PREPARATORY PROBLEMS 52nd International Chemistry Olympiad Istanbul, Turkey Preparatory Problems CHEMISTRY FOR A BETTER TOMORROW First edition (31.01.2020) 52nd International Chemistry Olympiad, Istanbul, TURKEY Preface We are very glad to provide Preparatory Problems for the 52nd International Chemistry Olympiad, which will be held in 2020 in Istanbul, Turkey. We prepared these problems with the intention of facilitating the training and preparation of participants. The contents of the problems have been carefully selected so as to cover a broad range of challenging topics that can be encountered in modern as well as classical chemistry. The problems can be solved by applying the fundamental principles of chemistry covered at high school level along with 6 topics of advanced difficulty for the theoretical section, and 3 topics of advanced difficulty for the practical section. These advanced topics are listed explicitly under “Topics of Advanced Difficulty” and their applications are demonstrated in the tasks. We expect the participants to be familiar with these advanced topics. The problems listed in this booklet consist of 25 theoretical and 8 practical tasks. The solutions will be sent to the Head Mentor of each country by e-mail by March 1st, 2020 and will be published by May 15th, 2020 on our IChO 2020 website. We welcome any comments, suggestions, corrections, or questions about the problems at [email protected]. The International Chemistry Olympiad presents a great opportunity to inspire younger generations to pursue a career in fundamental sciences and make a positive influence on public attitudes towards science, and in particular chemistry. We hope you will enjoy solving these problems and we look forward to seeing you in July in Istanbul, Turkey. Acknowledgments I would like to express my deep gratitude to all the authors for their dedication and effort in contributing to the Preparatory Problems as well as the members of the International Steering Committee for their valuable comments and suggestions. We are also highly appreciative of the Scientific and Technological Research Council of Turkey (TUBITAK), in collaboration with the Faculty of Science, Istanbul Technical University (ITU), for facilitating all organizational tasks before and during IChO 2020. On behalf of the Scientific Committee, Dr. Arif DAŞTAN 1 52nd International Chemistry Olympiad, Istanbul, TURKEY Table of Contents Authors ....................................................................................................................................... 4 Physical Constants and Equations .............................................................................................. 5 Periodic Table of Elements ........................................................................................................ 7 1H NMR Chemical Shifts ........................................................................................................... 8 Typical Coupling Constants ....................................................................................................... 8 13C NMR Chemical Shifts .......................................................................................................... 9 IR Absorption Frequency Table ................................................................................................. 9 Fields of Advanced Difficulty .................................................................................................. 11 Part I: Theoretical Problems ..................................................................................................... 13 Problem 1. Salvia Species Growing in Turkey: Isolation and Total Synthesis of Abietane Diterpenoids ............................................................................................................................. 14 Problem 2. Istanbulins and Related Sesquiterpene Natural Products ....................................... 19 Problem 3. Çay, Cha, Chai, Te, Tea, Tee, Thé, Thee, and Earl Grey Tea Flavor: Bergamot .. 23 Problem 4. Early Russian Organic Chemists and Markovnikov’s Rule .................................. 25 Problem 5. Arndt–Eistert Homologation .................................................................................. 29 Problem 6. Atovaquone ............................................................................................................ 32 Problem 7. Which is (±)-Trikentrin A? .................................................................................... 36 Problem 8. Stereoisomers of 1,2,3-Triphenylpropane-1,3-diol ................................................ 