Dusanka Filipovic. Chapter 2 Reactions of Organic Compounds MHR 69

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1 anadians in hemistry Dusanka Filipovic When Dusanka Filipovic was a teenager, she liked hiking, playing volleyball, and working as a camp counsellor. Now she is a successful chemical engineer who develops and markets technology that helps the environment. What do her early pursuits have to do with her engineering career? Both require creativity, persistence, and an ability to work under pressure, says Filipovic. Filipovic was born and grew up in Belgrade, in the former Yugoslavia. She attended the University of Belgrade, and graduated with a degree in chemical engineering. Attracted by anada s technical advances, she came here after winning a scholarship to study at McMaster University in amilton, ntario. anada has become her home. Filipovic has worked hard to break down barriers for women in the fields of engineering and business. In 1974, she became the first female professional engineer employed by a major chemical producing company. The National Museum of Science and Technology in ttawa, ntario, has featured her work as part of an exhibit on women inventors. Since the 1980s, Filipovic has concentrated on developing environmentally friendly technologies. She is the co-inventor of a patented process known as Blue Bottle technology. This process is used to recover and recycle halogenated hydrocarbons, such as chlorofluorocarbons (Fs) and other ozone-depleting substances (DS), from damaged or unused residential refrigerators and automotive air conditioners. Using adsorption, the binding of molecules or particles to a surface, Blue Bottle TM technology acts as a selective molecular sieve to capture refrigerant gases so that they can be safely stored and re-used. A non-pressurized Blue Bottle TM cylinder, packed with an adsorbent, synthetic zeolite called alozite TM, is connected to the back of a refrigeration or air-conditioning unit. Zeolites are porous aluminosilicate minerals that commonly contain sodium and calcium as major cations (positively charged ions) and are capable of ion exchange. (Zeolites contain water molecules that allow reversible dehydration, and they are often used as water softeners.) The alozite TM adsorbs the refrigerants that are released from the unit at ambient temperatures, under atmospheric pressure. nce the adsorbent is saturated, the Blue Bottle TM cylinder is sent to a central reclamation facility, where the refrigerants are reclaimed and stored. The Blue Bottle TM cylinders can be re-used after the refrigerants have been collected. eclaimed halogenated hydrocarbons can be used as refrigerants, solvents, cleaners, fumigants, and fire retardants. In 1991, Filipovic formed her own company to commercialize Blue Bottle TM technology. In 1999, she founded a new company, which uses a process similar to Blue Bottle TM technology to capture and convert greenhouse gas emissions from hospital operating rooms. These emissions had previously been discharged into the atmosphere. Filipovic has this advice for aspiring engineers and scientists: nce you recognize what it is you want to pursue, make sure you take advantage of every training opportunity offered to you. I became an engineer because I wanted to be able to create something new, and monitor and enjoy the results of my work... I am working to make a significant contribution that will live on after me. hapter 2 eactions of rganic ompounds M 69

2 Electronic Learning Partner Go to the hemistry 12 Electronic Learning Partner for more information about aspects of material covered in this section of the chapter. eactions of Aromatic ompounds As you learned in hapter 1, aromatic compounds do not react in the same way that compounds with double or triple bonds do. Benzene s stable ring does not usually accept the addition of other atoms. Instead, aromatic compounds undergo substitution reactions. A hydrogen atom or a functional group that is attached to the benzene ring may be replaced by a different functional group. Figure 2.6 shows two possible reactions for benzene. Notice that iron(iii) bromide, Fe 3, is used as a catalyst in the substitution reaction. An addition reaction does not occur because the product of this reaction would be less stable than benzene. benzene Fe bromine hydrobromic acid and bromobenzene (actual product) 5,6-dibromo-1,3-cyclohexadiene (does not form) Figure 2.6 The bromine does not add to benzene in an addition reaction. Instead, one of the atoms on the benzene ring is replaced with a atom in a substitution reaction. eactions of Alcohols Alcohols can react in several ways, depending on the reactants and on the conditions of the reaction. For example, alcohols can undergo substitution with halogen acids, elimination to form alkenes, and oxidation to form aldehydes, ketones, or carboxylic acids. Substitution eactions of Alcohols When a halogen acid, such as l,, or I, reacts with an alcohol, the halogen atom is substituted for the group of the alcohol. This is shown in Figure 2.7(A). The reverse reaction takes place when an alkyl halide reacts with in a basic solution. See Figure 2.7(B). A l 3 2 l + 2 B 3 2 l l Figure 2.7 (A) Ethanol reacts with hydrochloric acid to produce chloroethane. (B) In a basic solution, the reverse reaction takes place. A hydroxide ion reacts with chloroethane to produce ethanol. Elimination eactions of Alcohols When an alcohol is heated in the presence of the strong acid and dehydrating agent, 2 S 4, an elimination reaction takes place. This type of reaction is shown in Figure 2.8, on the next page. The group and one atom leave the molecule, and water is produced. As a result, the molecule forms a double bond. Because water is produced, this type of reaction is also called a dehydration (meaning loss of water ) reaction. 70 M Unit 1 rganic hemistry

