CONTEMPORARY f-ELEMENT CHEMISTRY | My Assignment Tutor

CHEM60112BThree and a half hoursThe use of molecular models is allowedA table of physical constants and conversion factors is attachedA periodic table is attachedTHE UNIVERSITY OF MANCHESTERPERSONALISED LEARNING UNITEXAMINATION PRACTICE PAPERAnswer 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_Q1Each question is worth 25 marksPTO© University of Manchester, 2021CHEM60112BPage 2 of 191. CONTEMPORARY f-ELEMENT CHEMISTRYAnswer 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 statesand 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 compoundsA-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 pageCHEM60112BPage 3 of 19 PTOQuestion 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 potentialdecomposition pathways. State the role the supporting ligands can have in supressingdecomposition.(3 marks)(iii) Predict and explain the two products that form from the reaction of complex 2 withone equivalent of Me3NO. Give reasons why the formation of a single uranium containingproduct from this reaction is thermodynamically favoured.(3 marks)(c) Examine the balanced equations and data given below which refer to the compoundsH, J and 3 (OAr = OC6H3But2-3,5). Draw H and J and describe the mechanisms by whichthey form.H: 13C NMR spectroscopy showed no incorporation of a 13C label.J: 13C NMR spectroscopy showed incorporation of the 13C label.(5 marks)CHEM60112BPage 4 of 192. CATALYTIC ASYMMETRIC SYNTHESISAnswer ALL parts.(a) (i) Suggest a method for the stereoselective synthesis of 2 from alcohol 1. Youranswer 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 modestenantioselectivity (40% ee).(5 marks)Question 2 continued on next pageCHEM60112BPage 5 of 19 PTOQuestion 2 continued(b) Using the conversion of 5 into 6 as an exemplar discuss what is meant by the termkinetic resolution. Your answer should include reference to the concept of A-strainand use of the Sharpless mnemonic. Comment on the chemoselectivity of thisreaction.(10 marks)(c) Outline a synthesis of the insect pheromone (+)-disparlure, 9, which utilises bothalcohol 7 and phosphonium salt 8 as key intermediates.(5 marks)CHEM60112BPage 6 of 193. POLYMER MATERIALSAnswer ALL parts.(a) (i) Describe how the x-ray scattering pattern of a glassy polymer differs from that ofa semi-crystalline polymer.(3 marks)(ii) Describe, with the aid of a sketch, how the specific volume changes on raising thetemperature for a glassy polymer and for a semi-crystalline polymer. Mark theglass transition temperature, Tg, and the crystalline melting point, Tm, on yoursketch. 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 glassypolymer 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 apolymer sample.(4 marks)(ii) The figure below shows the force-displacement curve obtained for a sample ofpolystyrene in a tensile test. The gauge length was 75.00 mm. Within the gaugelength, the sample width was 10.23 mm and the thickness was 4.07 mm. Calculatethe tensile strength in MPa and the tensile modulus in GPa.Question 3 continued on next pageCHEM60112BPage 7 of 19 PTOQuestion 3 continued(6 marks)(c) Discuss how the polymer chains are arranged in a single crystal of polyethylene.(5 marks)0.00.20.40.60.81.01.21.41.60.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2Force / kNDisplacement / mmCHEM60112BPage 8 of 194. APPLIED OPTICAL SPECTROSCOPYAnswer ALL parts.(a) Describe the components of a typical Fourier transform infrared spectrometer, andexplain the purpose of each part.(10 marks)(b) (i) Evaluate the viability of a thermal source at 6500 K for use in a measurement ofstatic 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? Ifnot, suggest an alternative.(3 marks)(c) The vibrational sum-frequency spectrum of pyridine adsorbed on a Cu(110) surfacefor (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)CHEM60112BPage 9 of 19 PTO5. MAIN GROUP REAGENTS IN SYNTHESISAnswer ALL parts.(a) Give mechanisms for BOTH of the transformations shown below, and explain the roleof 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 andmechanisms for the reactions involved.(10 marks)Question 5 continued on next pageCHEM60112BPage 10 of 19Question 5 continued(c) Identify the intermediate A and product B in the following reaction sequence, and givemechanisms for both steps in the sequence.(5 marks)CHEM60112BPage 11 of 19 PTO6. SURFACE ANALYSISAnswer ALL parts.(a) The following are scientific problems which can be investigated by applying anappropriate surface science technique. For each problem, which surface sciencetechnique is most appropriate to use, and why?(i) A single-crystal metal surface is known to reconstruct upon exposure to oxygengas 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 anultrathin layer of a polymer. How can we determine whether our coatingprocedure has been successful?