40 Problem 9. NMR, Symmetry, and Structural Analysis ............................................................ 41 Problem 10. Woodward–Hoffmann Rules and Pericyclic Reactions ....................................... 44 Problem 11. Benzoporphyrin .................................................................................................... 48 Problem 12. Blue to Green, Turquoise ..................................................................................... 52 Problem 13. Spinel Oxides ....................................................................................................... 58 Problem 14. Platinum Complexes as Anticancer Drugs........................................................... 61 Problem 15. Sodium Compounds from Salt ............................................................................. 65 Problem 16. Thermal Springs of Turkey and Sulfur Chemistry .............................................. 68 Problem 17. Electrochemical Determination of Rutin ............................................................. 72 Problem 18. Particle in a Box Problem: Free Electron Model ................................................. 76 Problem 19. Harmonic Oscillator and Rigid Rotor Models ..................................................... 78 Problem 20. Journey to Different Earth-Like Planets .............................................................. 80 Problem 21. Rate Constant Models and Kinetic Isotope Effect ............................................... 82 Problem 22. Parallel Reaction Kinetics .................................................................................... 85 Problem 23. Reaction Kinetics with Absorbance Measurement .............................................. 87 2 52nd International Chemistry Olympiad, Istanbul, TURKEY Problem 24. Acridine Orange / DNA Binding Interactions ..................................................... 89 Problem 25. Spectrophotometric Determination of an Antihistaminic Drug ........................... 93 Part II: Practical Problems ........................................................................................................ 95 Problem P1. Drug Delivery from a Polymeric Hydrogel System ............................................ 99 Problem P2. Determination of the Total Carbon Content of Oltu Stone (Black Amber) Samples ................................................................................................................................... 104 Problem P3. Spectrophotometric Determination of the Equilibrium Constant for the Formation of a Complex .......................................................................................................................... 108 Problem P4. 1-Bromobutane .................................................................................................. 112 Problem P5. Cannizzaro Reaction .......................................................................................... 116 Problem P6. 2,3-Dihydro-5,6-diphenylpyrazine .................................................................... 123 Problem P7. Determination of Rate Constants for n-Butyl Acetate Hydrolysis .................... 126 Problem P8. Activation Energy of Bromide / Bromate Reaction .......................................... 129 3 52nd International Chemistry Olympiad, Istanbul, TURKEY Authors ALANYALIOĞLU, Murat, Atatürk University ARSLAN, Yasin, Burdur Mehmet Akif Ersoy University AYDOĞAN, Abdullah, İstanbul Technical University BOZKAYA, Uğur, Hacettepe University BURAT, Ayfer Kalkan, İstanbul Technical University DAĞ, Ömer, Bilkent University DAŞTAN, Arif, Atatürk University (Chair of Scientific Committee) ELTUĞRAL, Nurettin, Karabük University GÖLCÜ, Ayşegül, İstanbul Technical University KANBUR, Yasin, Karabük University KILIÇ, Hamdullah, Atatürk University METİN, Önder, Koç University SARAÇOĞLU, Nurullah, Atatürk University TÜRKMEN, Yunus Emre, Bilkent University ÜNLÜ, Caner, İstanbul Technical University YILMAZ, İsmail, İstanbul Technical University Edited by: SARAÇOĞLU, Nurullah, Atatürk University 4 52nd International Chemistry Olympiad, Istanbul, TURKEY Physical Constants and Equations 23 −1 Avogadro's constant, 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 constant, 퐹 = 9.6485 × 104 퐶 푚표푙−1 −31 Mass of electron, 푚푒 = 9.10938215 × 10 푘푔 Standard pressure, 푃 = 1 푏푎푟 = 105 푃푎 5 Atmospheric pressure, 푃푎푡푚 = 1.01325 × 10 푃푎 = 760 푚푚퐻푔 = 760 푡표푟푟 Zero of the Celsius scale, 273.15 퐾 1 picometer (pm) = 10−12 푚; 1퐴0 = 10−10 푚; 1 nanometer (nm) = 10−9 푚 1 푒푉 = 1.6 × 10−19 퐽 1 푐푎푙 = 4.184 퐽 1 푎푚푢 = 1.66053904 × 10−27 푘푔 Charge of an electron: 1.6 × 10−19 퐶 Ideal gas equation: 푃푉 = 푛푅푇 Enthalpy: 퐻 = 푈 + 푃푉 Gibbs free energy: 퐺 = 퐻 − 푇푆