Transcript - Alkenes / Dienes - Alkynes

- Alkenes / Dienes
- Alkynes
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 4
 General

formula = CnH2n
What was the general formula for the Alkanes?
Saturated vs Unsaturated
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)
H
H
H
C
H
H
C
C
H
H
C
CH3(CH2)2CH3
H
H
H
CH
CH3
CH
CH3
C
H3C
C
CH3
Physical 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 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.
1-butene (not 4)
H
HH
C=C–C–C–H
H H H H
2-butene
H H HH
H–C–C=C–C–H
H
H
Structural Formula
C4H8
C4H8
Chemical formula
CH2CHCH2CH3
CH3CHCHCH3
Condensed
Structural formula
Naming Alkenes

Once double bond is numbered specify
substituents alphabetically by number

Use di, tri and tetra for multiple substituents of the
same group
2,3-dimethyl-1-butene
C=C–C–C
C C
Structural Formula
(w/o the H)
C6H12
Chemical formula
CH2C(CH3)CH(CH3)CH3
Condensed
Structural formula
Problems:

Draw the following alkenes:




2-Butene
2–methylpropene
4–Methyl–2-pentene
3,3-Dimethyl-1-butene
Name this Compound:
4-ethyl-5-methyl-4-octene
Dienes





Alkenes = 1 double
Example: 1,3 – pentadiene
bond
c=c-c=c-c
Dienes have 2 double
Not 2,4-pentadiene
bonds
End in -diene
Substituents are named first
Location still denoted
by numbers
[Numbers are separated by
Determine which way
commas and the #’s are
to number the C
backbone by assigning Separated from the name by a
dash
the lowest possible
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
Alkynes

Homologous series of unsaturated
hydrocarbons that contain one triple
bond.

Each member contains one triple
carbon-carbon bond.


Alkynes are unsaturated.
General formula = CnH2n-2
Alkyne Homologous Series
(C1-C2 triple bond)









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
Ethene
(Common name)
A common use of one of the alkynes:
The Acetylene torch
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?
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
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
Can you name this compound?
3-ethyl-1-pentyne