Alkenes and Alkynes
Geometric Isomers of Alkenes
Addition Reactions
 Saturated compounds (alkanes) have
the maximum number of hydrogen
atoms attached to each carbon atom
 Unsaturated compounds have fewer
hydrogen atoms attached to the carbon
chain than alkanes
 Unsaturated compounds contain double
or triple bonds
 Carbon-carbon double bonds
 Names end in -ene
 H2C=CH2
ethene (ethylene)
 H2C=CH-CH3
propene (propylene)
 cyclohexene
 Carbon-carbon triple bonds
 Names end in -yne
 HC
CH
 HC C-CH3
ethyne(acetylene)
propyne
 When the carbon chain has 4 or more C atoms,
number the chain to give the lowest number to
the double or triple bond.
1
2 3 4
CH2=CHCH2CH3
1-butene
CH3CH=CHCH3
2-butene
CH3CH CHCH3
2-butyne
 Write the IUPAC name for each of the following
unsaturated compounds:
 CH3CH2C CCH3
2-pentyne
CH3
 CH3C=CHCH3
2-methyl-2-butene
3-methylcyclopentene
 Double bond is fixed
 Cis/trans Isomers are possible
 Adds a hydrogen atom to each carbon atom of a
double bond
H H
Ni
HH
 H–C=C–H + H2  H–C–C–H
HH
ethene
ethane
 Adding H2 to vegetable oils produces compounds
with higher melting points
 Margarines
 Soft margarines
 Shortenings (solid)