Transcript NUCLEAR MAGNETIC RESONANCE (NMR) WIDIASTUTI AGUSTINA ES, S.Si., M.Si. Nuclear Magnetic Resonance Spectroscopy (NMR) : Spectroscopic technique that provide information about amount and type of atomic molecule 1H NMR •

NUCLEAR
MAGNETIC
RESONANCE
(NMR)
WIDIASTUTI AGUSTINA ES, S.Si., M.Si.
Nuclear Magnetic Resonance
Spectroscopy (NMR) :
Spectroscopic technique that provide
information about amount and type of
atomic molecule
1H NMR
• Hydrogen atoms
13C NMR
• Carbon atoms
31P NMR
• Phosphor atoms
NUCLEAR SPIN ATOM
- Electron have quantum number ½ with a value
of +1/2 and -1/2
- Spin Charge generates magnetic field so that
electron act as a tiny magnet called a
magnetic moment
- This effect also valid for another atom. An
atomic nucleus has an odd number and atomic
number of the odd or both will have to have
spin and produced magnetic moment
- Nuclear Spin Rate depends on the quantum
spin number , l, of nuclei
NUCLEAR SPIN NUMBER
1
Element
Nuclear spin
quantum
number ( I )
Number of
spin states
H
2
H
12
C
13
C
14
N
15
N
1/2
1
0
1/2
1
1/2
2
3
1
2
3
2
16
O
19
F
31
P
32
S
0 1/2 1/2
0
1
1
2
Number of spin state = 2 l +1
l = nuclear spin quantum number
2
SPIN STATE
Nuclear atomic spin with +
charge, generating a magnetic
moment vector
m
+
+
m
+ 1/2
- 1/2
Without magnetic field,
both spin state have the
same energy
IN MAGNETIC FIELD (BO)
RESONANCE
In NMR spectroscopy, resonance is the energy absorption by the
core-precision results in a change of spin nuclei from lower
energy level to a higher energy level
The precision results in a magnetic field oscillations and produce
a "signal"
quantized
-1/2
-1/2
DE = hn
DE
+1/2
Bo
Magnetic Field
In a strong
magnetic field,
a rotating nuclei
absorbs radio
frequency
(resonance
phenomena)
+1/2
LARMOR EQUATION
n =
g
2p
Bo
n= frequency of the radiation that comes, which will cause
the transition
g = giromagnetic ratio
different for each atom (H, C, N)
B0 = magnetic field
Magnetic Field
In organic compounds, hydrogen
atoms are surrounded by electrons
moving in the presence of a magnetic
field.
The movement of electrons around
the nuclei of hydrogen atoms in the
magnetic field result in Diamagnetic
Current
The area around the atomic nucleus
that is formed by electrons are
called Diamagnetic Shielding
B Induced
(opposed Bo)
Bo Applied
MEASUREMENT
 Liquid Sample
 Sample volume  0,5 mL
 Solvent
 1H NMR = deuterated solvent
CDCl3, CDOH3, Acetone-d6, Benzene-d6
Piridin-d5, DMSO-d6, D2O
13C NMR = CHCl , CHOH , Acetone, Benzene
3
3
Piridin, DMSO, H2O
 Sampel Amount = ≤ 50 mg
1H
NMR
INFORMATION FROM 1H NMR
1. Chemical Shift (, ppm), expressed as ppm (per
million)  functional group
2. Integration  number of proton
3. Multiplicity (s, d, t, q, qi, sext., hept.)  proton
relationship
4. Coupling Constant (J, Hz)  type of proton
relationship  stereochemistry or position of
proton
5. Proton Signal: 0-15 ppm
integration
multiplicity
Coupling
constante
standart
TMS
Chemical
shift
H group = amount & type of proton
ppm
HYDROGEN EQUIVALENT
Hydrogen Equivalent : Hydrogen that have a same chemical
environtment
- Compounds that have one hydrogen equivalent, producing
one peak of proton NMR
O
CH3 CCH3
ClCH 2 CH2 Cl
C
H3 C
Propan on e
(Ace ton e )
CH3
H3 C
1,2-Dich loro- C yclope n tan e
e th an e
C
CH3
2,3-Dime th yl2-bu ten e
- Compounds that have two/three hydrogen equivalent,
producing two/three peak of proton NMR
Cl
CH3 CHCl
1,1-Dichloroethane
(2 signals )
Cl
O
Cyclopentanone
(2 s ignals)
CH3
C C
H
H
(Z)-1-Ch loropropene
(3 signals)
Cyclohexen e
(3 signals)
How many proton signal??
