Chapter 11 Unsaturated Hydrocarbons 11.1 Alkenes and Alkynes Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Unsaturated Hydrocarbons Have fewer hydrogen atoms attached to the carbon chain than alkanes. Are alkenes with double bonds. Are alkynes with triple bonds. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Bond Angles in Alkenes and Alkynes According to VSEPR theory: Three groups in a double bond are bonded at 120° angles. Alkenes are flat, because the atoms in a double bond lie in the same plane. The groups attached to a triple bond are at 180° angles.

Physical properties Similar to alkanes Solubility Soluble in nonpolar solvents Not soluble in water Low density, boiling point and melting point Properties vary based on chain size Interesting physical property. Alkenes with several double bonds will have a color associated with them.

Colored alkenes lycopene - red of tomato, paprika and watermelon CH 3 H C lycopene - red of tomato, paprika and watermelon CH 3 H C -carotene, yellow of carrots and yams

Naming Alkenes The names of alkenes Use the corresponding alkane name. Change the ending to ­ene. Alkene IUPAC Common H2C=CH2 ethene ethylene H2C=CH─CH3 propene propylene cyclohexene

Ethene (ethylene) Ethene or ethylene Is an alkene C2H4. Has two carbon atoms connected by a double bond. Has two H atoms bonded to each C atom. Is flat with all the C and H atoms in the same plane. Is used to accelerate the ripening of fruits. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Naming Alkynes The names of alkynes Use the corresponding alkane name. Change the ending to ­yne. Alkyne IUPAC Common HC≡CH ethyne acetylene HC≡C─CH3 propyne

Guide to Naming Alkenes and Alkynes Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Naming Alkenes Write the IUPAC name for CH2=CH─CH2─CH3 and STEP 1 Name the longest carbon chain butene STEP 2 Number the chain from the double bond CH2=CH─CH2─CH3 1-butene 1 2 3 4 CH3─CH=CH─CH3 2-butene

Comparing Names of Alkanes, Alkenes, and Alkynes TABLE 12.1 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Naming Alkenes with Substituents CH3 │ Write the IUPAC name for CH3─CH─CH=CH─CH3 STEP 1 Name the longest carbon chain pentene STEP 2 Number the chain from the double bond CH3─CH─CH=CH─CH3 2-pentene 5 4 3 2 1 STEP 3 Give the location of each substituent 4-methyl- 2-pentene

Naming Alkynes with Substituents CH3 │ Write the IUPAC name for HC≡C─CH─CH3 1 2 3 4 STEP 1 Name the longest carbon chain butyne STEP 2 Number the chain from the double bond 1-butyne STEP 3 Give the location of each substituent 3-methyl-1-butyne

Learning Check Write the IUPAC name for each of the following: 1. CH2=CH─CH2─CH3 2. CH3─CH=CH─CH3 CH3 | 3. CH3─CH=C─CH3 4. CH3─CC─CH3

Solution Write the IUPAC name for each of the following: 1. CH2=CH─CH2─CH3 1-butene 2. CH3─CH=CH─CH3 2-butene CH3 | 3. CH3─CH=C─CH3 2-methyl-2-butene 4. CH3─CC─CH3 2-butyne

Learning Check Write the structural formula for each of the following: A. 2-pentyne B. 3-methyl-2-pentene

Solution Write the structural formula for each of the following: A. CH3─CH2─C≡C─CH3 2-pentyne CH3  B. CH3─CH2─C=CH─CH3 3-methyl-2-pentene

Chapter 12 Unsaturated Hydrocarbons 12.2 Cis-Trans Isomers Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Cis-Trans Isomers Cis-trans isomers occur when different groups are attached to the double bond. In a cis isomer, groups on the same side of C=C In the trans isomer, the groups on opposite sides.

