Aim # 43: What are some chemical reactions of hydrocarbons? H.W. # 43 Study p. 650, p. 653, pp. 671-674 Study class notes Ans. ques. p.678 # 22-25; 26a,b; 29 p.680 # 56-58

CH4(g) + O2(g) → CO2(g) + H2O(g) 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g) I Combustion- alkanes are chemically inactive under ordinary conditions. However, they burn readily. CH4(g) + O2(g) → CO2(g) + H2O(g) 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g) In an excess of oxygen, hydrocarbons burn completely to form carbon dioxide and water vapor.

Incomplete combustion will produce carbon monoxide and/or carbon. 2CH4(g) + 3O2(g) → 2CO(g) + 4H2O(g) CH4(g) + O2(g) → C(s) + 2H2O(g) Given that hydrocarbons burn with sufficient oxygen, what would you expect them to be used for?

zymase C6H12O6 → 2C2H5OH + 2CO2 glucose ethanol II Fermentation- in this process, enzymes produced by living organisms act as catalysts. They break down glucose into an alcohol (ethanol) and carbon dioxide. zymase C6H12O6 → 2C2H5OH + 2CO2 glucose ethanol

methane chloromethane III Substitution- the replacement of one kind of atom by another atom or group of atoms in an alkane. Alkanes will react with halogens (F,Cl,Br, I) in sunlight or UV light. H H H–C–H + Cl2 → H–C–Cl + HCl H H methane chloromethane

H H H Cl C=C + HCl → H–C–C–H H H H H H H H OH C=C + H2O → H–C–C–H IV Addition- involves adding one or more kinds of atoms at the double bond or triple bond of an unsaturated hydrocarbon. H H H Cl C=C + HCl → H–C–C–H H H H H H H H OH C=C + H2O → H–C–C–H H H H H ethanol

B. Hydrogen adds to an unsaturated hydrocarbon A. Addition reactions occur more easily than substitution reactions. Some addition reactions are as fast as ionic reactions. B. Hydrogen adds to an unsaturated hydrocarbon to produce an alkane. The process is called hydrogenation. H H H H C=C + H2 → H–C–C–H H H H H C. Alkynes are more reactive than alkenes.

A. Addition Polymerization- Step 1. H H catalyst H H C=C → •C=C• V Polymerization- The formation of a large molecule by joining smaller molecules (monomers) into a long chain (polymer). There are two types. A. Addition Polymerization- Step 1. H H catalyst H H C=C → •C=C• H H H H ethene monomer (free radical)

Step 2. H H H H H H H H •C=C• + •C=C• → •C–C–C–C• H H H H H H H H Step 3. Step 2 keeps repeating. Ultimately, nC2H4 → (CH2–CH2)n ethylene polyethylene (monomers) (polymer) This process is used to make synthetic rubber, plastics, Teflon, carpeting, etc.

B. Condensation Polymerization- Step 1. HO–R–OH + HO–R’–OH → HO–R–O–R’–OH + H2O Step 2. HO–R–O–R’–OH + HO–R’–OH → HO–R–O–R’–O–R’–OH + H2O This process keeps repeating. This occurs in living organisms to produce proteins and starches, and involves the loss of water (dehydration). It can also be done artificially to produce synthetic fibres (dacron, nylon) and plastics (mylar).

Note: The starting monomer must contain at least two substituted –OH groups.