IChO 2009, Експеримент — Задача 1. Practical problem1 — An Environmentally Friendly Aldol Condensation
41st International Chemistry Olympiad — Cambridge2009 — Practical problems (Volume3 collection edition2014)
Внимание: Бележка към темата
Source edition: The Competition Problems from the International Chemistry Olympiads, Volume 3, edited by Anton Sirota, IUVENTA / IChO International Information Centre, Bratislava, 2014. The collection normalizes task numbering and omits some original grading points, practical instructions and data-dependent key material. Every item actually printed in this Cambridge 2009 section is retained. The referenced practical answer booklet, TLC template and Practical 1 carbon NMR spectrum were not obtained. Reproduced for teaching purposes with the printed Volume 3 attribution and rights notice; commercial publication/distribution requires permission from the copyright holder.
Collection edition and native section
The Competition Problems from the International Chemistry Olympiads, Volume3,41st–45th IChO2009–2013. Edited by Anton Sirota. IUVENTA–Slovak Youth Institute, Bratislava2014. This scoped paper preserves only the41st International Chemistry Olympiad,18–27July2009, Cambridge, United Kingdom.

Native rights statement and archive qualification
You are free to copy, distribute, transmit or adapt this publication or its parts for unlimited teaching purposes, you are obliged, however, to attribute your copies, transmissions or adaptations with a reference to "The Competition Problems from the International Chemistry Olympiads, Volume 3" as it is commonly required in the chemical literature. The problems copied cannot be published and distributed for commercial proposes. The above conditions can only be waived if you get permission from the copyright holder.
Copyright2014IUVENTA–IChO International Information Centre; ISBN978-80-8072-154-1. Attribution: The Competition Problems from the International Chemistry Olympiads, Volume3, edited by Anton Sirota, Bratislava2014.
Source note: This wording permits copying, distribution, transmission and adaptation for unlimited teaching purposes with the required Volume3 reference. It forbids commercial publication/distribution unless the copyright holder waives the conditions. This free educational archive retains the required Volume 3 attribution and this rights notice. Reproduction is presented for teaching purposes under the printed grant; no commercially unrestricted permission is claimed. The publisher must assess this obtained statement before adoption.

Issued by IUVENTA – Slovak Youth Institute in 2014 with the financial support of the Ministry of Education of the Slovak Republic. Number of copies: 250. Not for sale.
International Chemistry Olympiad, International Information Centre, IUVENTA – Slovak Youth Institute, Búdková 2, SK 811 04 Bratislava 1, Slovakia. E-mail: anton.sirota@stuba.sk. Web: www.icho.sk.
Full native editorial preface
Preface This publication contains 39 theoretical and 14 practical competition problems from the 41st – 45th International Chemistry Olympiads (IChO) organized in the years 2009 – 2013. It has been published by the IChO International Information Centre in Bratislava (Slovakia) as a continuation of the preceding Volumes 1 and 2 published on the occasion of the 40th anniversary of the IChO with the titles: • The competition problems from the International Chemistry Olympiads, Volume 1, 1st – 20th IChO, 1968 – 1988 (IUVENTA, Bratislava, 2008). • The competition problems from the International Chemistry Olympiads, Volume 2, 21st – 40th IChO, 1989 – 2008 (IUVENTA, Bratislava, 2009). Not less than 318 theoretical and 110 practical problems were set in the IChO during the forty-five years of its existence. In the elaboration of this collection the editor had to face certain difficulties because the aim was not only to make use of past recordings but also to give them such a form that they may be used in practice and further chemical education. Consequently, it was necessary to make some corrections in order to unify the form of the problems (numbering the tasks of the particular problems, solution inserted immediately after the text of the problem, solutions without grading points and special graphs used for grading of practical problems). Nevertheless, the mentioned corrections and changes do not concern the contents and language of the competition problems. The practical problems set in the IChO competitions, contain as a rule some instructions, list of apparatuses available, chemicals on each desk and those available in the laboratory, and the risk and safety phrases with regard to the chemicals used. All of these items are important for the competitors during the competition but less important for those who are going to read the competition tasks of this collection and thus, they are omitted. Some parts of the solutions of practical problems are also left out since they require the experimental data which could be obtained by experiments during the practical part of the IChO competition. In this publication SI quantities and units are preferred. Only some exceptions have been made when, in an effort to preserve the original text, the quantities and units have been used that are not SI. Although the numbers of significant figures in the results of some solutions do not obey the criteria generally accepted, they were left without change.