Cis-Trans Isomers Cis-trans isomers Can be modeled by making a “double bond” with your fingers with both thumbs on the same side or opposite from each other. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Cis-Trans Isomers Cis-trans isomers occur when different groups are attached to the double bond. In a cis isomer, groups are attached on the same side of the double bond. In the trans isomer, the groups are attached on opposite sides. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Cis-Trans Isomerism Cis-trans isomers do not occur if a carbon atom in the double bond is attached to identical groups. Identical Identical 2-bromopropene 1,1-dibromoethene (not cis or trans) (not cis or trans) H Br H H

Naming Cis-Trans Isomers The prefixes cis or trans are placed in front of the alkene name when there are cis-trans isomers. cis trans cis-1,2-dibromoethene trans-1,2-dibromoethene

Pheromones A pheromone Is a chemical messenger emitted by insects in tiny quantities. Called bombykol emitted by the silkworm moth to attract other moths has one cis and one trans double bond. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check Name each, using cis-trans prefixes when needed.

Solution trans-2-butene 1,1-dichloropropene cis-1,2-dibromoethene Identical atoms on one C; no cis or trans

Chapter 12 Unsaturated Hydrocarbons 12.3 Addition Reactions Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Addition Reactions In addition reactions, Reactants add to the carbon atoms in double or triple bonds. A double or triple bond is easily broken, which makes them very reactive. TABLE 12.2 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Hydrogenation In hydrogenation, Hydrogen atoms add to the carbon atoms of a double bond or triple bond. A catalyst such as Pt or Ni is used to speed up the reaction.

Hydrogenation of Oils Adding H2 to double bonds in vegetable oils produces Compounds with higher melting points. Solids at room temperature such as margarine, soft margarine, and shortening. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check Write an equation for the hydrogenation of 1-butene using a platinum catalyst.

Solution Write an equation for the hydrogenation of 1-butene using a platinum catalyst. Pt CH2=CH─CH2─CH3 + H2 CH3─CH2─CH2─CH3

Trans Fats In vegetable oils, the unsaturated fats usually contain cis double bonds. During hydrogenation, some cis double bonds are converted to trans double bonds (more stable) causing a change in the fatty acid structure If a label states “partially” or “fully hydrogenated”, the fats contain trans fatty acids.

Learning Check (T) True or (F) False A. ____ There are more unsaturated fats in vegetable oils. B. ____ Hydrogenation converts some cis-double bonds to trans- double bonds. C. ____ Animal fats have more unsaturated fats.

Solution (1) True or (2) False A. T There are more unsaturated fats in vegetable oils. B. T Hydrogenation of oils converts some cis-double bonds to trans- double bonds. C. F Animal fats have more unsaturated fats.

Learning Check Write the product of each the following reactions: Pt CH3─CH=CH─CH3 + H2 + H2

Solution Pt CH3─CH=CH─CH3 + H2 CH3─CH2─CH2─CH3 + H2 Pt

Halogenation In halogenation, halogen atoms add to the carbon atoms of a double bond or triple bond.

Learning Check Write the product of the following addition reactions: 1. CH3─CH=CH─CH3 + Cl2 2.

Solution Write the product of the following addition reactions: Pt 1. CH3─CH=CH─CH3 + Cl2 Cl Cl l l CH3─CH─CH─CH3 2.

Testing for Unsaturation Br2 When bromine (Br2) is added to an alkane, the red color of bromine persists. When bromine (Br2) is added to an alkene or alkyne, the red color of bromine disappears immediately. Br2 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 15

Hydrohalogenation In hydrohalogenation, the atoms of a hydrogen halide add to the carbon atoms of a double bond or triple bond.

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 .

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+ │ │ CH3─CH=CH─CH3 + H─OH CH3─CH─CH─CH3

Hydration 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+ │ │ CH3─CH=CH2 + H─OH CH3─CH─CH2 (1H) (2H)

Learning Check Write the product for the hydration of each of the following: H+ 1. CH3─CH2─CH=CH─CH2─CH3 + HOH CH3 │ H+ 2. CH3─C=CH─CH2─CH3 + HOH 3. + HOH

Solution H OH │ │ 1. CH3─CH2─CH─CH─CH2─CH3 CH3 │ 2. CH3─C─CH─CH2─CH3 │ │ 1. CH3─CH2─CH─CH─CH2─CH3 CH3 │ 2. CH3─C─CH─CH2─CH3 │ │ OH H OH 3. H

Learning Check Write the products of each reaction.

Solution

Chapter 12 Unsaturated Hydrocarbons 12.4 Polymers of Alkenes Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Polymers 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.

