Alkanes and Aromatic Hydrocarbons Branched Alkanes Structural Formulas

Alkyl Groups Branches on carbon chains H H C CH 3 methyl H H H H C C CH 3 CH 2 ethyl H H

Branched Alkanes CH 3 CH 3 CHCH 3 methyl groups CH 3 CH 3 CH 3 CHCH 2 CHCH 3

Naming Branched Alkanes CH 3 methyl branch CH 3 CH 2 CH 2 CHCH 2 CH Count

Naming Branched Alkanes CH 3 methyl branch CH 3 CH 2 CH 2 CHCH 2 CH Count 3-Methylhexane on third C CH 3 six carbon chain group

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

Learning Check A. CH 3 CH 3 CH 3 CHCH 2 CHCH 3 B. CH 3 CH 3 CH 3 CH 2 CHCH 2 CCH 2 CH 3 CH 3

Solution A. CH 3 CH 3 CH 3 CHCH 2 CHCH 3 2,4-dimethylpentane B. CH 3 CH 3 CH 3 CH 2 CHCH 2 CCH 2 CH 3 CH 3 3,3,5-trimethylheptane

Learning Check Write a condensed structure for A. 3,4-dimethylheptane B. 2,2-dimethyloctane

Solution A. 3,4-dimethylheptane CH 3 CH 3 CH 2 CHCHCH 2 CH 2 CH 3 CH 3 B.2,2-dimethyloctane CH 3 CH 3 CCH 2 CH 2 CH 2 CH 2 CH 2 CH 3 CH 3

Learning Check Write 3 isomers of C 5 H 12 and name each.

Solution CH 3 CH 2 CH 2 CH 2 CH 3 pentane CH 3 CH 3 CHCH 2 CH 3 2-methylbutane CH 3 CH 3 CCH 3 2,2-dimethylpropane CH 3

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

Examples of Isomers The formula C 4 H 10 has two different structures CH 3 CH 3 CH 2 CH 2 CH 3 CH 3 CHCH 3 Butane 2-methylpropane When a CH 3 is is used to form a branch, it makes a new isomer of C 4 H 10.

Learning Check Write the structural formulas of 3 isomers that have the formula C 5 H 12. Name each.

Solution Write the structural formulas of 3 isomers that have the formula C 5 H 12. Name each. CH 3 CH 2 CH 2 CH 2 CH 3 pentane CH 3 CH 3 CH 3 CHCH 2 CH 3 CH 3 CCH 3 CH 3 2-methylbutane 2,2-dimethylpropane