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Basic Chemistry Copyright © 2011 Pearson Education, Inc.1
Chapter 17 Organic Chemistry
17.1 Alkanes
Compounds in food contain many organic compounds.
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IUPAC Names
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Structural Formulas
Alkanes are written with structural formulas that are• expanded to show each bond• condensed to show each carbon atom and the
attached hydrogen atoms
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Drawing Structural Formulas
Carbon atoms in a chain• maintain their tetrahedral
shape• are connected in a zigzag
pattern• are drawn as two dimensional • can be written in many ways
4
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Some Structural Formulas
5
Rotation of the end CH3-groups provides different representations for butane.
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Learning Check
Draw the condensed structural formula for heptane.
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Solution
Heptane, an alkane, has seven carbon atoms in its carbon chain.
CH3─CH2─CH2─CH2─CH2─CH2─CH3
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Learning Check
Name each of the following:
A. CH3─CH2─CH2─CH3
B. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3
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Solution
A. CH3─CH2─CH2─CH3
four carbon atoms; butane
B. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3
eight carbon atoms; octane
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Isomers of Butane
Isomers• have the same
molecular formula• have different atomic
arrangements• for butane are a
straight chain and a branched chain
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Naming Alkanes with Substituents
In the IUPAC system,• a carbon branch is named as an alkyl
group• halogen atoms are named as halo
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Naming Alkanes
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Example of Naming an Alkane
Give the IUPAC name of CH3 CH3
CH3─CH─CH─CH2─CH2─CH3
STEP 1 Write the alkane name of the longest continuous chain of carbon atoms.
hexane STEP 2 Number the carbon atoms starting from the
end nearer a substituent. CH3 CH3
CH3─CH─CH─CH2─CH2─CH3
1 2 3 4 5 6
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Example of Naming an Alkane (continued)
STEP 3 Give the location and name of each substituent as a prefix to the alkane name.
CH3 CH3 methyl groups on carbons 2 and 3
CH3─CH─CH─CH2─CH2─CH3
1 2 3 4 5 6
2,3-dimethylhexane
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Learning Check
Give the IUPAC name of
Cl CH3
CH3─CH2─CH─CH─CH3
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Solution
STEP 1 Write the alkane name of the longest continuous chain of carbon atoms.
pentane
STEP 2 Number the carbon atoms starting from the end nearer a substituent.
Cl CH3
CH3─CH2─CH─CH─CH3
5 4 3 2 1
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Solution (continued)
STEP 3 Give the location and name of each substituent as a prefix to the alkane name.
Cl CH3
CH3─CH2─CH─CH─CH3
5 4 3 2 1
3-chloro-2-methylpentane
chloro on carbon 3 methyl on carbon 2
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Learning Check
Give the IUPAC name for the following:
Cl CH3
| |CH3─CH2─CH─CH2─C─CH2─CH3
|
Cl
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Solution
STEP 1 Write the alkane name of the longest continuous chain of carbon atoms.
heptane
STEP 2 Number the carbon atoms starting from the end nearer a substituent.
Cl CH3
| |CH3─CH2─CH─CH2─C─CH2─CH3
1 2 3 4 5 | 6 7
Cl
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Solution (continued)STEP 3 Give the location and name of each
substituent as a prefix to the alkane name.
Cl CH3
| |CH3─CH2─CH─CH2─C─CH2─CH3
1 2 3 4 5 | 6 7
Cl
3,5-dichloro-5-methylheptane
chloro on carbon 3 methyl and chloro on carbon 5
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Drawing Alkane Formulas
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Learning Check
Draw the condensed structural formula for
2-bromo-4-chlorobutane.
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SolutionSTEP 1 Draw the main chain of carbon atoms. For
butane, there are four carbon atoms in the chain.
C─C─C─C
STEP 2 Number the chain and place the substituents on the carbons indicated by the numbers.
Br C─C─C─C─Cl
1 2 3 4
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Solution (continued) Br
C ─ C ─ C ─ C ─ Cl
1 2 3 4
STEP 3 Add the correct number of hydrogen atoms to give four bonds to each C atom.
Br CH3─CH─CH2─CH2─Cl
Needs 3 H
Needs 1 H
Need 2 H each