CHEM60112B
Three and a half hours
The use of molecular models is allowed
A table of physical constants and conversion factors is attached
A periodic table is attached
THE UNIVERSITY OF MANCHESTER
PERSONALISED LEARNING UNIT
EXAMINATION PRACTICE PAPER
Answer ANY SIX questions.
Submit each question answer as a SEPARATE upload.
Each upload should be submitted as a file named as:
StudentId_CourseCode_QuestionNumber, e.g. 12345678_CHEM60112B_Q1
Each question is worth 25 marks
PTO
© University of Manchester, 2021
CHEM60112B
Page 2 of 19
1. CONTEMPORARY f-ELEMENT CHEMISTRY
Answer ALL parts.
(a) (i) Predict and explain the relative stabilities of complexes in the [AnCp3] (An = Th,
U, Np, Pu; Cp = C5H5–, cyclopentadienyl) series, with reference to oxidation states
and the relative energies of the 5f and 6d orbitals.
(4 marks)
(ii) Comment on the relative stabilities of UO22+ and UO2+ under anaerobic conditions.
Explain the chemical bonding that gives rise to this difference.
(4 marks)
(iii) How do uranyl(V) complexes typically decompose under anaerobic conditions?
Propose a chemical approach to prevent this decomposition pathway.
(2 marks)
(b) Examine the balanced equations and data given below which refer to the compounds
A-D and 1-2, then answer parts (i) to (iii).
A: Magnetometry revealed three unpaired 5f-electrons at uranium.
B: Absorption spectroscopy revealed a single strong absorption in the near-IR region.
Question 1 continued on next page
CHEM60112B
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Question 1 continued
(i) Identify complexes A and B, with reference to the data given.
(4 marks)
(ii) Complex B may decompose by several pathways. Name two potential
decomposition pathways. State the role the supporting ligands can have in supressing
decomposition.
(3 marks)
(iii) Predict and explain the two products that form from the reaction of complex 2 with
one equivalent of Me3NO. Give reasons why the formation of a single uranium containing
product from this reaction is thermodynamically favoured.
(3 marks)
(c) Examine the balanced equations and data given below which refer to the compounds
H, J and 3 (OAr = OC6H3But2-3,5). Draw H and J and describe the mechanisms by which
they form.
H: 13C NMR spectroscopy showed no incorporation of a 13C label.
J: 13C NMR spectroscopy showed incorporation of the 13C label.
(5 marks)
CHEM60112B
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2. CATALYTIC ASYMMETRIC SYNTHESIS
Answer ALL parts.
(a) (i) Suggest a method for the stereoselective synthesis of 2 from alcohol 1. Your
answer should include relevant mechanistic detail.
(5 marks)
(ii) Using the quadrant diagram for (R,R)-[Rh(DiPAMP)(COD)]BF4, shown below,
rationalise why hydrogenation of alkene 3 proceeds with modest
enantioselectivity (40% ee).
(5 marks)
Question 2 continued on next page
CHEM60112B
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Question 2 continued
(b) Using the conversion of 5 into 6 as an exemplar discuss what is meant by the term
kinetic resolution. Your answer should include reference to the concept of A-strain
and use of the Sharpless mnemonic. Comment on the chemoselectivity of this
reaction.
(10 marks)
(c) Outline a synthesis of the insect pheromone (+)-disparlure, 9, which utilises both
alcohol 7 and phosphonium salt 8 as key intermediates.
(5 marks)
CHEM60112B
Page 6 of 19
3. POLYMER MATERIALS
Answer ALL parts.
(a) (i) Describe how the x-ray scattering pattern of a glassy polymer differs from that of
a semi-crystalline polymer.
(3 marks)
(ii) Describe, with the aid of a sketch, how the specific volume changes on raising the
temperature for a glassy polymer and for a semi-crystalline polymer. Mark the
glass transition temperature, Tg, and the crystalline melting point, Tm, on your
sketch. Discuss the differences between a glass transition and melting.