Unfortunately, the authors of the particular competition problems are not known and due to the procedure of creation of the IChO competition problems, it is impossible to assign any author's name to a particular problem. Nevertheless, responsibility for the scientific content and language of the problems lies exclusively with the organizers of the particular International Chemistry Olympiads. This review of the competition problems from the 41st – 45th IChO should serve to both competitors and their teachers as a source of further ideas in their preparation for this difficult competition. For those who have taken part in some of these International Chemistry Olympiads the collection of the problems could be of help as archival and documentary material. In the previous forty-five years many known and unknown people - teachers, authors, pupils, and organizers proved their abilities and knowledge and contributed to the success of this already well known and world-wide competition. We wish to all who will organize and attend the future International Chemistry Olympiads, success and happiness. Bratislava, July 2014 Anton Sirota, editor
Source note: The preface describes general editorial omissions. This Cambridge section nevertheless prints practical chemical lists, procedures and selected grading graphs, all retained. Missing original answer-booklet/NMR material is not invented.
Условие
In attempts to become more environmentally friendly,increasing attention is being paid to minimising the large amounts of solvents used in chemical reactions. In the following experiment,an aldol condensation reaction is carried out in the absence of solvent.

Chemicals
- 3,4-dimethoxybenzaldehyde, 0.50 g pre-weighed in vial,
- 1-indanone, 0.40 g pre-weighed in vial,
- NaOH, 0.10 g pre-weighed in vial,
- HCl, aqueous solution, c = 3.0 mol dm⁻³, 10 cm³ in a bottle,
- Diethyl ether : Heptane (1:1), 25 cm³ in a bottle,
- Ethyl ethanoate, 1 cm³ in a small vial,
- Sample of 1-indanone dissolved in ethyl ethanoate, 1.0 cm³ in small vial,
- Sample of 3,4-dimethoxybenzaldehyde dissolved in ethyl ethanoate, 1.0 cm³ in small vial,
- Ethyl alcohol (9:1 mixture with H₂O): 100 cm³ in a bottle.
Procedure
(a) Add 3,4-dimethoxybenzaldehyde (DMBA 0.50 g, 3.0 mmol) and 1-indanone (0.40 g, 3.0 mmol) to a 25 cm³ beaker. Use a metal spatula to scrape and crush the two solids together until they become a clear oil.
(b) Add NaOH (0.1 g, 2.5 mmol) to the reaction mixture, crush any lumps formed and continue scraping and crushing until the mixture becomes solid.
(c) Allow the mixture to stand for 20 minutes. Then add 4 cm³ of aqueous HCl solution (c = 3 mol dm⁻³) and scrape around the beaker so as to dislodge all product from the walls. Use a flat-ended glass rod to crush any lumps present.
1.1 Measure and record the pH of the solution.
(d) Isolate the crude product using vacuum filtration through a Hirsch funnel. Rinse out the beaker with 2 cm³ of aqueous HCl solution (c = 3 mol dm⁻³) and pour over the crude product in Hirsch funnel to wash, continuing to pull air through the solid for 10 minutes to facilitate drying.
1.2 Report the mass of the crude product (which may still be a little wet), using the vial labelled ‘CPA’ as a container.
(e) Take a TLC to assess whether the reaction is complete, using Et₂O : heptane (1 : 1) as the eluant. Solutions of both starting materials in ethyl ethanoate are provided. The crude product is soluble in ethyl ethanoate. [Note: Three TLC plates are provided. You may use them all, but you must only submit one in your labelled Ziploc bag. This should be the plate that you draw in your answer booklet.]
1.3 Using UV light to visualize, draw around the spots on the plate in pencil to show where they are, copy your plate onto the answer sheet, and place your plate in the Ziploc bag labelled with your student code. Determine and record the relevant RF values.