3 2 S ethanol ethene water Figure 2.8 The symbol is used in chemistry to represent heat added to a reaction. xidation of Alcohols In the presence of an oxidizing agent, an alcohol is oxidized to form an aldehyde or a ketone. A primary alcohol is oxidized to an aldehyde. If the aldehyde is oxidized further, it becomes a carboxylic acid. primary alcohol + [] + [] aldehyde carboxylic acid A secondary alcohol is oxidized to a ketone. All the carbon bonding sites are now occupied with bonds to carbon and oxygen, so no further oxidation is possible. + [] + [] secondary alcohol ketone no reaction A tertiary alcohol cannot be oxidized. arbon can form up to four bonds, but all possible bonding sites are already occupied. bonds can be broken by an oxidizing agent. n the carbon atom of a tertiary alcohol, however, there is no hydrogen atom available to be removed. bonds are too strong to be broken by an oxidizing agent. + [] no reaction tertiary alcohol The following Sample Problem shows how to predict the products of reactions of alcohols. hapter 2 eactions of rganic ompounds M 71

4 Sample Problem Predicting the eaction of an Alcohol Problem Name each type of reaction. Then predict and name the products. (a) [] (b) S 4 (c) Solution (a) The reactant is a secondary alcohol, and an oxidizing agent is present. Therefore, this must be oxidation. You know that a secondary alcohol is oxidized to a ketone. The ketone must have the same carbon-carbon bonds, and the same number of carbon atoms, as the reacting alcohol. Therefore, the ketone must be 2-butanone [] butanol oxidizing agent 2-butanone PBLEM TIP In many elimination reactions, water is produced. The formation of water is a strong driving force for many reactions. (b) This reaction takes place in the presence of heat and sulfuric acid, 2 S 4. It is an elimination reaction. The product is an alkene, with the same number of carbon atoms as the reacting alcohol. Since this reaction is an elimination reaction, a small molecule (in this case, water) must be eliminated as the second product. The organic product is propene S propanol propene water (c) In this reaction, an alcohol reacts with hydrobromic acid,. This is a substitution reaction. The product is an alkyl halide, with the same carbon-carbon bonds, and the same number of carbon atoms, as the reacting alcohol. The alkyl halide is 2-bromopropane. The second product is water propanol hydrobromic acid 2-bromopropane water 72 M Unit 1 rganic hemistry

5 Practice Problems 9. Name each type of reaction. (a) 1-propanol + l 1-chloropropane + 2 (b) 1-butanol + [] butanal (c) l + Na Nal (d) Draw the structures of the reactants and products in parts (a) and (b) of question Name each type of reaction. 2 S (a) (b) S [] (i) + [] (ii) (c) (d) Na (e) [] (f) + l 12. Draw and name the products of each reaction in question Is the following reaction possible? Why or why not? [] 3 In the following investigation, you will carry out the oxidation of different alcohols. hapter 2 eactions of rganic ompounds M 73