(5 marks)
(iii) Describe, with the aid of a sketch, how the tensile stress-strain curve for a glassy
polymer differs from that for a semi-crystalline polymer.
(2 marks)
(b) (i) Explain how the tensile strength and the tensile modulus may be measured for a
polymer sample.
(4 marks)
(ii) The figure below shows the force-displacement curve obtained for a sample of
polystyrene in a tensile test. The gauge length was 75.00 mm. Within the gauge
length, the sample width was 10.23 mm and the thickness was 4.07 mm. Calculate
the tensile strength in MPa and the tensile modulus in GPa.
Question 3 continued on next page
CHEM60112B
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Question 3 continued
(6 marks)
(c) Discuss how the polymer chains are arranged in a single crystal of polyethylene.
(5 marks)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
Force / kN
Displacement / mm
CHEM60112B
Page 8 of 19
4. APPLIED OPTICAL SPECTROSCOPY
Answer ALL parts.
(a) Describe the components of a typical Fourier transform infrared spectrometer, and
explain the purpose of each part.
(10 marks)
(b) (i) Evaluate the viability of a thermal source at 6500 K for use in a measurement of
static fluorescence emission from a sample of an orange dye in solution.
(7 marks)
(ii) Is the source in part (i) appropriate for time-resolved fluorescence methods? If
not, suggest an alternative.
(3 marks)
(c) The vibrational sum-frequency spectrum of pyridine adsorbed on a Cu(110) surface
for (ppp) laser light is shown below. The peak at around 3080 cm–1 is an aromatic CH stretch. Deduce the orientation of the adsorbed pyridine.
(5 marks)
CHEM60112B
Page 9 of 19 PTO
5. MAIN GROUP REAGENTS IN SYNTHESIS
Answer ALL parts.
(a) Give mechanisms for BOTH of the transformations shown below, and explain the role
of the reagents containing phosphorus and silicon.
(10 marks)
(b) The following transformations involve the chemistry of compounds containing silicon,
sulfur, selenium or phosphorus. For BOTH of the transformations, give reagents and
mechanisms for the reactions involved.
(10 marks)
Question 5 continued on next page
CHEM60112B
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Question 5 continued
(c) Identify the intermediate A and product B in the following reaction sequence, and give
mechanisms for both steps in the sequence.
(5 marks)
CHEM60112B
Page 11 of 19 PTO
6. SURFACE ANALYSIS
Answer ALL parts.
(a) The following are scientific problems which can be investigated by applying an
appropriate surface science technique. For each problem, which surface science
technique is most appropriate to use, and why?
(i) A single-crystal metal surface is known to reconstruct upon exposure to oxygen
gas at elevated temperatures. How can the surface reconstruction be determined?
(3 marks)
(ii) We have attempted a new procedure to coat a piece of borosilicate glass with an
ultrathin layer of a polymer. How can we determine whether our coating
procedure has been successful?
(3 marks)
(iii) A single-crystal oxide surface dissociatively adsorbs water at defect sites on its
surface, to form hydroxyls. The defect sites are randomly arranged on the surface
at a low density (~1%). How can the coverage of hydroxyls on the oxide surface
be determined?
(2 marks)
(iv) A small molecule adsorbs on a single crystal surface with a desorption
temperature just below room temperature. How can we determine whether the
molecule is physisorbed or chemisorbed?
(2 marks)
Question 6 continued on next page
CHEM60112B
Page 12 of 19
Question 6 continued
(b) We consider a surface “contaminated”, and therefore unusable for experiments, when
the surface has greater than 10% coverage of adsorbates from the residual gas in the
chamber.
A Pt(100) crystal has just been cleaned by sputter/annealing in an ultrahigh vacuum
chamber with a base pressure of 8 10-11 mbar. Assuming that the residual gas in the
chamber is mainly hydrogen and has a sticking coefficient of 1, how much time do we
have available to perform our experiments before the surface is too contaminated?
