Introduction
In July 2012, the 44th International Chemistry Olympiad (IChO) was held in Washington DC. The competition included both practical and written examinations and had 280 students representing 72 countries worldwide. Scientific observers from six additional nations also attended with hopes of joining the event in the near future. The Canadian students were chosen through the combination of a national examination (the Canadian Chemistry Contest, Parts A and C) with a dedicated selection camp that tested both their theoretical knowledge and laboratory skills. Ten students from across the country competed at this camp held at the University of Toronto, June 1 – 7. After a week of gruelling workshops, tests and laboratory sessions, four Ontario students were identified to represent Canada: Run Ze Cao (Martingrove Collegiate Institute); David Pechersky (Vaughan Secondary School); Isabelle Yang (Don Mills Collegiate Institute) and Leslie Ying (University of Toronto Schools). The team members were further trained at the University of Toronto under the guidance of Dr. Stanislaw Skonieczny, based on preparatory problems published by the United States organizers. Dr. Skonieczny and Patrick Kim acted as mentors for the team, while Dr. Tihana Mirkovic and Dr. Russell Boyd (Dalhousie University) joined as scientific observers. More details about the Canadian Chemistry Olympiad (CCO) program can be found in a previous issue of Chem 13 News (November 2011, pages 15-16).
The examinations
This year, the IChO practical examination lasted for five hours and consisted of two fairly straightforward tasks. The first experiment challenged students to plan multiple experiments in advance by requiring them to measure reaction rates and to ultimately determine the order of a reaction as well as the value of the kinetic constant. Students were also required to repeat the experiment with a deuterated reagent and to deduce the likely rate-determining step based on the observed results. All the Canadian students excelled in this task, especially Run Ze Cao, who scored a perfect grade. The second experiment involved preparation of a salen manganese complex and subsequent determination of its formula by titration. This task proved to be more challenging for many participants, and the international jury debated for many hours regarding its set-up and appropriateness. In the end, the Canadian team also fared very well in this experiment, reflecting their thorough preparation in fundamental laboratory techniques.
The physical chemistry theoretical questions covered a range of topics at the 44th IChO. Students were asked to derive a general formula for the quantized energies of linear polycyclic aromatic hydrocarbons (PAHs) based on an analog of a particle in a two-dimensional box. Subsequently, they were required to fill in the energy level diagrams for anthracene and benzene with π electrons and label the energy levels with corresponding quantum numbers. Calculation of the energy gap for three PAHs enabled the students to comment on the relative reactivity of these conjugated molecules and to identify their corresponding absorption spectra. A challenging part of the question was the determination of the Fermi level of graphene. In addition, the unit cell of the superconductor YBCO was analyzed by students through element assignment and the application of Bragg’s law for the determination of unit cell dimensions. They were then required to deduce chemical equations that illustrated the dissolution of YBCO in HCl, and the subsequent treatment of that solution with KI and thiosulfate.
Square-planar platinum complexes were used as model compounds to illustrate stereoisomerism and the trans effect in inorganic chemistry. In an additional part of the question, students were asked to determine rate constants for substitution reactions of square planar complexes. A model study of the functionalization of gold nanoparticles with platinum(IV) complexes for the development of chemotherapy agents was implemented to assess relative masses of the two metals in a given sample. Another inorganic question focused on determining the concentration of thiomolybdate ionic species in a mixture. Here, students had to manipulate data obtained by absorption spectroscopy and implement the systematic treatment of equilibrium. Fundamental knowledge of boron chemistry was tested through structure determination and thermochemistry, which led to the estimation of the dissociation enthalpy of the B-B single bond.
One organic chemistry question considered ways that the molecular structure of DNA may be modified, both naturally and in ways devised by humankind. Students were asked to decide which of the pyrimidine bases (cytosine or thymine) is more nucleophilic towards the alkylation of a single DNA strand. They subsequently had to draw resonance structures of the chosen base and products of its methylation by S-adenosyl methionine.
The next part of this question asked for the identification of intermediates in an asymmetric total synthesis of duocarmycin, a natural product with potent anti-tumour properties. A second task concerned the total synthesis of Varenicline, an oral remedy for smoking addiction. Students were required to draw eight intermediates along a synthetic pathway, with proton NMR data included to aid the identification of stable compounds.
Finally, an example of a Diels-Alder reaction was provided to students. An artificial enzyme was designed to bind the two substrate molecules (diene and dienophile) and catalyze the reaction between them. The task was to draw potential regioisomers, diastereomers and enantiomers that could be formed in the uncatalyzed reaction. Finally, the active site of the enzyme was shown and students were asked to draw the structure of the enzyme-catalyzed reaction product.
Fun time!
Despite the strict and serious impression given from the difficulty of these examination questions, the 44th IChO kept students busy with a very active social program. This year, the students visited several of the world-class museums located in Washington DC as well as many other sites, including the NASA Goddard Space Flight Center, the Library of Congress, the Albert Einstein Memorial, and the Baltimore Aquarium to name but a few. Students also attended a Baltimore Orioles Major League Baseball game at Camden Yards and let out screams at the Kings Dominion amusement park. These social activities presented a great opportunity for the Canadian students to make friends from across the world who share the same passion whilst allowing them to relax during the most stressful week of their lives! The friendships they had formed were quite evident at the closing ceremony where every announced medal was met with joyous applause from all attendees. Their earned medals were as follows: Run Ze Cao: silver medal (placed 60th in the world); Leslie Ying: bronze medal (95th); Isabelle Yang: bronze medal (124th) and David Pechersky: bronze medal (177th). See winners on page 2 of this issue. Medals are awarded to the top 60% of participants.
Contact
For more information about the CCO program, please email Andy Dicks (the National Coordinator) at adicks@chem.utoronto.ca.