(3 marks)(iii) A single-crystal oxide surface dissociatively adsorbs water at defect sites on itssurface, to form hydroxyls. The defect sites are randomly arranged on the surfaceat a low density (~1%). How can the coverage of hydroxyls on the oxide surfacebe determined?(2 marks)(iv) A small molecule adsorbs on a single crystal surface with a desorptiontemperature just below room temperature. How can we determine whether themolecule is physisorbed or chemisorbed?(2 marks)Question 6 continued on next pageCHEM60112BPage 12 of 19Question 6 continued(b) We consider a surface “contaminated”, and therefore unusable for experiments, whenthe surface has greater than 10% coverage of adsorbates from the residual gas in thechamber.A Pt(100) crystal has just been cleaned by sputter/annealing in an ultrahigh vacuumchamber with a base pressure of 8  10-11 mbar. Assuming that the residual gas in thechamber is mainly hydrogen and has a sticking coefficient of 1, how much time do wehave 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 grownon 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 at900 C.(i) What is the Miller index of the copper surface?(1 mark)Question 6 continued on next pageCHEM60112BPage 13 of 19 PTOQuestion 6 continued(ii) What does the ring that appears in pattern B tell you about the graphene grown onthis crystal?(3 marks)(iii) In pattern C the ring looks different to pattern B. What does this tell you aboutgraphene grown at higher temperatures?(1 mark)CHEM60112BPage 14 of 197. INDUSTRIAL SEPARATIONSAnswer ALL parts.(a) (i) Give an overview of basic techniques that may be used to separate a feed mixtureinto two streams that differ in their composition.(5 marks)(ii) Outline two techniques that may be used for separation of an ethanol/watermixture, 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 membranewith a CO2 permeance of at least 1,000 gas permeation units (GPU) and a CO2/N2selectivity greater than 20. The table below gives values of CO2 and N2 permeabilityin Barrer units for four high free volume, glassy polymers. For each polymer calculatethe CO2 permeance in GPU for membrane thicknesses of 2 m and 5 m, and calculatethe CO2/N2 selectivity. Discuss the suitability of each of these polymers for CO2capture membranes. PolymerCO2 permeability / BarrerN2 permeability / BarrerPIM-1230092PIM-7110042KAUST-PI-12390107PTMSP270006600 (10 marks)Question 7 continued on next pageCHEM60112BPage 15 of 19 PTOQuestion 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)CHEM60112BPage 16 of 198. SOLID STATE NMR: PRINCIPLES AND APPLICATIONSAnswer 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 NMRspectra in the solid state.(10 marks)(b) The figure below shows the 29Si solid-state NMR spectrum for a series of four zeoliteY samples and the 27Al solid-state NMR spectrum for one of these samples. (Thenumber 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 pageCHEM60112BPage 17 of 19 PTOQuestion 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 PaperPage 18 of 19PHYSICAL CONSTANTS AND CONVERSION FACTORSPHYSICAL CONSTANTS Gas constantAvogadro constantBoltzmann constantPlanck constantRL, NAk, kBh8.3146.022  10231.381  10–236.626  10–341.055  10–34 J K–1 mol–1mol–1J K–1J sh– = h2pJ sSpeed of light c 2.998  108 m s–1Mass of electron me 9.109  10–31 kgMass of proton mp 1.673  10–27 kgUnified atomic mass unit u, mu 1.661  10–27–1.602  10–19kgC Charge on the electron –e Faraday constant F 9.649  104 C mol–1RT/F at 298 K 0.0257 VVacuum permittivity 0 8.854  10–12 C2 m–1 J–10 1.113  10–10 C2 m–1 J–1 Rydberg wavenumberconstant for hydrogenRH 109737 cm–1CONVERSION FACTORSln x = 2.303 log10 x0 °C = 273.15 K1 atmosphere (atm) = 760 Torr (mm of Hg) = 1.013  105 Pa1 bar = 105 Pa1 eV = 1.602  10–19 J1 Å = 10–10 mPage 19 of 19 1234567891011121314151617181 H1.00792He4.00263Li6.9414Be9.01225 B10.8116 C12.0117 N14.0078 O15.9999 F18.99810Ne20.18011Na22.99012Mg24.30513Al26.98214Si28.08615P30.97416S32.06517Cl35.45318Ar39.94819K39.09820Ca40.07821Sc44.95622Ti47.86723V50.94224Cr51.99625Mn54.93826Fe55.84527Co58.93328Ni58.69329Cu63.54630Zn65.40931Ga69.72332Ge72.6433As74.92234Se78.9635Br79.90436Kr83.79837Rb85.46838Sr87.6239Y88.90640Zr91.22441Nb92.90642Mo95.9443Tc(98)44Ru101.0745Rh102.9146Pd106.4247Ag107.8748Cd112.4149In114.8250Sn118.7151Sb121.7652Te127.6053I126.9054Xe131.2955Cs132.9156Ba137.3357-7172Hf178.4973Ta180.9574W183.8475Re186.2176Os190.2377Ir192.2278Pt195.0879Au196.9780Hg200.5981Tl204.3882Pb207.283Bi208.9884Po(209)85At(210)86Rn(222)87Fr(223)88Ra(226)89-103104Rf(261)105Db(262)106Sg(266)107Bh(264)108Hs(277)109Mt(268)110Ds(271)111Rg(272)112Cn(285)113Nh(286)114Fl(289)115Mc(290)116Lv(293)117Ts(294)118Og(294)57La138.9158Ce140.1259Pr140.9160Nd144.2461Pm(145)62Sm150.3663Eu151.9664Gd157.2565Tb158.9366Dy162.5067Ho164.9368Er167.2669Tm168.9370Yb173.0471Lu174.9789Ac(227)90Th232.0491Pa231.0492U238.0393Np(237)94Pu(244)95Am(243)96Cm(247)97Bk(247)98Cf(251)99Es(252)100Fm(257)101Md(258)102No(259)103Lr(262)