H
H
H
C
C
H
H
H
H
H
H
H
C
C
H
H
H
O
H
C
C
C
H
H H
C H H C H H
O
H
OH C C
C
H
H OH C H
H
H
H
Q1
Which molecule has an odd number of peaks in its A
B
O
S
13
C NMR spectrum? C
D
O
O O
MgCl
Q2 A structural isomer of C5H11OH has a significant peak in its mass spectrum with an Its 13C NMR spectrum shows four different peaks. What is the isomer?
Q3
A
3-methylbutan-1-ol
B
3-methylbutan-2-ol
C
pentan-1-ol
D
pentan-2-ol
The diagram shows the
13
C NMR spectrum of an alcohol of formula C4H10O.
200 180 160 140 120 100
80
60
δ ppm
What is the alcohol? A
butan-1-ol
B
butan-2-ol
C
2-methylpropan-2-ol
D
2-methylpropan-1-ol
40
20
/ value of 31.
m z
0
Q4
Dioxins can be formed during the combustion of chlorine-containing compounds in waste incinerators. Dioxins are very unreactive compounds and therefore remain in the environment and enter the food chain. Many dioxins are polychlorinated compounds such as tetrachlorodibenzodioxin (TCDD) shown below. C
O
C
C
O
C
TCDD can also be analysed using
13
C n.m.r.
Deduce the number of peaks in the 13C n.m.r. spectrum of TCDD. [1]
H H H
H
C H
C
H
Si H
C
H C
H
H Si(CH3)4
H
H
H C
H
H
O C
H O
H
ethanoic acid
Q5
The
13
H
H
C
C
H
H
O C
H O
H
H
H
H
C
C
C
H
H
H
O
C NMR spectrum of a compound with formula C 4H8O2 shows peaks at 15 ppm, 20 ppm,
What is the structure of the compound?
HOCH2CHCHCH2OH
C
CH3COOCH2CH3 H
H B
C
butanoic acid
propanoic acid
60 ppm and 175 ppm.
A
O
HCOOCH(CH3)2
D
HO
C
C
OH
H
C
C
H
H
H
H
Q6
O
Shikimic acid, right, occurs naturally in star anise.
7
HO Using the numbers on the diagram of shikimic acid’s structure, indicate (by putting numbers in the boxes) which carbon atoms in the molecule are responsible for each signal in its
1 6
HO
13
C NMR spectrum.
5
2
OH
3
4
OH
The precise order of carbons within the group of two and the group of three are not required.
200
180
160
140
120
100 δ / ppm
80
60
40
20
0 [3]
Q7
Atenolol is an example of the type of medicine called a beta blocker. These medicines are used to lower blood pressure by slowing the heart rate. The structure of atenolol is shown below. OH H2N
C
CH2
O
CH2
CH
CH2
H
CH3
N
CH
q
O
Q7 (a)
The
13
CH3
C n.m.r. spectrum of atenolol was recorded.
Use the structure of atenolol given to deduce the total number of peaks in the 13
C n.m.r. spectrum of atenolol. [1]
Q7 (b)
Part of the
13
C n.m.r. spectrum of atenolol is shown on the right.
Use this spectrum to answer the questions which follow. Give the formula of the compound that is used as a standard and produces the peak at
δ
= 0 ppm in the spectrum. [1]
Q7 (c)
One of the peaks in the
13
C n.m.r. spectrum is produced by
the CH3 group labelled q in the structure of atenolol. Identify this peak in the spectrum by stating its
δ
value. [1]
100
80
60
40
δ / ppm
Q7 (d)
There are three CH2 groups in the structure of atenolol. One of these CH 2 groups produces the peak at
δ
= 71 in the
13
C n.m.r. spectrum above.
Draw a circle around this CH 2 group in the structure of atenolol shown below. OH H2N
C O
CH2
O
CH2
CH
CH2
H
CH3
N
CH
CH3 [1]
20
0
H
H
H
H
H
C
C
H
H
H
H
H
C
C
H
H
H
O
H
C
C
C
H
O
H
H
H
Q8
Many aromatic nitro compounds are used as explosives. One of the most famous is 2-methyl-1,3,5-trinitrobenzene, originally called trinitrotoluene or TNT, shown below . CH3 O2N
NO2
NO2
Q8 (a) Deduce the number of peaks in the
13
C n.m.r. spectrum of TNT. [1]
Q8 (b)
Deduce the number of peaks in the 1H n.m.r. spectrum of TNT. [1]
Q8 (c)
Using the molecular formula (C 7H5N3O6), write an equation for the decomposition reaction that occurs on the detonation of TNT. In this reaction equal numbers of moles of carbon and carbon monoxide are formed together with water and nitrogen. [1]
Q9
Imipramine has been prescribed as an antidepressant. The structure of imipramine is shown below.
