2 Unsaturated Hydrocarbons do not contain the maximum number of hydrogen atoms that could be attached to each carbon atom.are alkenes when they contain double C=C bonds.are alkynes when they contain triple C≡C bonds.react with hydrogen gas to form saturated hydrocarbons.
3 AlkenesAlkenescontain a carbon–carbon double bond that forms when adjacent carbon atoms share two pairs of valence electrons.are flat because the atoms in a double bond lie in the same plane.have a trigonal planar arrangement around the double bonded carbon atoms.
4 AlkynesAlkyneshave a triple bond that forms when two carbon atoms share three pairs of valence electrons.have a 180˚ angle and are linear.
6 Naming Alkenes and Alkynes Write the IUPAC name for the following.A B.Step 1 Name the longest carbon chain that containsthe double or triple bond.Analyze the Problem.Functional GroupClassIUPACNamingNameA. Double bondAlkeneReplace –ane of alkane with –eneB. Triple bondAlkyneReplace –ane of alkane with –yne
7 Naming Alkenes and Alkynes Write the IUPAC name for the following.A B.Step 1 Name the longest carbon chain that containsthe double or triple bond.A B.butene heptyne
8 Naming Alkenes and Alkynes Write the IUPAC name for the following.A B.Step 2 Number the carbon chain from the end nearerthe double or triple bond.A B.2−butene −heptyne
9 Naming Alkenes and Alkynes Write the IUPAC name forA B.Step 3 Give the location and name of eachsubstituent (alphabetical order) as a prefix tothe alkene or alkyne name.A B.2−butene methyl−2−heptyne
10 Naming Cycloalkenes When naming a cycloalkene, if there are no substituents, the double bond does not need a number.if there is a substituent, the carbons in the double bond are numbered as 1 and 2, and the ring is numbered from carbon 2 in the direction that will give the lower number to the substituent.cyclopentene methylcyclohexane
11 Cis and Trans Isomers Cis and trans isomers have the same formula, but different physical and chemical properties.occur because double bonds in alkenes are rigid and cannot rotate.We add the prefix cis or trans to denote whether the atoms bonded to the carbon atoms are on the same side or the opposite sides of the double bond.
12 Cis–Trans Isomers Cis–trans isomers occur when different groups are attached to the carbon atoms in a 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 of the double bond.
13 Cis–Trans IsomerismCis–trans isomers do not occur if one of the carbonatoms in the double bond has identical groups.(neither cis nor trans) (neither cis nor trans)
14 Naming Cis–Trans Isomers The prefixes cis- or trans- are placed in front of thealkene name when there are cis–trans isomers.cis trans-cis-1,2-Dibromoethene trans-1,2-Dibromoethene
15 Alkenes: Drawing Cis–Trans Isomers Draw the cis and trans isomers of 2-hexene.
16 Learning CheckName each, using cis–trans prefixes when needed.A.
17 Solution Name each, using cis–trans prefixes when needed. cis-1,2-Dibromoethenetrans-2-Butene1,1-DichloropropeneA.A.Identical atoms; no cis or trans
18 Addition ReactionsThere are different addition reactions as shown in Table 12.2.
19 Hydrogenation In hydrogenation, hydrogen atoms add to the carbon atoms of a double or triple bond.a catalyst, such as Pt, Pd or Ni, is used to speed up the reaction.
20 Halogenation Halogenation reactions of alkenes and alkynes occur rapidly without a catalyst.
21 Hydrohalogenation Hydrohalogenation reactions occur in two steps.
22 Markovnikov’s RuleIn assymetrical alkenes, the H in HX adds to the carbon in the double bond that has the greater number of H atoms.
23 Hydration In hydration, a strong acid (H+) catalyst is required. water (HOH) adds to a double bond.an −H atom bonds to one C in the double C═C bond.an −OH bonds to the other C.
24 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 C═C bond that has more hydrogen atoms.the −OH bonds to the C in the double C═C bond that has the fewer hydrogen atoms.
25 PolymersPolymers arelarge, molecules that consist of small repeating units called monomers.found in nature, including cellulose in plants, starches in food, and proteins and DNA in the body.also made synthetically, such as polyethylene and polystyrene, Teflon, and nylon.often made by reaction of small alkenes at high temperature and pressure.
26 PolymerizationIn polymerization, small repeating units called monomers join to form a long chain polymer.
30 Recycling PlasticsRecycling is simplified by using codes found on plasticitems.
31 Benzene Structure Benzene has 6 electrons shared equally among the 6 C atoms.behaves more like an alkane; it does not undergo addition reactions.is also represented as a hexagon with a circle drawn inside.
32 Aromatic CompoundsAt the time of its discovery, many compounds containing benzene had fragrant odors, so the family of benzene compounds became known as aromatic compounds.
34 Naming Aromatic Compounds Aromatic compounds are namedwith benzene as the parent chain.with one side group named in front of benzene.Methylbenzene Chlorobenzene
35 Some Common Names Some substituted benzene rings have common names that have been used for many years.with a single substituent use a common name or are named as a benzene derivative.
36 Aromatic Compounds with Two Groups When two groups are attached to a benzene ring,number the ring to give the lowest numbers to the side groups (IUPAC),oruse prefixes to show the arrangement of the substituents (common) on the ring, as shown below.ortho (o) for 1,2-meta (m) for 1,3-para (p) for 1,4-
37 Aromatic Compounds with Two Substituents 3-Chlorotoluene ,4-Dichlorobenzene Chlorophenol(m-chlorotoluene) (p-dichlorobenzene) (o-chlorophenol)Substituents on1st and 3rd carbons 1st and 4th carbons 1st and 2nd carbons
38 XyleneFor isomers of dimethylbenzene, the common name, xylene may be used.
39 Aromatic Compounds with Three Substituents 1,3,5-Trichlorobenzene 2,6-Dibromo-4-chlorotoluene 4-Bromo-2-chlorotoluene
40 Properties of Aromatic Compounds have higher melting and boiling points due to the flat symmetrical structure of the rings.are not soluble in water unless they contain–OH or –COOH substituents.have a stable aromatic bonding system.are resistant to many reactions that break up the aromatic system.are flammable like other hydrocarbons.