemecahan)


18/65


19/65

Spinspin Splitting and n,% Rule

• Each type of proton “senses”

protons on adjacent carbon atoms.

• Spin state of nearby protons

contributes to the proton

evironment and apparent magnetic

field.• General rule is that the signal is

split into n! pea"s. n # number of

e$uivalent neighboring protons.

• Spacing bet%een componentpea"s referred to as coupling

constant &J '.

• J coupling is representative of the

degree to %hich protons interact.

• J usually ()!*H+

n # ,- tripletn # !- doublet

-1/2 +1/2 0 +1 -1

n # - $uartet

-1/2 +1/2

-1 1/2 +1 1/2

Numbers in Italics refer to net spin

Splittin$

n # (- singlet

Cl C

Ha

Cl

C

Hb

Hb

Cl Cl C

Ha

Cl

C

Hb

Hb

Cl

e$uivalentprotons behave

as a group

/%o types of protons in !-!-,)trichloroethane


20/65

n # ,- tripletn # !- doublet

-1/2 +1/2 0 +1 -1

n # .- $uartet

-1/2 +1/2

-1 1/2 +1 1/2

Numbers in Italics refer to net spin

Splittin$

n # (- singlet


21/65

Multiplicity

singlet

Doublet

Triplet

Quartet

Quintet


22/65


23/65

struktur

struktur


24/65


25/65


26/65

%%&tric/loroet/ane

• NMR spectrum for 1,1,2-trichloroethane

• Hb proton signal split into doublet

• Ha proton signal split into triplet

• J couplings are the same for Ha and Hb signals

• Ha integral is 1/2 that of Hb

(!,0123* δ, ppm

TMS

Cl C

Ha

Cl

C

Hb

Hb

Cl

J J

J

Hb

Ha


27/65

Coupling constant J


28/65


29/65


30/65


31/65


32/65

Magnitude of Some Typical Coupling Constants

<


33/65

Magnetic 74ui5alence 5s.

+/emical 74ui5alence• NMR differentiates

between nuclei based onenvironment.

• In constrained systems,two protons on the sameC-atom can be in differentenvironments.

• These protons candemonstrate spin-spinsplitting.

• Geminal coupling

• J geminal ~5Hz

Ha

HbH3C

Br

Br

H3C

X

HcHa

Hb


34/65


35/65

Diagram KarplusDiagram Karplus


36/65

4)O)H 5,O 4)O)5 5)O)H

Ikatan Hidrogen


37/65

ig/er 6ield Strengt/s

• At higher field strengths

differences in energy

between spin states is

increases.

• Improved signal

resolution.

• Coupling constants are

independent of fieldstrength.

(!,0123* δ, ppm

(!,0 δ, ppm

/6S

/6S

2( 6H+

!(( 6H+

2( 6H+

!(( 6H+

7hemical Shift &δ- ppm' #Observed chemical shift from /6S &H+'

Sptectrometer fre$uencey &6H+' # ppm


38/65


39/65

Chemical shift Reagent


40/65


41/65


42/65

Pereasi Per$eseran imia


43/65

Integrasi


44/65


45/65


46/65

Tentukan Struktur senyawa dari spektra NMR proton berikut:


47/65


48/65

C10 H14 O


49/65

Tentukan struktur dari data berikut:


50/65

Rumus molekul C3H8O

http://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/PROB1A.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/PROB1A.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/PROB1A.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/PROB1.HTM


51/65

http://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTM


52/65

Rumus molekul C6H12

http://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/PROB2A.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/PROB2A.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/PROB2A.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/PROB2.HTM


53/65

http://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTMhttp://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/IRHELP.HTM


54/65

Rumus Molekul C5H10O

http://www.chem.uic.edu/web1/OCOL-II/WIN/SPEC/PROBLEMS/PROB3.HTM


55/65


56/65

+arbon%* NMR

• ~1.08% of C atoms are the 13C isotope.

• Do not usually see C-C spin-spin interactions.

• Can see coupling between C and attached H’s.

• Magnetic moment µ of 13C is low.• Resonances of 13C nuclei are ~6000 fold weaker than 1H

resonances.

• Therefore most useful information is chemical shift.

• Covers a range of 0-200ppm.• Influence chemical shift in proton spectra also influence

in carbon spectra


57/65

Spektra NMR Carbon 4-bromoacetofenon


58/65

Per$eseran imia atom &arbon


59/65

Perbedaan atom arbon dalam 13C '(


60/65


61/65

Proton 8ecoupled

• Proton coupling canprovide informationabout number of protons.

• Often useful to decoupleprotons.

• Irradiate sample withbroad spectrum offrequencies.

• Substituents on C canenhance of reduce signal.

• Protons enhance the 13Csignal.

( δ, ppm

TMS

OH,7

H,7

O

7H

,(0(2(*(!((!,(!0(!2(!*(

8ndecoupled

5ecoupled from protons

O 7H, 7H

H,7 7

O12

3

4

5

6

!

,-2-1

07O


62/65


63/65

(umus oleul C)*+,2'


64/65

Rumus Molekul C6H8O

R M l k l C H O


65/65

Rumus Molekul C8H8O

Documents

Kuliah NMR Lengkap1