1. «Traces of the Silver Age». Famous Russian poet Sergei Yesenin once wrote: «One who has ever loved can’t love anymore. One who has burnt out can’t be reignited». However, there are examples of substances that are able to burn even if the substances themselves were formed after ignition. Propose several principally different schemes of the kind {starting reagents → burning with formation of «flammable ash» → burning again with formation of the other products}. Show at least three examples with «flammable ash» being in different states of matter.
3. «Uniform for anions». In contrast to organic cations and neutral uncharged molecules, anions of carboxylic acids hardly can permeate the cell membrane. Propose the method of chemical modification of carboxylic anions aimed to increase the membrane permeability of the derivative, and with rapid regeneration of the original anion once inside the cell. Show the mechanism for all of the stages of this process.
5. «Steam distillation». Steam distillation is an extremely convenient purification method for many organic substances. How to certainly predict if the substance would distill with steam, knowing only its chemical formula? Propose other solvents instead of water for the cases where steam distillation is impossible (the substance doesn’t distill with steam, reacts with water etc.) Can the addition of the proposed solvents to the laboratory practice of steam distillation possibly widen the scope of its practical use?
6. «My Precious». Some people are collecting «chemical elements». In such collections one can find «flawless samples» of alkali metals in the sealed ampoules with shiny unoxidized mirror surface. All of alkali metals except lithium. Such a situation occurs also for the alkaline-earth metals: their appearance loses to that of alkali metals. What is the reason of this situation? Propose the method to obtain «flawless» samples of lithium and of alkaline-earth metals.
7. «Self-utilization». Design of the polymeric materials capable of self-destruction under environmental conditions after their disposal is an actual problem. To achieve this purpose, different additives are included to polymeric compositions to accelerate the degradation or to make it possible, if it weren’t. Explain the mechanisms of such acceleration. Compare additives for different types of polymers. Select the best ones for the materials based on polyethylene, polystyrene, rubber and polyamide fiber. Does any additive exist for Teflon? If not, can it exist?
8. «SOS». You, a talented young chemist, are kidnapped and held by unknown people. You are working in a well-equipped chemical lab, but you have no communication with the outside world. All the substances synthesized by you are transferred by villains to other laboratories for analysis, but all the marking is destroyed. Using chemical substances, find a way to transmit a signal about kidnapping and the information that will help your friends to find you.
12. «To make ends meet». This isn’t simple even in everyday life, all the more in chemistry. Synthesis of simplest cyclic compounds, cycloalkanes, is often not a trivial task. Small strained 3- and 4-membered cycles are easy enough to obtain, much more difficult the matter is for big macrocycles. 9- to 14-membered cycles comprise the least synthetically reachable «dead zone». Explain this, at first sight illogical, situation. Propose the synthetic methods which allow for the successful synthesis of these compounds. Why do these exact methods offer a solution to the problem of «dead zone»?
13. «Nettle». Defense from enemies is a vital necessity. One of the defense strategies of organisms is «chemical weapon». Classify the methods of chemical self-defense in the living nature from the purely chemical point of view. Are there any tendencies in the choice of exact defending compounds depending upon natural habitat of the organism and/or its taxonomy (being member of a specific genus, family, class, etc.)?
14. «Antiques dealer». Printed paper degrades with time, becoming yellowish and losing quality. What processes are responsible for this? Can ageing of paper be slowed down or even stopped? Discuss the possibility of existence of the chemical methods that allow the recovery of old paper to its initial state without inflicting damage to printed information. For the paper so damaged that it’s not recoverable anymore, is there a possibility to chemically increase the clarity of the printed info to allow making copies?
15. Experimental task (http://tyc.com.ua/en_US/exp)
«The Dark Side of the Apple». It is well-known that in the air media a fresh cut made on apple turns brown with time. What are the reasons for the change in color? Experimentally research the dependence of the browning rate upon at least five physical and chemical factors. Suggest the hypotheses that explain the observed dependencies. Find out the most effective chemical inhibitor of browning. Propose the effective chemical anti-browner which can be used without loss to the nutritional status and to the taste of the apple.