The surface unit cell of Pt(100) has a lattice constant of 2.8 Å.
(10 marks)
(c) The three LEED patterns below are from an experiment where graphene was grown
on a single crystal of copper. Pattern A is the clean surface before graphene growth,
pattern B is after graphene growth at 800 C and pattern C is after graphene growth at
900 C.
(i) What is the Miller index of the copper surface?
(1 mark)
Question 6 continued on next page
CHEM60112B
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Question 6 continued
(ii) What does the ring that appears in pattern B tell you about the graphene grown on
this crystal?
(3 marks)
(iii) In pattern C the ring looks different to pattern B. What does this tell you about
graphene grown at higher temperatures?
(1 mark)
CHEM60112B
Page 14 of 19
7. INDUSTRIAL SEPARATIONS
Answer ALL parts.
(a) (i) Give an overview of basic techniques that may be used to separate a feed mixture
into two streams that differ in their composition.
(5 marks)
(ii) Outline two techniques that may be used for separation of an ethanol/water
mixture, indicating the advantages and disadvantages of each.
(5 marks)
(b) A gas separation process for the capture of CO2 from a flue gas requires a membrane
with a CO2 permeance of at least 1,000 gas permeation units (GPU) and a CO2/N2
selectivity greater than 20. The table below gives values of CO2 and N2 permeability
in Barrer units for four high free volume, glassy polymers. For each polymer calculate
the CO2 permeance in GPU for membrane thicknesses of 2 m and 5 m, and calculate
the CO2/N2 selectivity. Discuss the suitability of each of these polymers for CO2
capture membranes.
| Polymer | CO2 permeability / Barrer | N2 permeability / Barrer |
| PIM-1 | 2300 | 92 |
| PIM-7 | 1100 | 42 |
| KAUST-PI-1 | 2390 | 107 |
| PTMSP | 27000 | 6600 |
AssignmentTutorOnline
(10 marks)
Question 7 continued on next page
CHEM60112B
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Question 7 continued
(c) Compare the pore-flow and solution-diffusion models of transport though a membrane,
indicating the types of membrane separation for which each model is appropriate.
(5 marks)
CHEM60112B
Page 16 of 19
8. SOLID STATE NMR: PRINCIPLES AND APPLICATIONS
Answer ALL parts.
(a) Discuss in detail, giving examples, the theory behind the use of magic-angle spinning,
cross-polarisation, and heteronuclear decoupling for recording high quality NMR
spectra in the solid state.
(10 marks)
(b) The figure below shows the 29Si solid-state NMR spectrum for a series of four zeolite
Y samples and the 27Al solid-state NMR spectrum for one of these samples. (The
number above each peak is the relative integral).
Discuss the structural information that can be obtained from these spectra and derive,
with full reasoning, an equation for the Si:Al ratio of a sample, and comment on the *
in the 27Al spectrum.
(10 marks)
Question 8 continued on next page
CHEM60112B
Page 17 of 19 PTO
Question 8 continued
(c) Determine the framework Si/Al ratio for each of the four samples in the figure in part
(b), and comment why this might be different from a full chemical analysis.
