Branched Chains And Isomers

Chapter 10 Alkanes and Aromatic Hydrocarbons Branched Alkanes Structural Formulas

Timberlake LecturePLUS 1999

1

Alkyl Groups Branches on carbon chains H H

H

C H H

H

C

C

H

H

CH3

methyl

CH3CH2

ethyl

Timberlake LecturePLUS 1999

2

Branched Alkanes CH3 CH3CHCH3 methyl groups CH3

CH3

CH3CHCH2CHCH3 Timberlake LecturePLUS 1999

3

Naming Branched Alkanes  

CH3 methyl branch CH3CH2CH2CHCH2CH3 6

5

4

3

2

 

1

Timberlake LecturePLUS 1999

Count

4

Naming Branched Alkanes CH3 methyl branch CH3CH2CH2CHCH2CH3 6

5

4

3

2

1

Count

3-Methylhexane on third C

CH3 six carbon chain group Timberlake LecturePLUS 1999

5

Naming Summary 1. Count the C’s in the longest chain 2. Name each attached group 3 Count the longest carbon chain to give the first attached group the smallest number 4. Name and locate each group Timberlake LecturePLUS 1999

6

Learning Check Alk4 A.

CH3

CH3

CH3CHCH2CHCH3 B.

CH3

CH3

CH3CH2CHCH2CCH2CH3 CH3

Timberlake LecturePLUS 1999

7

Solution Alk4 A.

CH3

CH3

CH3CHCH2CHCH3 B.

CH3

2,4-dimethylpentane

CH3

CH3CH2CHCH2CCH2CH3 Timberlake LecturePLUS 1999 8 CH 3,3,5-trimethylheptane 3

Learning Check Alk5 Write a condensed structure for A. 3,4-dimethylheptane

B.

2,2-dimethyloctane

Timberlake LecturePLUS 1999

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Solution Alk5 A. 3,4-dimethylheptane

CH3

CH3CH2CHCHCH2CH2CH3 CH3 •

2,2-dimethyloctane CH3 CH3CCH2CH2CH2CH2CH2CH3 CH3

Timberlake LecturePLUS 1999

10

Learning Check Alk6 Write 3 isomers of C5H12 and name each.

Timberlake LecturePLUS 1999

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Solution Alk6 CH3CH2CH2CH2CH3

pentane

CH3 CH3CHCH2CH3

2-methylbutane

CH3 CH3CCH3

2,2-dimethylpropane Timberlake LecturePLUS 1999

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Isomers Same molecular formula Same number and types of atoms Different arrangement of atoms

Timberlake LecturePLUS 1999

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Examples of Isomers The formula C4H10 has two different structures CH3 CH3CH2CH2CH3 Butane

CH3CHCH3 2-methylpropane

When a CH3 is is used to form a branch, it makes a new isomer of C4H10. Timberlake LecturePLUS 1999

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Learning Check Alk7 Write the structural formulas of 3 isomers that have the formula C5H12. Name each.

Timberlake LecturePLUS 1999

15

Solution Alk7 Write the structural formulas of 3 isomers that have the formula C5H12. Name each. CH3CH2CH2CH2CH3 CH3 CH3CHCH2CH3

pentane CH3 CH3CCH3

CH3 1999 16 2-methylbutaneTimberlake LecturePLUS 2,2-dimethylpropane