Polymerization In polymerization, small repeating units called monomers join to form a long chain polymer. monomer unit repeats n

Common Synthetic Polymers Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Polymers from Addition Reactions TABLE 12.3 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

More Monomers and Polymers Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check What is the starting monomer for polyethylene?

Solution Ethene (ethylene) CH2=CH2

Learning Check Name the monomer used to make Teflon and write a portion of a Teflon polymer using four monomers.

Solution F─C=C─F tetrafluoroethene F F │ │ F F F F F F F F │ │ F─C=C─F tetrafluoroethene F F F F F F F F │ │ │ │ │ │ │ │ ─C─C─C─C─C─C─C─C─ portion of Teflon

Recycling Plastics Recycling is simplified by using codes found on plastic items. 1 PETE Polyethyleneterephtalate 2 HDPE High-density polyethylene 3 PV Polyvinyl chloride 4 LDPE Low-density polyethylene 5 PP Polypropylene 6 PS Polystyrene Copyright © 2007 by Pearson Education, Inc . Publishing as Benjamin Cummings

Learning Check What types of plastic are indicated by the following codes? A. B. C. 3 PV 5 PP 6 PS

Solution What types of plastic are indicated by the following codes? A. Polyvinyl chloride B. Polypropylene C. Polystyrene . 3 PV 5 PP 6 PS

Chapter 12 Unsaturated Hydrocarbons 12.5 Aromatic Compounds Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Benzene Structure Benzene Has 6 electrons shared equally among the 6 C atoms. Is also represented as a hexagon with a circle drawn inside. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Aromatic Compounds in Nature and Health Vanillin Aspirin Ibuprofen Acetaminophen

Naming Aromatic Compounds Aromatic compounds are named With benzene as the parent chain. With one side group named in front of benzene. methylbenzene chlorobenzene

Some Common Names Some substituted benzene rings Have common names used for many years. With a single substituent use a common name or are named as a benzene derivative. toluene aniline phenol (methylbenzene) (benzenamine) (hydroxybenzene)

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-

Aromatic Compounds with Two Groups 3-chlorotoluene 1,4-dichlorobenzene 2-chlorophenol m-chlorotoluene p-dichlorobenzene o-chlorophenol

Learning Check Select the correct name for each compound: 1) chlorocyclohexane 2) chlorobenzene 3) 1-chlorobenzene 1) 1,2-dimethylbenzene 2) m-xylene 3) 1,3-dimethylbenzene

Solution 2) chlorobenzene 2) m-xylene 3) 1,3-dimethylbenzene

Learning Check Write the structural formulas for each of the following: A. 1,3-dichlorobenzene B. o-chlorotoluene

Solution A. 1,3-dichlorobenzene B. o-chlorotoluene

Learning Check Identify the organic family for each: A. CH3─CH2─CH=CH2 B. C. CH3─C≡CH D.

Solution Identify the organic family for each: A. CH3─CH2─CH=CH2 alkene B. cycloalkane (alkane) C. CH3─C≡CH alkyne D. aromatic

Chapter 12 Unsaturated Hydrocarbons 12.6 Properties of Aromatic Compounds Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Properties of Aromatic Compounds Have a stable aromatic bonding system. Are resistant to many reactions. Undergo substitution reactions, which retain the stability of the aromatic bonding system.

Substitution Reactions In a substitution reaction, a hydrogen atom on a benzene ring is replaced by an atom or group of atoms. Type of substitution H on benzene replaced by Halogenation chlorine or bromine atom Nitration nitro group (—NO2) Sulfonation —SO3H group

Halogenation In a halogenation An H atom of benzene is replaced by a chlorine or bromine atom. A catalyst such as FeCl3 is needed in chlorination. A catalyst such as FeBr3 is needed in bromination.

Nitration In the nitration of benzene An H atom of benzene is replaced by a nitro (-NO2) group from HNO3. An acid catalyst such as H2SO4 is needed.

Sulfonation In a sulfonation An H atom on benzene is replaced by a —SO3H group from SO3. An acid catalyst such as H2SO4 is needed.

Learning Check Write the equation for the bromination of benzene including catalyst.

Solution Write the equation for the bromination of benzene including catalyst.