Presentation on theme: "Chapter 12 Unsaturated Hydrocarbons"— Presentation transcript:
1 Chapter 12 Unsaturated Hydrocarbons 12.1Alkenes and Alkynes
2 Unsaturated Hydrocarbons Have fewer hydrogen atoms attached to the carbon chain than alkanes.Are alkenes with double bonds.Are alkynes with triple bonds.
3 Bond Angles in Alkenes and Alkynes According to VSEPR theory:Three groups in a double bond are bonded at 120° angles.Alkenes are flat: atoms in a C=C lie in the same plane.The groups attached to a triple bond are at 180° angles.
4 Naming Alkenes The names of alkenes Use the corresponding alkane name. Change the ending to ene.Alkene IUPAC CommonH2C=CH2 ethene ethyleneH2C=CH─CH3 propene propylenecyclohexene
5 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.
6 Naming Alkynes The names of alkynes Use the corresponding alkane name. Change the ending to yne.Alkyne IUPAC CommonHC≡CH ethyne acetyleneHC≡C─CH3 propyne
8 Naming Alkenes Write the IUPAC name for CH2=CH─CH2─CH3 and STEP 1 Name the longest carbon chainbuteneSTEP 2 Number the chain from the double bondCH2=CH─CH2─CH3 1-buteneCH3─CH=CH─CH3 2-butene
9 Comparing Names of Alkanes, Alkenes, and Alkynes
10 Naming Alkenes with Substituents CH3│Write the IUPAC name for CH3─CH─CH=CH─CH3STEP 1 Name the longest carbon chain penteneSTEP 2 Number the chain from the double bondCH3─CH─CH=CH─CH penteneSTEP 3 Give the location of each substituent4-methyl- 2-pentene
11 Naming Alkynes with Substituents CH3│Write the IUPAC name for HC≡C─CH─CH3STEP 1 Name the longest carbon chain butyneSTEP 2 Number the chain from the double bond1-butyneSTEP 3 Give the location of each substituent3-methyl-1-butyne
12 Learning Check Write the IUPAC name for each of the following: 1. CH2=CH─CH2─CH32. CH3─CH=CH─CH3CH3|3. CH3─CH=C─CH34. CH3─CC─CH3
13 Solution Write the IUPAC name for each of the following: 1. CH2=CH─CH2─CH butene2. CH3─CH=CH─CH buteneCH3|3. CH3─CH=C─CH methyl-2-butene4. CH3─CC─CH butyne
14 Learning Check Write the structural formula for each of the following: A. 2-pentyneB. 3-methyl-2-pentene
15 Solution Write the structural formula for each of the following: A. CH3─CH2─C≡C─CH pentyneCH3B. CH3─CH2─C=CH─CH3 3-methyl-2-pentene
17 Cis and Trans Isomers In an alkene, cis and trans isomers are possible because the double bondIs rigid.Cannot rotate.Has groups attached to the carbons of the double bond that are fixed relative to each other.CH3 CH CH3CH = CH CH = CHcis trans CH3
18 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.
19 Cis-Trans IsomersCis-trans isomers occur when different groups are attached to the double bond.In a cis isomer, groups on the same side of C=CIn the trans isomer, the groups on opposite sides.
20 Cis-Trans IsomerismCis-trans isomers do not occur if a carbon atom in the double bond is attached to identical groups.Identical Identical2-bromopropene ,1-dibromoethene(not cis or trans) (not cis or trans)HBrHH
21 Naming Cis-Trans Isomers The prefixes cis or trans are placed in front of the alkene name when there are cis-trans isomers.cis transcis-1,2-dibromoethene trans-1,2-dibromoethene
22 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.
23 Learning CheckName each, using cis-trans prefixes when needed.
24 Solution trans-2-butene 1,1-dichloropropene cis-1,2-dibromoethene Identical atoms on one C; no cis or trans
29 Learning CheckWrite an equation for the hydrogenation of 1-butene using a platinum catalyst.
30 Solution Write an equation for the hydrogenation of 1-butene using a platinum catalyst.PtCH2=CH─CH2─CH3 + H2 CH3─CH2─CH2─CH3
31 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 structureIf a label states “partially” or “fully hydrogenated”, the fats contain trans fatty acids.
32 Learning Check(T) True or (F) FalseA. ____ There are more unsaturated fats in vegetable oils.B. ____ Hydrogenation converts some cis-double bonds totrans- double bonds.C. ____ Animal fats have more unsaturated fats.
33 Solution (1) True or (2) False A. T There are more unsaturated fats in vegetable oils.B. T Hydrogenation of oils converts some cis-doublebonds to trans- double bonds.C. F Animal fats have more unsaturated fats.
34 Learning Check Write the product of each the following reactions: Pt CH3─CH=CH─CH3 + H2+ H2
35 SolutionPtCH3─CH=CH─CH3 + H CH3─CH2─CH2─CH3+ H Pt
36 HalogenationIn halogenation, halogen atoms add to the carbon atoms of a double bond or triple bond.
37 Learning Check Write the product of the following addition reactions: 1. CH3─CH=CH─CH3 + Cl22.
38 Solution Write the product of the following addition reactions: Pt 1. CH3─CH=CH─CH3 + Cl2Cl Cll lCH3─CH─CH─CH32.
40 HydrohalogenationIn hydrohalogenation, the atoms of a hydrogen halide add to the carbon atoms of a double bond or triple bond.
41 Markovnikov’s RuleWhen 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 .
42 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 OHH │ │CH3─CH=CH─CH3 + H─OH CH3─CH─CH─CH3
43 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 HH │ │CH3─CH=CH2 + H─OH CH3─CH─CH2(1H) (2H)
44 Learning Check Write the product for the hydration of each of the following:H+1. CH3─CH2─CH=CH─CH2─CH HOHCH3│ H+2. CH3─C=CH─CH2─CH HOHHOH
49 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.
50 PolymerizationIn polymerization, small repeating units called monomers join to form a long chain polymer.monomer unit repeatsn
62 Benzene Structure Benzene Has 6 electrons shared equally among the 6 C atoms.Is also represented as a hexagon with a circle drawn inside.
63 Aromatic Compounds in Nature and Health Vanillin AspirinIbuprofen Acetaminophen
64 Naming Aromatic Compounds Aromatic compounds are namedWith benzene as the parent chain.With one side group named in front of benzene.methylbenzene chlorobenzene
65 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)
66 Aromatic Compounds with Two Groups Two naming systems are used when two groups areattached 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-
67 Aromatic Compounds with Two Groups 3-chlorotoluene ,4-dichlorobenzene chlorophenolm-chlorotoluene p-dichlorobenzene o-chlorophenol
68 Learning Check Select the correct name for each compound: 1) chlorocyclohexane2) chlorobenzene3) 1-chlorobenzene1) 1,2-dimethylbenzene2) m-xylene3) 1,3-dimethylbenzene
75 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.
76 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 byHalogenation chlorine or bromine atomNitration nitro group (—NO2)Sulfonation —SO3H group
77 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.
78 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.
79 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.
80 Learning CheckWrite the equation for the bromination of benzene including catalyst.
81 SolutionWrite the equation for the bromination of benzene including catalyst.