- Alkenes / Dienes- Alkynes

AlkenesAlkenes The Alkenes form another The Alkenes form another homologous homologous

hydrocarbon serieshydrocarbon series

Each member contains Each member contains oneone double covalent double covalent bond between two C atoms.bond between two C atoms. So alkenes are said to be So alkenes are said to be unsaturatedunsaturated.. Only 3 atoms joined to each C, not 4Only 3 atoms joined to each C, not 4

General formula = General formula = CCnnHH2n2n

What was the general formula for the Alkanes?What was the general formula for the Alkanes?

Saturated vs UnsaturatedSaturated vs Unsaturated

Saturation vs. UnsaturationSaturation vs. Unsaturation Simply put, a saturated Simply put, a saturated

hydrocarbon has no hydrocarbon has no double bonds between double bonds between the Carbon atoms (ex. the Carbon atoms (ex. alkanes)alkanes)

Unsaturated has Unsaturated has one or one or moremore double or triple double or triple bonds between carbons bonds between carbons (alkenes, alkynes)(alkenes, alkynes)

CC C

C

H

H

H

H

HH

H

H

H

H

CH3(CH2)2CH3

CH

CH3 CH

CH3

CH3C C

CH3

Physical properties of the AlkenesPhysical properties of the Alkenes

-Very similar to the alkanes

- Insoluble in water- very soluble in organic solvents

- Less dense than water

- B.P. and M.P increase with increasing carbon- As with alkanes B.P rises about 20-30 C per carbon- Hexane b.p. 69 C; 1-Hexene b.p. 63.5 C- Heptane b.p. 98 C; 1-Heptene b.p. 93 C

Naming AlkenesNaming Alkenes Names are derived from the name of the alkane Names are derived from the name of the alkane

chain with the same number of C atoms.chain with the same number of C atoms.

Replace the –ane ending of the alkane name Replace the –ane ending of the alkane name with –ene.with –ene.

1st member is C2H4, ethene.H HH H

CC=C=C H H H H

Alkene Homologous SeriesAlkene Homologous Series(C1-C2 double bond)(C1-C2 double bond)

EtheneEthene PropenePropene 1-Butene1-Butene 1-Pentene1-Pentene 1-Hexene1-Hexene 1-Heptene1-Heptene 1-Octene1-Octene 1-Nonene1-Nonene 1-Decene1-Decene

C=CC=CC-C=CC-C=CC-C-C=CC-C-C=CC-C-C-C=CC-C-C-C=CC-C-C-C-C=CC-C-C-C-C=CC-C-C-C-C-C=CC-C-C-C-C-C=CC-C-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=CC-C-C-C-C-C-C-C-C=CC-C-C-C-C-C-C-C-C=C

Naming AlkenesNaming Alkenes Location of double bond is specified by Location of double bond is specified by

numbering C atoms in backbone. Give numbering C atoms in backbone. Give bond the lowest possible number.bond the lowest possible number.

H H H C=C–C–C–HH H H H

C4H8

CH2CHCH2CH3

H H H HH–C–C=C–C–H H H

C4H8

CH3CHCHCH3

1-butene (not 4) 2-butene

Structural Formula

Chemical formula

CondensedStructural formula

Naming AlkenesNaming Alkenes Once double bond is numbered specify Once double bond is numbered specify

substituents alphabetically by numbersubstituents alphabetically by number

Use di, tri and tetra for multiple substituents of the Use di, tri and tetra for multiple substituents of the same groupsame group

C=C–C–C C C

C6H12

CH2C(CH3)CH(CH3)CH3

Structural Formula(w/o the H)

Chemical formula

CondensedStructural formula

2,3-dimethyl-1-butene

Problems:Problems: Draw the following alkenes:Draw the following alkenes:

2-Butene2-Butene 2–methylpropene2–methylpropene 4–Methyl–2-pentene4–Methyl–2-pentene 3,3-Dimethyl-1-butene3,3-Dimethyl-1-butene

Name this Compound:

4-ethyl-5-methyl-4-octene

DienesDienes Alkenes = 1 double bondAlkenes = 1 double bond Dienes have 2 double Dienes have 2 double

bondsbonds End in -dieneEnd in -diene Location still denoted by Location still denoted by

numbersnumbers Determine which way to Determine which way to

number the C backbone number the C backbone by assigning the lowest by assigning the lowest possible number to one possible number to one of the double bondsof the double bonds

Example: 1,3 – Example: 1,3 – pentapentadienedienec=c-c=c-cc=c-c=c-cNot 2,4-pentadieneNot 2,4-pentadiene

Substituents are named firstSubstituents are named first

[Numbers are separated by [Numbers are separated by commas and the #’s are commas and the #’s are

Separated from the name by a Separated from the name by a dashdash

Double bonds must all be in the backbone.

Name this compound:

C=C-C-C-C=C-C C

5-methyl-1,5-heptadiene

Draw 2-methyl-1,3-heptadiene:

C=C-C=C-C-C-C C

AlkynesAlkynes Homologous series of unsaturated Homologous series of unsaturated

hydrocarbons that contain one triple hydrocarbons that contain one triple bond.bond.

Each member contains one triple carbon-Each member contains one triple carbon-carbon bond.carbon bond.

Alkynes are unsaturated.Alkynes are unsaturated.

General formula = CGeneral formula = CnnHH2n-22n-2

Alkyne Homologous SeriesAlkyne Homologous Series(C1-C2 triple bond)(C1-C2 triple bond)

EthyneEthyne PropynePropyne 1-Butyne1-Butyne 1-Pentyne1-Pentyne 1-Hexyne1-Hexyne 1-Heptyne1-Heptyne 1-Octyne1-Octyne 1-Nonyne1-Nonyne 1-Decyne1-Decyne

C CC CC-C CC-C CC-C-C CC-C-C CC-C-C-C CC-C-C-C CC-C-C-C-C CC-C-C-C-C CC-C-C-C-C-C CC-C-C-C-C-C CC-C-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 CC-C-C-C-C-C-C-C-C CC-C-C-C-C-C-C-C-C C

Ethene

(Common name)

A common use of one of the alkynes:The Acetylene torch

Hydrocarbon TableHydrocarbon Table

Notice that eachOf the hydrocarbonFamilies differsFrom the next By 2 hydrogen

Alkanes share 1pr e-

Alkenes share 2pr e-

Alkynes share 3pr e-

Can you explain howThe above commentsAre related?

Naming AlkynesNaming Alkynes Use the corresponding name from the alkane Use the corresponding name from the alkane

series and change the –ane to –yne.series and change the –ane to –yne.

If necessary, number the carbon atom at which If necessary, number the carbon atom at which the triple bond occurs with the lowest number.the triple bond occurs with the lowest number.

Use the same naming process you used for Use the same naming process you used for naming Alkenesnaming Alkenes

H–CC–H C2H2 ethyne CHCH

HH–CC–C–H C3H4 propyne CHCCH3

H

H HH–CC–C–C–H C4H6 1-butyne CHCCH2CH3

H H

H HH–C–CC–C–H C4H6 2-butyne CH3CCCH3

H H

Structural Chemical Name CondensedFormula Formula Structural formula

Can you name this compound?

3-ethyl-1-pentyne