how many peaks in the 13c nmr spectra? - chemistry · how many peaks in the 13c nmr spectra? oh ohf...
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How many peaks in the 13C NMR spectra?
OH OHFOHFF
2 3 4 3
ClFHOClFCl ClClCl
6 4 2
Which compound matches this 13C NMR spectrum?BrBrBr
BrBrBr
BrBrBr
BrBrBr
OOH
AB
C
O
A
BC
Br B
CA
Rank the labeled C’s of each compound in order of increasingchemical shift?
B ~ 33ppm
C ~ 35ppm
A ~ 115ppm
A ~ 8ppm
B ~ 37ppm
C ~ 210ppm
C ~ 9ppm
B ~ 30ppm
A ~ 177ppm
NO
O
OH
NO
A compound has a 13C NMR spectrum with three peaks and the IRspectrum below, choose the correct compound.
Information gained from a 1H NMR Spectrum
• Number of Signals
• Position of Signals
• Intensity of Signals
• Spin-Spin Splitting of Signals
How many different types of protons are in each compound?
H3COCH3
HAHA
1 type
H3CH2CCl
HA
HB
2 types
H3CH2COCH3
HA
HB
HC
3 types
H3CCHH3CCH2H2CCH3
HA
HA
HB
HC
HD
HE
5 types
Determining the number of different protons in compoundswith π bonds.
ClClHH cis to Cl
cis to Cl
1 type
ClBrHH cis to Cl
cis to Cl
2 types
ClHHHcis to Cl
cis to H
3 types
Determining the number of different protons in compounds withrings..
HHHHHH
All H’s areequivalent, 1 type
HHHHClHcis to Cl
cis to H3 types
HHHHCH3CH3
Protons onmethylsareequivalent
Each ofthese is cisto amethyl 2 types
If two protons attached to the same carbon can be replacedseparately with a common group such as a Z group which resultsin creating two molecules that are enantiomers to one another, inother words they are non-superimposible mirror images, theseprotons are called enantiotopic protons.
Enantiotopic Protons
If two protons attached to the same carbon can be replacedseparately with a common group such as a Z group which results increating two molecules that are diastereomers, these protons wouldbe diastereotopic protons. Such protons will generate nmr signals atslightly different chemical shifts.
Diasterotopic Protons
OOOOH
OO HOOH
Spin-SpinCoupling
When determining the spin-spin coupling, look at the number ofprotons on the adjacent carbon. For the methyl group, look at themethylene group. There are 2 protons, so using the N+1 rule tells usthat the peak should be a triplet in a 1:2:1 ratio.
For the methylene group, look at the methyl group. There are 3protons, so using the N+1 rule tells us that the peak should be aquartet in a 1:3:3:1 ratio.
Protons attached via a double bond show a unique splittingpattern., a doublet of doublets.
O
HO
⇑
Hc
⇑
Ha
⇑
HbN+1=4+1=5
OOH
O
OH