(5 marks)
End of Paper
Page 18 of 19
PHYSICAL CONSTANTS AND CONVERSION FACTORS
PHYSICAL CONSTANTS
| Gas constant Avogadro constant Boltzmann constant Planck constant |
R L, NA k, kB h |
8.314 6.022 1023 1.381 10–23 6.626 10–34 1.055 10–34 |
J K–1 mol–1
mol–1
J K–1
J s
h– = h
2p
J s
Speed of light c 2.998 108 m s–1
Mass of electron m
e 9.109 10–31 kg
Mass of proton mp 1.673 10–27 kg
Unified atomic mass unit u, mu 1.661 10–27 kg
Charge on the electron –e
| –1.602 10–19 9.649 104 |
C C mol–1 |
Faraday constant F RT/F at 298 K 0.0257 V
Vacuum permittivity 0 8.854 10–12 C2 m–1 J–1
0 1.113 10–10 C2 m–1 J–1
| Rydberg wavenumber constant for hydrogen |
RH |
109737 cm–1
CONVERSION FACTORS
ln x = 2.303 log10 x
0 °C = 273.15 K
1 atmosphere (atm) = 760 Torr (mm of Hg) = 1.013 105 Pa
1 bar = 105 Pa
1 eV = 1.602 10–19 J
1 Å = 10–10 m
Page 19 of 19
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 |
| 1 H 1.0079 |
2 He 4.0026 |
||||||||||||||||
| 3 Li 6.941 |
4 Be 9.0122 |
5 B 10.811 |
6 C 12.011 |
7 N 14.007 |
8 O 15.999 |
9 F 18.998 |
10 Ne 20.180 |
||||||||||
| 11 Na 22.990 |
12 Mg 24.305 |
13 Al 26.982 |
14 Si 28.086 |
15 P 30.974 |
16 S 32.065 |
17 Cl 35.453 |
18 Ar 39.948 |
||||||||||
| 19 K 39.098 |
20 Ca 40.078 |
21 Sc 44.956 |
22 Ti 47.867 |
23 V 50.942 |
24 Cr 51.996 |
25 Mn 54.938 |
26 Fe 55.845 |
27 Co 58.933 |
28 Ni 58.693 |
29 Cu 63.546 |
30 Zn 65.409 |
31 Ga 69.723 |
32 Ge 72.64 |
33 As 74.922 |
34 Se 78.96 |
35 Br 79.904 |
36 Kr 83.798 |
| 37 Rb 85.468 |
38 Sr 87.62 |
39 Y 88.906 |
40 Zr 91.224 |
41 Nb 92.906 |
42 Mo 95.94 |
43 Tc (98) |
44 Ru 101.07 |
45 Rh 102.91 |
46 Pd 106.42 |
47 Ag 107.87 |
48 Cd 112.41 |
49 In 114.82 |
50 Sn 118.71 |
51 Sb 121.76 |
52 Te 127.60 |
53 I 126.90 |
54 Xe 131.29 |
| 55 Cs 132.91 |
56 Ba 137.33 |
57-71 | 72 Hf 178.49 |
73 Ta 180.95 |
74 W 183.84 |
75 Re 186.21 |
76 Os 190.23 |
77 Ir 192.22 |
78 Pt 195.08 |
79 Au 196.97 |
80 Hg 200.59 |
81 Tl 204.38 |
82 Pb 207.2 |
83 Bi 208.98 |
84 Po (209) |
85 At (210) |
86 Rn (222) |
| 87 Fr (223) |
88 Ra (226) |
89- 103 |
104 Rf (261) |
105 Db (262) |
106 Sg (266) |
107 Bh (264) |
108 Hs (277) |
109 Mt (268) |
110 Ds (271) |
111 Rg (272) |
112 Cn (285) |
113 Nh (286) |
114 Fl (289) |
115 Mc (290) |
116 Lv (293) |
117 Ts (294) |
118 Og (294) |
| 57 La 138.91 |
58 Ce 140.12 |
59 Pr 140.91 |
60 Nd 144.24 |
61 Pm (145) |
62 Sm 150.36 |
63 Eu 151.96 |
64 Gd 157.25 |
65 Tb 158.93 |
66 Dy 162.50 |
67 Ho 164.93 |
68 Er 167.26 |
69 Tm 168.93 |
70 Yb 173.04 |
71 Lu 174.97 |
|||
| 89 Ac (227) |
90 Th 232.04 |
91 Pa 231.04 |
92 U 238.03 |
93 Np (237) |
94 Pu (244) |
95 Am (243) |
96 Cm (247) |
97 Bk (247) |
98 Cf (251) |
99 Es (252) |
100 Fm (257) |
101 Md (258) |
102 No (259) |
103 Lr (262) |
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