Topic: Naming Alkanes
Do Now: Draw the possible bonds a single
carbon atom can have if it has a bonding
capacity of 4
Alkanes (CnH2n+2)
C3H8
Chemical
Formula
CH3CH2CH3
Condensed Structural
Formula
H H H
H–C–C–C–H
H H H
Structural
Formula
straight-chain alkane
C4H10
H H H H
H–C–C–C–C–H
H H H H
Or CH3CH2CH2CH3
Naming straight-chain Alkanes
• Prefix + ane
• all alkanes have the suffix –ane
• prefix: tells # of C’s
Prefix
Meth
Eth
Prop
But
Pent
Hex
Hept
Oct
Non
Dec
# of C atoms
1
2
3
4
5
6
7
8
9
10
Formula
CH4
C2H6
C3H8
C4H10
C5H12
Name
Meth + ane
Ethane
Propane
Butane
Pentane
Naming Branched-Chain Alkanes
• goal of name is to describe
molecule so you can draw it
Naming branched-chain alkanes
1. Find longest continuous chain of C atoms
- Bends don’t matter!
2. base name derived from # C’s in continuous
chain
9 carbon chain = nonane
3. Branches named first and in alphabetical order
* to name branches, count # C atoms & add “yl”
to prefix name
* If more than one of same type of branch - use di, tri,
etc.
propyl
ethyl
ethyl
methyl
ethyl
triethyl, methyl, propyl
Assign number to Branches based on longest
carbon chain
* you want numbers to add up to the lowest #
propyl
ethyl
ethyl
6
7
8
9
5
4
methyl
ethyl
4, 4, 5, 5, 6 = add up = 24
3
2
1
Assign number to Branches based on longest
carbon chain
* you want numbers to add up to the lowest #
propyl
ethyl
ethyl
4
3
2
1
5
6
methyl
ethyl
4, 5, 5, 6, 6 = add up = 26
7
8
9
4. Put it all together
4,4,6-triethyl 5-methyl 5-propyl nonane
propyl
ethyl
ethyl
1. nonane
2. triethyl, methyl,
propyl
3. 4, 4, 5, 5,
6
7
8
9
5
4
methyl
ethyl
3
2
1