2 Alkenes The Alkenes form another homologous hydrocarbon series Each member contains one double covalent bond between two C atoms.So alkenes are said to be unsaturated.Only 3 atoms joined to each C, not 4General formula = CnH2nWhat was the general formula for the Alkanes?
4 Saturation vs. Unsaturation Simply put, a saturated hydrocarbon has no double bonds between the Carbon atoms (ex. alkanes)Unsaturated has one or more double or triple bonds between carbons (alkenes, alkynes)
5 Physical properties of the Alkenes Very similar to the alkanesInsoluble in watervery soluble in organic solventsLess dense than waterB.P. and M.P increase with increasing carbonAs with alkanes B.P rises about C per carbonHexane b.p. 69 C; 1-Hexene b.p CHeptane b.p. 98 C; 1-Heptene b.p. 93 C
6 Naming Alkenes 1st member is C2H4, ethene. H H C=C Names are derived from the name of the alkane chain with the same number of C atoms.Replace the –ane ending of the alkane name with –ene.1st member is C2H4, ethene.H HC=C
7 Alkene Homologous Series (C1-C2 double bond) EthenePropene1-Butene1-Pentene1-Hexene1-Heptene1-Octene1-Nonene1-DeceneC=CC-C=CC-C-C=CC-C-C-C=CC-C-C-C-C=CC-C-C-C-C-C=CC-C-C-C-C-C-C=CC-C-C-C-C-C-C-C=CC-C-C-C-C-C-C-C-C=C
8 Naming AlkenesLocation of double bond is specified by numbering C atoms in backbone. Give bond the lowest possible number.1-butene (not 4)2-buteneH H HC=C–C–C–HH H H HH H H HH–C–C=C–C–HH HStructural FormulaChemical formulaCondensedStructural formulaC4H8CH2CHCH2CH3C4H8CH3CHCHCH3
9 Naming AlkenesOnce double bond is numbered specify substituents alphabetically by numberUse di, tri and tetra for multiple substituents of the same group2,3-dimethyl-1-buteneC=C–C–CC CStructural Formula(w/o the H)Chemical formulaCondensedStructural formulaC6H12CH2C(CH3)CH(CH3)CH3
10 Problems: Draw the following alkenes: 2-Butene 2–methylpropene 4–Methyl–2-pentene3,3-Dimethyl-1-butene
12 Dienes Alkenes = 1 double bond Dienes have 2 double bonds End in -dieneLocation still denoted by numbersDetermine which way to number the C backbone by assigning the lowest possible number to one of the double bondsExample: 1,3 – pentadienec=c-c=c-cNot 2,4-pentadieneSubstituents are named first[Numbers are separated by commas and the #’s areSeparated from the name by a dashDouble bonds must all be in the backbone.
13 Draw 2-methyl-1,3-heptadiene: Name this compound:C=C-C-C-C=C-CC5-methyl-1,5-heptadieneDraw 2-methyl-1,3-heptadiene:C=C-C=C-C-C-CC
14 AlkynesHomologous series of unsaturated hydrocarbons that contain one triple bond.Each member contains one triple carbon-carbon bond.Alkynes are unsaturated.General formula = CnH2n-2
15 Alkyne Homologous Series (C1-C2 triple bond) EthynePropyne1-Butyne1-Pentyne1-Hexyne1-Heptyne1-Octyne1-Nonyne1-DecyneC CC-C CC-C-C CC-C-C-C CC-C-C-C-C CC-C-C-C-C-C CC-C-C-C-C-C-C CC-C-C-C-C-C-C-C CC-C-C-C-C-C-C-C-C C
16 A common use of one of the alkynes: The Acetylene torch Ethene(Common name)A common use of one of the alkynes:The Acetylene torch
17 Hydrocarbon Table Notice that each Of the hydrocarbon Families differs From the nextBy 2 hydrogenAlkanes share 1pr e-Alkenes share 2pr e-Alkynes share 3pr e-Can you explain howThe above commentsAre related?
18 Naming AlkynesUse the corresponding name from the alkane series and change the –ane to –yne.If necessary, number the carbon atom at which the triple bond occurs with the lowest number.Use the same naming process you used for naming Alkenes
19 H–CC–C–H C3H4 propyne CHCCH3 Structural Chemical Name CondensedFormula Formula Structural formulaH–CC–H C2H2 ethyne CHCHHH–CC–C–H C3H4 propyne CHCCH3H HH–CC–C–C–H C4H6 1-butyne CHCCH2CH3H HH–C–CC–C–H C4H6 2-butyne CH3CCCH3