H 2C
CH2
N H 2C CH2 H 2C N
CH3
H 3C Q9 (a)
Deduce the number of peaks in the
13
C n.m.r. spectrum of imipramine . [1]
Q9 (b)
Deduce the number of peaks in the 1H n.m.r. spectrum of imipramine . [1]
1
3
absorption of energy
2
11
10
9
8
7
6
5
4
3
2
1
0
δ / ppm
H
H
H
C
C
H
H
O
H
3
1 2
H
H
H
C
C
H
H
O
H
H
H
H
H
C
C
C
H
H
H
H
H
H
H
H
H
C
C
C
C
H
H
H
H
H
Q10
Atenolol is an example of the type of medicine called a beta blocker. These medicines are used to lower blood pressure by slowing the heart rate. The structure of atenolol is shown below. OH C
H2N
O
CH2
O
CH2
CH
CH2
H
CH3
N
CH
CH3
p
The 1H n.m.r. spectrum of atenolol was recorded. One of the peaks in the 1H n.m.r. spectrum is produced by the CH2 group labelled p in the structure of atenolol. Suggest a range of Range of
δ
δ
values for this peak. Name the splitting pattern of this peak.
values
Name of splitting pattern
Q11
[2]
The 1H NMR spectrum of butanone is shown below. B
C D A
Without considering chemical shift data, which peak is produced by Q11 (a)
the red hydrogens;
[1]
Q11 (b)
the blue hydrogens;
[1]
Q11 (c)
the green hydrogens?
[1]
Q12
The 1H NMR spectrum of triethylamine is shown below.
B
C
A
Without considering chemical shift data, which peak is produced by Q12 (a)
the red hydrogens;
[1]
Q12 (b)
the blue hydrogens?
[1]
Q13
Haloalkanes have been used as aerosol propellants and refrigerants but are now largely banned due to the damage they cause to the ozone layer. Halon 1211 was once commonly used in fire extinguishers (now only found in fighter jets) and ‘Halothane’ is an inhalational general anaesthetic. Further examples of haloalkanes are given in the table below.
Common name
Structural
Number of different
formula
fluorine environments
A
CFC-113
Cl2FC-CClF2
B
CFC-113a
Cl3C-CF3
C
HFC-134a
F3C-CH2F
D
CFC-11 (Freon-11, R-11)
CCl3F
E
CFC-12 (Freon-12, R-12)
CCl2F2
F
CFC-13
CClF3
G
Halon 1211
CBrClF2
NMR spectroscopy is a technique which reveals the number of different environments of certain nuclei in a molecule. NMR active nuclei such as 1H, 13C and 19F are routinely studied. Q13 (a)
Complete the table above indicating the number of different fluorine environments for each of the compounds A –G
Q13 (b)
.
[3]
The anaesthetic Halothane has the formula C 2HBrClF3 and shows one signal in its 19
F NMR spectrum. Draw the two possible three-dimensional structures for Halothane.
[2]
Q13 (c)
The intensity of a signal in a 1H or 19F NMR spectrum is proportional to the number of nuclei in that particular environment. For each compound with more than one signal in its 19F NMR spectrum, indicate in the appropriate column of the table the expected intensity ratio.
[2]
Q13 (d)
NMR spectra are complicated by coupling between nuclei. If an NMR-active nucleus is within three bonds of another similar nucleus which is in a different chemical environment, its signal will be split into a number of peaks instead of appearing as a single peak. If a nucleus couples to n NMR-active nuclei, its signal will split into a total of (n + 1) peaks. The 19F NMR spectrum of one of the haloalkanes from the table is shown below. Draw the structure of the haloalkane and indicate with an arrow which fluorines give rise the signals X and Y.
[2]
Q14
The 1H NMR spectrum for ibuprofen is shown below.
On the structure of ibuprofen below, mark the protons responsible for the peaks C, D, E and F on
A, B,
the spectrum. The integrals and expansions for each peak are shown on the spectrum.
O CH3
OH CH3
H3C [6]
H R
C H
H O
1H
+
O 2H
2H
→
R
C H
O
2H
+
O 1H
2H
Q15
Below are the structures of a pair of isomers. H
H C H
H C H
O
H H
C C
H
O
C H
C
H
H
C
O
C
C
H
O
H C H
H
isomer 1
Q15 (a)
H
H
H
isomer 2
Give the molecular formula of these isomers. [1]
Q15 (b)
What type of isomerism is shown by these two isomers? [1]
Q15 (c)
Isomer 1 is named 2-phenylethyl propanoate. Give the name of isomer 2. [1]
Q15 (d)
The 1H NMR spectrum of one of the isomers is shown in below.
integration
10
3
5
2
2
2
5 δ / ppm
0
Explain which of the two isomers corresponds to the 1H NMR spectrum. You should refer to the splitting patterns and integration values of
all the
answer. Note that the phenyl group protons appear as a single peak.
peaks in your
[6]
Q16
An unknown compound T consists of carbon, hydrogen and oxygen atoms only. The 1H NMR spectrum of T and the 13C NMR spectrum of T are both shown below. Deduce the structural formula of the compound T and explain the form of the spectra. This should include the identification of the atoms or groups of atoms responsible for each signal.
11
10
9
8
7
6 1
200
180
160
140
5
4
H NMR spectrum of
120 13
100
3
2
1
T
80
C NMR spectrum of
60 T
40
20
0 δ / ppm
0 δ / ppm
[7]
Q17
A, B and C are
three structural isomers of molecular formula C6H10O. They are all cyclic.
Isomers A and B have strong infra-red absorptions, C has
A at
1720 cm –1 and
B at
1780 cm –1;
an absorption at 1650 cm –1 and a broad absorption between 3230 and 3550 cm –1.
In the proton n.m.r. spectrum, A has three peaks (signals) with areas in the ratio 2:2:1 whereas B has two peaks in the ratio 3:2; C has 4 peaks with areas in the ratio 1:2:3:4.
C reacts
readily with bromine water; A and B do not.
None of the three isomers can be oxidised by acidified potassium dichromate(VI).
Suggest structures for A, B and C, explaining your reasoning.
[10]
