PP 33: Branched Alkanes
Drill: Give the molecular formula & the condensed, skeletal, complete, & stick structures of an alkane
with the same # of carbons as the # of letters in your first name.
Branched Compounds: Any hydrocarbon chain the has at least one of mid-chain hydrogen’s replaced
with another hydrocarbon group. An example follows:
H H H
H
H C C C H
H
C C
H H H
methylethylpropylbutylpentyl-
6-C
7-C
8-C
9-C
10-C
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hexylheptyloctylnonyldecyl-
Branched Chains:
• When an alkane chain gets another hydrocarbon group substituted onto it
• Branches: alkyl groups or sidechains
Drill: Draw C8H18 using 4 different methods:
C
Methylpropane
Alkyl Groups:
• Any smaller chain of hydrocarbons that is connected to another longer chain
• The hydrocarbon group that replaces the H is called an alkyl group
• Suffix: -yl: hydrocarbon group
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H
H H H
Propane
Alkyl Groups:
1-C
2-C
3-C
4-C
5-C
CH3
H
The following branched alkane chain (drawn by the skeletal method) will be used to demonstrate
how to name branched alkane chains:
C
C C
C C
C
C
C
C
C
C
1. Find the longest continuous carbon chain &
name it as the main chain. The final name
of the alkane will end with the naming of
the main chain
C-C–C–C–C–C
C
C-C
C
2. Number each carbon in the chain;
so that, the side chains will be connected
to the lowest possible numbers on the
carbons
3. Name the side chains or substituted
groups, & precede them with the
number of the carbon they are
connected to & a dash
4. If identical groups appear more
than once, use prefixes: di for 2,
tri for 3, tetra for 4, penta for 5, etc
(Examples: dimethyl, tripropyl, etc)
C1 – C2 – C3 – C4 – C5 – C6
C
C
2-methyl
C1 – C2 – C3 – C4 – C5 – C6
C 2-methyl C – C 4-ethyl
C
2,2 - dimethyl
C1 – C2 – C3 – C4 – C5 – C6
C
5. Name the sidechains or groups in
alphabetical order, but ignore the
prefixes when doing so (Examples:
ethyl comes before dimethyl, e < m)
C-C
C – C 4-ethyl
4 – ethyl – 2, 2 - dimethyl
6. Separate numbers with commas,
use hyphens between words &
4 – ethyl – 2, 2 - dimethylhexane
numbers, and write the alkanes
as one word. (Example: dimethylhexane)
Name each of the compounds drawn on the black board:
Drill: Name the following compound:
CH2 – CH3
•
H3C – CH – CH2 – CH – CH - CH2 – CH3
CH2 – CH3
CH3
Name each of the following compounds:
CH2 – CH2 – CH3
H3C- CH2
C
CH3 – CH – CH – CH2 – CH – CH2 – CH3
C
CH2 – CH2 – CH3
C–C–C
C–C-C
Drill: Name the following compound:
CH3
CH2 – CH3
CH3 – CH – CH2 – CH2 – CH – CH3
CH2 – CH3
Deriving Organic Structures from Organic Names:
•
•
Draw the main chain first
– Look to the name ending
Draw the branches
– Look to the # & group name
Demonstration: 3,4 – diethyl – 2 – methyloctane
1) Draw the main chain 1st : (octane):
2) Draw the branches:
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
Draw the Following:
•
•
4,5-diethyl-3,4,5-trimethyloctane
3,3,4,4,5,5-hexaethylheptane
Isomers: Compounds that have the same chemical formula, but different shapes
• Isomers will also have a different name
Types of Isomers:
• Structural or skeletal: When there are differences in the carbon skeleton
•
Examples
C–C–C–C–C
• Geometric or cis/trans
pentane
• Functional
• Positional
• Optical
All the other types of isomers will be discussed later
C–C–C–C
C
C–C–C
C
C
2 – methylbutane 2,2-dimethylpropane
Draw & name all the possible structural isomers for C6H14:
Draw & name all the possible structural isomers for C7H16:
Draw & name all the possible structural isomers for C8H18:
Drill: Draw & name 5 possible structural isomers for C7H16 :
Name or draw each of the following:
•
•
•
3,5-diethyl-3,5-dimethyloctane
3,5-diethyl-2,4,6-trimethyloctane
5-butyl-3-ethyl-2,6,6,8-tetramethyl-4-propylnonane
Draw the condensed, complete, skeletal, & stick structures for: 3-ethyl-2,2-dimethylpentane
Draw & name all the possible structural isomers for C9H20:
Drill: Name & describe 5 organic prefixes & 4 organic suffixes:
Test Review:
Be able to identify:
• Organic terms
• Organic prefixes
• Organic suffixes
Be able to name organic compounds:
Be able to draw the structure of organic compounds from the names:
Be able to draw & name isomers when given an organic formula:
Name each of the following:
Draw the various structures of:
• 3 - ethyl - 2- methylpentane
• 3 – ethyl - 2,4,5-trimethylhexane
• Octamethylhexane
• 5 - buty l- 3 - ethyl - 2,4,6,8 – tetramethyl – 4 - propyldecane
• Draw & Name 10 isomers of: C8H18