+ CH 3 C HC 2Cl 2 CH 3 Cl Cl Cl Cl C HC Br Br CH 2 H 2 C Br 2 CH 2 + H 2 C Testing for Unsaturation § When bromine (Br 2 ) is added to an alkane, the red color of bromine persists. +Br 2 +Br 2 § When bromine (Br 2 ) is added to an alkene or alkyne, the red color of bromine disappears immediately.
28 Hydrohalogenation § In hydrohalogenation, the atoms of a hydrogen halide add to the carbon atoms of a double bond or triple bond. Cl H CH 3 CH CH CH 3 + HCl CH 3 CH CH CH 3 Br H + HBr Markovnikov’s Rule § When an unsymmetrical alkene undergoes hydrohalogenation, the H in HX adds to the carbon in the double bond that has the greater number of H atoms . H Cl CH 2 CH CH 3 CH 2 CH CH 3 + HCl Cl H CH 2 CH CH 3 Does not form C with the most H Product that forms
29 Hydration In the addition reaction called hydration an acid H + catalyst is required. § Water (HOH) adds to a double bond. § An H atom bonds to one C in the double bond. § An OH bonds to the other C. H OH H + │ │ CH 3 ─ CH=CH ─ CH 3 + H ─ OH CH 3 ─ CH ─ CH ─ CH 3 When hydration occurs with a double bond that has an unequal number of H atoms, § The H atom bonds to the C in the double bond with the most H. § The OH bonds to the C in the double bond with the fewest H atoms. OH H H + │ │ CH 3 ─ CH=CH 2 + H ─ OH CH 3 ─ CH ─ CH 2 ( 1H ) ( 2H )
30 Polymerization of Alkenes Polymers are § Large, long-chain molecules. § Found in nature, including cellulose in plants, starches in food, proteins and DNA in the body. § Also synthetic such as polyethylene and polystyrene, Teflon, and nylon. § Made up of small repeating units called monomers. § Made by reaction of small alkenes. § In polymerization, small repeating units called monomers join to form a long chain polymer.
31 Benzene has 6 electrons shared equally among the 6 C atoms. § Is also represented as a hexagon with a circle drawn inside. 12.8 Aromatic Compounds Aromatic Compounds in Nature and Health COH O O C O CH 3 CH O OCH 3 OH CH CH 3 COH O CH 2 CH 3 CH H 3 C OH NH O C CH 3 Vanillin Aspirin Ibuprofen Acetaminophen
32 Naming Aromatic Compounds Aromatic compounds are named with benzene as the parent chain . § With one side group named in front of benzene. Some substituted benzene rings have common names are still used. § With a single substituent use a common name or are named as a benzene derivative . methylbenzene CH 3 Cl chlorobenzene
33 Aromatic Compounds with Two Groups Two naming systems are used when two groups are attached to a benzene ring. § Number the ring to give the lowest numbers to the side groups. § Use prefixes to show the arrangement: ortho(o-) for 1,2- meta(m-) for 1,3- para(p-) for 1,4- OH Cl CH 3 Cl Cl Cl 2-chlorophenol o-chlorophenol 1,4-dichlorobenzene p-dichlorobenzene 3-chlorotoluene m-chlorotoluene
- Fall '10
- Atom, Organic compound, Chemical bond