C8953
NMR structural analysis - seminar
1D 13C-NMR
Kateˇrina Peterková, Aleš Novotný
423977@mail.muni.cz
March 13, 2019
Control of 1D 1
H NMR spectrum of cartilagineal
Control of 1D 1
H NMR spectrum - cartilagineal
Notes:
highest shift - H-2 - proton of aldehydic
group, splitted to doublet with J = 2 Hz
(small value, interacting partner is
relatively far away)
the same J = 2 Hz belongs to doublet of
doublets of doublets around 6.5 ppm,
other Js: J = 1 Hz and J = 15.5 Hz three
J-constants - three partners - H-3
large J-value 15.5 Hz suggests near
neighbor - other signal with the same
constant is doublet of doublets around 7
ppm - H-4
last constant of multiplet at 6.5 ppm - J
= 1 Hz - partner distant from H-3: either
H-1 or H-5, the same J- constant
belongs to doublet of doublets at 4,5
ppm - two constants, two partners which
is not the case for H-1 - therefore signal
at 4,5 ppm belongs to H-5
just for check: both multiplets H-4 and H-5 are coupled with H-3 and with each other as well (J = 8.5 Hz)
the only singlet in the spectrum is isolated H-1
last unasigned doublet of doublets (6,1 ppm) must be H-6 because it is the only proton from the trio H-6, H-7, H-8 with two
unequivalent neighbors - larger coupling comes from interaction with H-8 in trans position, smaller coupling comes from
interaction with cis oriented H-7
signal of the methyl group is not present in this spectrum
1
H vs 13
C NMR
1
H 13
C
Spin number 1
H: s=1
2
× 2
H: s=1 13
C: s=1
2
× 12
C: s=0
Abundance [%] 99.98 1.1
Gyromagnetic ratio [107
rad.T−1
.s−1
] 26.8 6.7
Chemical shift range [ppm] 0 - 15 0 - 200
Nuclear shielding σdia σdia + σpara
Integration of signals ×
T1 relaxation [s] 1-20 1-40
Homonuclear J-interaction ×
H↔C J-interaction (∼ 100-250 Hz) carbon satellites (n + 1) splitting × decoupling
1
H vs 13
C NMR
1
H 13
C
Spin number 1
H: s=1
2
× 2
H: s=1 13
C: s=1
2
× 12
C: s=0
Abundance [%] 99.98 1.1
Gyromagnetic ratio [107
rad.T−1
.s−1
] 26.8 6.7
Chemical shift range [ppm] 0 - 15 0 - 200
Nuclear shielding σdia σdia + σpara
Integration of signals ×
T1 relaxation [s] 1-20 1-40
Homonuclear J-interaction ×
H↔C J-interaction (∼ 100-250 Hz) carbon satellites (n + 1) splitting × decoupling
1
H-13
Cα 1
H-13
Cβ
1
H-12
C
ωC-0.51
JHCωC+0.51
JHC
1
JHC
1
JHC
1D 1
H NMR
1D 13
C NMR
1
Hβ-13
C1
Hα-13
C
1
H decoupled
Important regions of 13
C chemical shifts
Aldehydes RCH=O
Ketones R1R2C=O
Carboxylic acids R-CO2H
Esters R-CO2R'
Amines R-CONR2'
C-NO2
C-F C-Cl
C-Br
C-I
C-H Saturated Hydrocarbons
C-NH2
C-OH C-SR
C-OR C-Ar
C-SO2 R
C-CO R
C-C=C
C CR
RC N
Heteroaromatics
Aromatics
R2C=CH2
RHC=CHR
R2C=CH2
200 150 100 50 0.0
ppm(δ)
Alkenes
Alkynes
1
JCH depends on the bond order ( hybridization ⇔
s-character )
-C-H 1JCH ≈ 125 Hz
=C-H 1JCH ≈ 160 Hz
≡C-H 1JCH ≈ 250 Hz
X-C-H
X = N, O, S, F, Cl, . . . 1
JCH ⇑
X = Li, Mg, . . . 1
JCH ⇓
2
JCH < 0 or close to zero (<3 Hz)
often not observable
in 1D 13
C H-C interaction suppressed by DECOUPLING
⇒ simplification of spectra (splitting removed, sensitivity)
saturation of 1H energy levels during decoupling enhances
relatively intensity of 13C signals because of heteronuclear
nOe ⇒ quaternary carbons usually less intensive.
Values of chemical shift of important solvents
Abbr. Formula 1
H 13
C
ACN CH3CN 1.9 118
Benzene C6H6 7.2 128
CHCl3 7.2 77
DCM CH2Cl2 5.3 54
DMF (CH3)2NCHO 2.9, 8.0 32, 163
DMSO (CH3)2SO 2.5 40
MeOH CH3OH 3.3, 4.8 49
Water H2O 4.8 EXPLAIN
effect of solvent on the position of residual 1H water
signal:
CHCl3 - 1.6, ACN - 2.1, DMSO - 3.3, MeOH - 4.9
How many 13
C signal would you expect in the NMR
spectrum?
Ru
N
N
N
N
Cl Cl
Cl
S CH3
CH3
O
N+
-
N
H
How many 13
C signal would you expect in the NMR
spectrum? 7
Ru
N
N
N
N
Cl Cl
Cl
S CH3
CH3
O
N+
-
N
H
1D 13
C-NMR 1, bottom without CPD
1D 13
C-NMR 1, bottom without CPD
Notes:
numbers at top of peaks
refers to values JHC
constants
C1+C7 connected to
electronegative groups
(C1 quaternary)
C2 ipso aromatic, C4+C6
shielded by M+ of OH
C5+C4 NOE-enhanced in
bit larger extend by close
H
C9→C12: decaying effect
of N8
1D 13
C-NMR 2
ZOOM of coupled region
of most deshielded signals
coupled spectrum
spectrum with decoupling
1D 13
C-NMR 2
Notes:
C7 carbonyl, C1 attached
to N
C3/5 deshielded by MCO,
C2/6 shielded by M+
of NH2
C4 last quaternary
aromatic signal (most
isolated from H nuclei)
C9 effect of esteric group,
? C10 affected by NH
exchange
C12/C14 + C13/C15
decaying effect of N+
1D 13
C-NMR 3, b - zoom of right region, a - full decoupled spectrum
1D 13
C-NMR 3, b - zoom of right region, a - full decoupled spectrum
Notes:
C3/C4 quaternary
aromatic deshielded by O,
Cβ quaternary coupled by
CH3 and CαH
Cα deshielded by NO2
C1 last quaternary
aromatic signal
C2/C6 coupled mutually
and with Cα, C5 isolated
(contraintuitive)
quartets OMe, Cγ
1D 13
C-NMR 4, consider equilibrium minor-major form
Which form dominates and why?
1D 13
C-NMR 4, consider equilibrium minor-major form
Which form dominates and why?
Next topic
Vector Model + 13C APT experiment