(f) Using a 100 cm³ conical flask with a stir bar in the bottom, recrystallize the product from a mixture of EtOH : H₂O (9 : 1). (N.B. A hot filtration, using the glass funnel provided, is required as part of this process to remove small amounts of insoluble impurities.) Any lumps may be crushed using the flat-ended glass rod. Allow the conical flask containing the filtered solution to cool to room temperature and then cool in an ice bath (use the polystyrene tray to make the ice bath in) for one hour before filtration through a Büchner funnel to collect your product. Suck air through for 10 minutes to dry the product. Place your product in the vial marked with your code and labelled ‘RPA’.
1.4 Report the mass of the purified product.
Product A could have one of the two formulae: C₁₈H₁₈O₄ or C₁₈H₁₆O₃.
1.5 Draw the structure of every geometrical and/or stereoisomer with formula:
i) C₁₈H₁₈O₄,
ii) C₁₈H₁₆O₃
that could be formed in this reaction. Indicate how many peaks you would expect in total in the¹³C NMR spectrum of each.
1.6 The¹³C NMR spectrum for A is shown in the practical instructions. Peaks due to the solvent,CDCl₃,are marked with an asterisk. With the aid of the spectrum,decide which is the correct formula for A. Mark on the answer sheet one of the two boxes below to indicate which you have chosen:
C₁₈H₁₈O₄:□
C₁₈H₁₆O₃:□
1.7 Report the mass and calculate the percentage yield of the purified product, based on the formula you gave for its structure.
Решение
1.1 Values of pH=1–2are accepted.
1.2 Because the sample is not completely dry,often this mass is above100%of that expected. Usual range is800–1000mg(94–117%). Zero points for any less than400mg(product has been lost).
1.3 Evaluation
Maximum points if both standards plus crude product are present and no starting materials remain and student has co-spotted crude product with one or both starting materials and solvent front is marked and plate is not over-or under-loaded.
Minus points if:
- plate has no co-spots,
- substantial amount of either or both starting materials remain,
- over-or under-loading occurs which does not interfere with evaluation,
- over-or under-loading occurs and does interfere with evaluation,
- over-or under-loading occurs and prevents evaluation,
- any sample is missing.
The relevant RF values:
| Chemical | RF |
|---|---|
| 3,4-DMBA | 0.16–0.25 |
| 1-Indanone | 0.34–0.43 |
| CPA | 0.11–0.20 |
Maximum points if both starting materials and reaction product are present with Rf values which fall within those given.
Minus points if:
- RF values are missing for one or more chemicals,
- both starting materials and reaction product are present with RF values which fall outside those given due to the plate running too long or the student having marked the solvent front incorrectly,
- both starting materials and reaction product are present with RF values which fall outside those given,due to an inability to calculate RF values.
1.4(as printed in the key) For C₁₈H₁₈O₄ and C₁₈H₁₆O₃:


1.5(as printed in the key) C₁₈H₁₆O₃.
1.6(as printed in the key) Mass:0.5g(example mass of product).
Calculation:
For formula C₁₈H₁₈O₄:Molar mass=298.324g mol⁻¹. Expect:0.3mmol maximum=0.895g.
.
For formula C₁₈H₁₆O₃:Molar mass=280.308g mol⁻¹. Expect:0.3mmol maximum=0.841g.
.
YIELD
The samples were also weighed by the organizer,before and after drying for one hour in a vacuum desiccator. Sample purity was then checked by¹H and¹³C NMR. The evaluations of the results were adapted to the results obtained by the above measurements.
Source note: Key1.4/1.5/1.6 correspond respectively to question1.5/1.6/1.7; no separate answer for the purified-mass report1.4 is printed. The native0.3mmol maximum is inconsistent with the stated3.0mmol amounts and the printed maximum masses. All printed labels/values are retained. The referenced practical-instruction NMR spectrum and separate answer booklet are absent from this obtained section.
Оригинал в Архива: IChO 41st-45th.pdf · решение от архива: IChO 41st-45th.pdf · допълнителни данни: IChO 41st-45th.pdf