3AlkenesStructure:The VSEPR model predicts bond angles of 120° about each carbon of a double bond.
4Alkenes CIS TRANS Cis-trans isomerism because of restricted rotation about a carbon-carbon double bond, an alkene with two different groups on each carbon of the double bond shows cis-trans isomerism.CISTRANS
6Naming AlkenesStep 1: Name the longest chain that contains the C=C bond. Use the IUPAC root and the –ene ending.Step 2: Number the longest chain so the C=C bond gets the lowest number possible.Step 3: Designate the C=C bond in the name with the lowest-numbered carbon.
11Cycloalkenes To name a cycloalkene: number the carbon atoms of the ring double bond 1 and 2 in the direction that gives the lower number to the substituent encountered first.number and list substituents in alphabetical order.
13Physical Properties Alkenes and alkynes are nonpolar compounds. The only attractive forces between their molecules are London dispersion forces.Their physical properties are similar to those of alkanes with the same carbon skeletons.Alkenes and alkynes are insoluble in water but soluble in one another and in nonpolar organic liquids.
14Alkene Reactions Alkenes are quite chemically reactive Many reactions are addition reactions:
15Reactions of Alkenes The most common reaction is addition hydrohalogenationhalogenation
16Alkene Reactions, cont.Hydrogenation (addition) reactions can occur in the presence of a catalyst (Pt, Pd, or Ni).The hydrogenation of vegetable oils is an important commercial process.
17Addition of H2Virtually all alkenes add H2 in the presence of a transition metal catalyst, commonly Pd, Pt, or Ni.
18Addition of a Halogen (Halogenation) Addition takes place readily at room temp.reaction is generally carried out using pure reagents, or mixing them in a nonreactive organic solventaddition of Br2 is a useful qualitative test for the presence of a carbon-carbon double bond
19Addition of HX (Hydrohalogenation) Addition of HX (HCl, HBr, or HI) to an alkeneH adds to one carbon of the C=C and X to the other.Markovnikov’s rule: H adds to the less substituted carbon and X to the more substituted carbon.
25PolymerizationShow the structure of a polymer by placing parentheses around the repeating monomer unit.Place a subscript, n, outside the parentheses to indicate that this unit repeats n times.The structure of a polymer chain can be reproduced by repeating the enclosed structure in both directions.following a section of polypropene (polypropylene)