O CH3
H3C C C CH3
CH3
O
CH2 CH2 O C CH3
CH3 CH2 CH2 NO2
Cl(CH2)3Cl
O
O
CH3CH2 O C (CH2)2 C O CH3
CHEMICAL SHIFT
NMR signal is not measured by resonance position, but based on
how far to shift from TMS, called CHEMICAL SHIFT
CH3
Has a highly protected proton and carbon
(appears on upfield region)
CH3
Si CH3
CH3
Tetrameth yls ilane (TMS)
PROTON CHEMICAL SHIFT
Proton chemical shift depends on the frequency of tool
used (shear difference for protons appear the same but
measured in different tools)
TMS
shift in Hz
downfield
n
chemical
shift
=

0
shift in Hz
=
spectrometer frequency in MHz
= ppm
Any specific protons in a molecule will always appear at
the same chemical shift (constant value)
PROTON CHEMICAL SHIFT
PROTON CHEMICAL SHIFT
C h e mi cal
Type of
Hydroge n
S h ift ()
( CH 3 ) 4 Si
0 (by defin i ti on )
RCH 3
0.8-1.0
RCH 2 R
1.2-1.4
R3 CH
1.4-1.7
R2 C= CRCH R2 1.6-2.6
RC CH
2.0-3.0
A rCH 3
2.2-2.5
A rCH 2 R
2.3-2.8
ROH
0.5-6.0
RCH 2 OH
3.4-4.0
RCH 2 OR
3.3-4.0
R2 NH
0.5-5.0
O
RCCH3
2.1-2.3
O
RCCH2 R
2.2-2.6
Type of
Hydroge n
O
RCOCH3
O
RCOCH2 R
RCH 2 I
RCH 2 Br
RCH 2 Cl
RCH 2 F
A rOH
R2 C= CH2
R2 C= CHR
A rH
O
RCH
O
RCOH
C h e mi cal
S h ift ()
3.7-3.9
4.1-4.7
3.1-3.3
3.4-3.6
3.6-3.8
4.4-4.5
4.5-4.7
4.6-5.0
5.0-5.7
6.5-8.5
9.5-10.1
10-13
PROTON CHEMICAL SHIFT
Factors affecting proton chemical shift :
1. Electronegatifity of the neighbour atoms
2. Hibridisation from the adjacent atoms
3. Diamagnetic Effect from the adjacent phi
bond
ELECTRONEGATIFITY
-
Cl
+
C
-
electronegative
H
+
•Chlorine pull electron density away
from carbon , caused electron density
around the proton.
•Chlorine caused proton to be
“deshields”
NMR CHART
Deshielding protons,
appears at low field
Shielding protons,
appears at high field
more deshielding
ELECTRONEGATIFITY
Chemical Shift of X on CH3X
CH3X
X
Electronegativity of X
Geseran Kimia d
Most
deshielded
CH3F
CH3OH
CH3Cl
F
O
Cl
4.0
3.5
4.26
3.40
CH3Br
CH3I
CH4
(CH3)4Si
Br
I
H
Si
3.1
2.8
2.5
2.1
1.8
3.05
2.68
2.16
0.23
0
TMS
ELECTRONEGATIFITY
"deshielding" effect increased with increasing number
of electronegative atoms
most
deshielded
CHCl3 CH2Cl2 CH3Cl
7.27 5.30
3.05 ppm
“deshielding” effect decrease with increasing proton
distance of electronegative atoms
most
deshielded -CH2-Br -CH2-CH2Br -CH2-CH2CH2Br
3.30
1.69
1.25
ppm
HIBRIDISATION
Type of Hydrogen
(R = alkyl)
N ame of
Hydrogen
Chemical
Sh ift ()
RCH3 , R2 CH2 , R3 CH
Alk yl
0.8 - 1.7
R2 C=C(R)CHR2
Allylic
1.6 - 2.6
RC CH
Acetylen ic
2.0 - 3.0
R2 C=CHR, R2 C=CH2
Vin ylic
4.6 - 5.7
RCHO
Ald ehydic
9.5-10.1
DIAMAGNETIC
• Magnetic Induction on phi bond causes the formation
of pi bonds
• The presence of phi bond (double bond) or phi system
will affect the chemical shift of nearby proton
• Accured on alkyne, alkene and benzene ring
- ALKYNE
- ALKENE
- BENZENE RING
SPLITTING SIGNAL
• On NMR spectrum, proton signals often do not appear
as a single peak (singlet), but appear as doublet,
triplet, quartet, and so on
• Spin-spin splitting on the H atom is due to the
interaction (coupling) with the neighboring H atom
• Spin-spin splitting followed the (n +1) RULES, if an
Atom H has n non-equivalent H atoms which are
neighbors, then the NMR spectrum of H atom signal
will experience a breakdown as a (n +1) peaks
(n+1) RULES
n = 1, the signal will
be splitted as (1+1)
peaks, doublet
n = 3, the signal will be
splitted as (3+1)
peaks, quartet
EXCEPTIONAL FOR (n+1) RULES
1)
2)
Equivalent protons due to symmetry effects are
usually not mutually spliting each other
X CH CH Y
X CH2 CH2 Y
no splitting if x=y
no splitting if x=y
Protons in the same group (tied to the same C) are
usually not mutually splitting each other
H
C H
H
H
or
C
H
EXEPTIONAL FOR (n+1) RULES
3)
N +1 rule applied to the protons in the aliphatic chain
(saturated) or cyclic saturated.
CH3
CH2CH2CH2CH2CH3
or
H
YES
YES
But it is not applied to the protons of the double
bond or benzene compounds
H
CH3
H
H
CH3
NO
NO
PASCAL TRIANGLE
• Splitting pattern similar
with PASCAL TRIANGLE
rule
SPLITTING PATTERN
X CH CH Y
CH3 CH
(x=y)
CH2 CH
X CH2 CH2 Y
(x=y)
CH3 CH2
CH3
CH
CH3
SPLITTING