- Alkenes
- Alkynes
Alkenes
 Each
member contains one double covalent
bond between two C atoms.

So alkenes are said to be unsaturated.
 General
formula = CnH2n
Naming Alkenes

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
H
C=C
H
H
Alkene Homologous Series
(C1-C2 double bond)









Ethene
Propene
1-Butene
1-Pentene
1-Hexene
1-Heptene
1-Octene
1-Nonene
1-Decene
C=C
C-C=C
C-C-C=C
C-C-C-C=C
C-C-C-C-C=C
C-C-C-C-C-C=C
C-C-C-C-C-C-C=C
C-C-C-C-C-C-C-C=C
C-C-C-C-C-C-C-C-C=C
Naming Alkenes
 Location
of double bond is specified by
numbering C atoms in backbone.
 Give bond the lowest possible number.
H
HH
C=C–C–C–H
H H H H
1-butene (not 4)
H H HH
H–C–C=C–C–H
H
H
2-butene
Naming Alkenes

Once double bond is numbered specify branches
alphabetically by number

Use di, tri and tetra for multiple branches of the
same group
CH2= C–CH–CH3
CH3 CH3
Naming Alkynes

Use 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

General formula = CnH2n-2
Alkynes

Homologous series of unsaturated
hydrocarbons that contain one triple
bond.
General formula = CnH2n-2
Alkyne Homologous Series
(C1-C2 triple bond)






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

Ethyne
Propyne
1-Butyne
1-Pentyne
1-Hexyne
1-Heptyne
1-Octyne
1-Nonyne
1-Decyne
C C
C-C C
C-C-C C
C-C-C-C C
C-C-C-C-C C
C-C-C-C-C-C C
C-C-C-C-C-C-C C
C-C-C-C-C-C-C-C C
C-C-C-C-C-C-C-C-C C
Problems:

Draw the following




4–methyl–2-pentene
3-ethyl-1-pentyne
3,3-dimethyl-1-butene
2–methylpropene
• *why is there no number to state the location of this
double bond?
Name this Compound:
4-ethyl-5-methyl-4-octene
Can you name this compound?
3-ethyl-1-pentyne
Functional Groups
Carbon can make bonds with atoms other than
carbon or hydrogen.
These are called “Functional groups”
Organic Halides

One or more of the hydrogen atoms is replaced with a
halogen
 F, Cl, Br, or I

Not hydrocarbons! Often called halocarbons.
Naming Organic Halides
Use prefixes to specify substituent:

fluoro, chloro, bromo, iodo

If more than one, use di, tri, etc. to specify # of
substituents.

If necessary, give locations by numbering C-atoms in
backbone so that the halide has the lowest number.
CH3-CH-CH-CH2-CH3
2,3-dibromopentane
Br
Br
Naming Halides
H
H–C–Cl
H
Chloromethane
“Chloroform”
H H H
H–C–C–C–H
H F H
2-fluoropropane
Name the following Compound:
CH3CCl2CHClCH3
H Cl H H
H–C–C–C–C–H
H Cl Cl H
2,2,3-trichlorobutane
C4H7Cl3
Name this compound:
3-Bromo-2-Iodopentane
Name this compound:
F
H-C
F
Cl
1,1-dicloro-2,2-difluoroethane
Cl
One of the “freons”
C-H
Dienes





Alkenes = 1 double
Example: 1,3 – pentadiene
bond
c=c-c=c-c
Dienes have 2 double
bonds
Not 2,4-pentadiene
End in -diene
Location still denoted
Substituents are named first
by numbers
Determine which way
[Numbers are separated by
to number the C
commas and the #’s are
backbone by assigning
separated from the name
the lowest possible
by a dash]
number to one of the
Double bonds must all be in the backbone.
double bonds
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
Hydrocarbon Table
Notice that each
Of the hydrocarbon
Families differs
From the next
By 2 hydrogen
Alkanes share 1pr eAlkenes share 2pr eAlkynes share 3pr eCan you explain how
The above comments
Are related?
Structural
Formula
Chemical
Formula
Name
Condensed
Structural formula
H–CC–H
C2H2
ethyne
CHCH
H
H–CC–C–H
H
C3H4
propyne
CHCCH3
HH
H–CC–C–C–H
HH
C4H6
1-butyne
CHCCH2CH3
H
H
H–C–CC–C–H
H
H
C4H6
2-butyne
CH3CCCH3