Problems CHEMISTRY FOR A BETTER TOMORROW July 25, 2020 52nd International Chemistry Olympiad, Istanbul, TURKEY Instructions Only write with pen. Your calculator should be non-programmable. This examination has 9 problems. You will have 5 hours to solve the exam. Begin only when the START command is given. All results must be written in the appropriate boxes in pen in the designated areas on the answer sheets. Use the back of the exam sheets if you need scratch paper. Remember that answers written outside the answer boxes will not be graded. Write relevant calculations in the appropriate boxes when necessary. Full marks will be given for correct answers only when your work is shown. The invigilator will announce a 30-minute warning before the Stop command. You must stop working when the STOP command is given. Failure to stop writing will lead to the nullification of your exam. The official English version of this examination is available on request only for clarification. You are not allowed to leave your working place without permission. If you need any assistance (broken calculator, need to visit a restroom, etc), raise hand and wait until an invigilator arrives. GOOD LUCK! 1 52nd International Chemistry Olympiad, Istanbul, TURKEY Problems & Grading Information Problem Title Total % of Score Total Score 1 Two Beauties of Turkey: the Van Cat and 24 8 the Ankara Cat 2 A Tale of a Reactive Intermediate 77 10 3 (±)-Coerulescine 51 8 4 Symmetry Does Matter! 66 10 5 Konya, Carrot, Beta-Carotene, Vitamin-A, 100 14 Immune System, Vision 6 Thermodynamics through an Interstellar 80 12 Journey 7 Phthalocyanines 85 12 8 Boron Compounds and Hydrogen Storage 58 14 9 Quantification of Heavy Metal Ions 100 12 TOTAL 641 100 2 52nd International Chemistry Olympiad, Istanbul, TURKEY Table of Contents Authors ....................................................................................................................................... 4 Physical Constants and Equations .............................................................................................. 5 Periodic Table of Elements ........................................................................................................ 6 1H-NMR Chemical Shifts ........................................................................................................... 7 Typical Coupling Constants ....................................................................................................... 7 13C-NMR Chemical Shifts .......................................................................................................... 8 IR Absorption Frequency Table ................................................................................................. 8 Problem 1. Two Beauties of Turkey: the Van Cat and the Ankara Cat ................................... 10 Problem 2. A Tale of a Reactive Intermediate ......................................................................... 13 Problem 3. (±)-Coerulescine..................................................................................................... 17 Problem 4. Symmetry Does Matter! ......................................................................................... 20 Problem 5. Konya, Carrot, Beta-Carotene, Vitamin-A, Immune System, Vision.................... 24 Problem 6. Thermodynamics through an Interstellar Journey ................................................. 28 Problem 7. Phthalocyanines ..................................................................................................... 32 Problem 8. Boron Compounds and Hydrogen Storage ........................................................... 36 Problem 9. Quantification of Heavy Metal Ions ...................................................................... 40 3 52nd International Chemistry Olympiad, Istanbul, TURKEY Authors ALANYALIOĞLU, Murat, Atatürk University AYDOĞAN, Abdullah, İstanbul Technical University BURAT, Ayfer Kalkan, İstanbul Technical University DAĞ, Ömer, Bilkent University DAŞTAN, Arif, Atatürk University KILIÇ, Hamdullah, Atatürk University METİN, Önder, Koç University ÖZTÜRK, Turan, İstanbul Technical University SARAÇOĞLU, Nurullah, Atatürk University TÜRKMEN, Yunus Emre, Bilkent University ÜNLÜ, Caner, İstanbul Technical University YILMAZ, İsmail, İstanbul Technical University YURTSEVER, Mine, İstanbul Technical University Editor: SARAÇOĞLU, Nurullah, Atatürk University 4 52nd International Chemistry Olympiad, Istanbul, TURKEY Physical Constants and Equations 23 −1 Avogadro's number, 푁퐴 = 6.0221 × 10 푚표푙 −23 −1 Boltzmann constant, 푘퐵 = 1.3807 × 10 퐽퐾 Universal gas constant, 푅 = 8.3145 퐽퐾−1푚표푙−1 = 0.08205 푎푡푚 퐿 퐾−1푚표푙−1 Speed of light, 푐 = 2.9979 × 108푚푠−1 Planck's constant, ℎ = 6.6261 × 10−34 퐽 푠 Faraday’s constant, 퐹 = 9.6485 × 104 퐶 푚표푙−1 −31 Mass of electron, 푚푒 = 9.1093 × 10 푘 Standard pressure, 푃 = 1 푏푎푟 = 105 푃푎 5 Atmospheric pressure, 푃푎푡푚 = 1.01325 × 10 푃푎 = 760 푚푚퐻 = 760 푡표푟푟 Zero of the Celsius scale, 273.15 퐾 1 picometer (pm) = 10−12 푚; 1Å = 10−10 푚; 1 nanometer (nm) = 10−9 푚 1 푒푉 = 1.6 × 10−19 퐽 1 푐푎푙 = 4.184 퐽 1 푎푚푢 = 1.6605 × 10−27 푘 Charge of an electron: 1.6 × 10−19 퐶 Ideal gas equation: 푃푉 = 푛푅푇 Enthalpy: 퐻 = 푈 + 푃푉 Gibbs free energy: 퐺 = 퐻 − 푇푆 훥퐺 = ∆퐺0 + 푅푇푙푛푄 ퟎ 0 ∆풓푮 = −푅푇푙푛퐾 = −푛퐹퐸푐푒푙푙 Entropy change: 푞푟푒푣 ∆푆 = , where qrev is heat for the reversible process 푇 푉 ∆푆 = 푛푅푙푛 2 (for isothermal expansion of an ideal gas) 푉1 푅푇 퐶 Nernst equation: 퐸 = 퐸0 + 푙푛 표푥푖푑푎푡푖표푛 푛퐹 퐶푟푒푑푢푐푡푖표푛 ℎ푐 Energy of a photon: 퐸 = 휆 Integrated rate law Zeroth-order: [퐴] = [퐴]0 − 푘푡 First-order: 푙푛[퐴] = 푙푛[퐴]0 − 푘푡 1 1 Second order: = + 푘푡 [퐴] [퐴]0 Arrhenius equation: 푘 = 퐴푒−퐸푎/푅푇 Equation of linear calibration curve: 푦 = 푚푥 + 푛 Lambert–Beer equation: 퐴 = 휀푙푐 5 52nd International Chemistry Olympiad, Istanbul, TURKEY Periodic Table of Elements 1 18 1 atomic number 2 H 2 Symbol 13 14 15 16 17 He 1.008 atomic weight 4.003 3 4 5 6 7 8 9 10 Li Be B C N O F Ne 6.94 9.01 10.81 12.01 14.01 16.00 19.00 20.18 11 12 13 14 15 16 17 18 Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S Cl Ar 22.99 24.31 26.98 28.09 30.97 32.06 35.45 39.95 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 39.10 40.08 44.96 47.87 50.94 52.00 54.94 55.85 58.93 58.69 63.55 65.38 69.72 72.63 74.92 78.97 79.90 83.80 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 85.47 87.62 88.91 91.22 92.91 95.95 - 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3 55 56 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Cs Ba 57-71 Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 132.9 137.3 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 - - - 87 88 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 Fr Ra 89-103 Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og - - - - - - - - - - - - - - - - - 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 138.9 140.1 140.9 144.2 - 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.0 175.0 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr - 232.0 231.0 238.0 - - - - - - - - - - - Copyright © 2018 International Union of Pure and Applied Chemistry Reproduced by permission of the International Union of Pure and Applied Chemistry 6 52nd International Chemistry Olympiad, Istanbul, TURKEY 1H-NMR Chemical Shifts Typical Coupling Constants 7 52nd International Chemistry Olympiad, Istanbul, TURKEY 13C-NMR Chemical Shifts IR Absorption Frequency Table Functional Absorption Frequency Type of Vibration Intensity Group Region (cm–1) Alcohol (stretch, H-bonded) 3600–3200 strong, broad O–H (stretch, free) 3700–3500 strong, sharp C–O (stretch) 1150–1050 strong Alkane stretch 3000–2850 strong C–H bending 1480–1350 variable Alkene stretch 3100–3010 medium =C–H bending 1000–675 strong C=C stretch 1680–1620 variable Alkyl Halide C–F stretch 1400–1000 strong C–Cl stretch 800–600 strong C–Br stretch 600–500 strong C–I stretch 500 strong Alkyne C–H stretch 3300 strong, sharp variable, not present in CC stretch 2260–2100 symmetrical alkynes Amine medium (primary amines have two bands; secondary amines N–H stretch 3500–3300 have one band, often very weak) 8 52nd International Chemistry Olympiad, Istanbul, TURKEY C–N stretch 1360–1080 medium-weak N–H bending 1600 medium Aromatic C–H stretch 3100–3000 medium C=C stretch 1600–1400 medium-weak, multiple bands Carbonyl C=O stretch 1820–1670 strong Acid C=O stretch 1725–1700 strong O–H stretch 3300–2500 strong, very broad C–O stretch 1320–1210 strong Aldehyde C=O stretch 1740–1720 strong C–H stretch 2850–2820 & 2750–2720 medium, two peaks Amide C=O stretch 1690–1640 strong stretch 3500–3100 unsubstituted have two bands N–H bending 1640–1550 Anhydride C=O stretch 1830–1800 &1775–1740 two bands Ester C=O stretch 1750–1735 strong C–O stretch 1300–1000 two bands or more Ketone acyclic stretch 1725–1705 strong stretch 3-membered - 1850 strong stretch 4-membered - 1780 strong cyclic stretch 5-membered - 1745 strong stretch 6-membered - 1715 strong stretch 7-membered - 1705 strong ,- stretch 1685–1665 strong unsaturated conjugation moves absorptions to lower wavenumbers aryl ketone stretch 1700–1680 strong Ether C–O stretch 1300–1000 (1150–1070) strong Nitrile CN stretch 2260–2210 medium Nitro 1560–1515 & N–O stretch strong, two bands 1385–1345 9 52nd International Chemistry Olympiad, Istanbul, TURKEY Problems Problem 1 Question 1.1 1.2 1.3 Total 8% of the total Points 14 4 6 24 Problem 1. Two Beauties of Turkey: the Van Cat and the Ankara Cat The most beautiful of cats, the Van cat is a pure breed living only in Lake Van basin.