Chem: Alkanes

1

Methane

2

Ethane

3

Propane

4

Butane

5

Pentane

6

Hexane

7

Heptane

8

Octane

9

Nonane

10

Decane

Name the Alkane (Condensed Formula):

CH₃CH₂CH(CH₃)CH₂CH₃

3-methylpentane

• Chain: 5 carbons in a row (pentane)

• Branch: One -CH₃ (methyl) group C-3 from either end.

Name the Alkane (Condensed Formula):

CH₃C(CH₃)₂CH₂CH(CH₂CH₃)CH₃

2,2,4-trimethylhexane

• Trap Alert: The -CH₂CH₃ written in parentheses near the right end actually extends the longest continuous chain to 6 carbons (hexane), rather than stopping at 5.

• Numbering: Start from the left so the two methyls get C-2 instead of C-5. That puts methyl groups at C-2, C-2, and C-4.

Name the Alkane (Condensed Formula):

(CH₃)₂CHCH(CH₃)CH₂CH₂CH₃

2,3-dimethylheptane

• Chain: Expanding (CH₃)₂CH- gives CH₃CH(CH₃)-, making a 7-carbon longest chain (heptane).

• Branches: Methyl groups are located at C-2 and C-3 when numbered from the left.

Name the Alkane (Skeletal Description):

• A 6-carbon zig-zag chain with a single line pointing up at carbon 2, and a two-carbon bend pointing down at carbon 4.

4-ethyl-2-methylhexane

• Chain: 6 carbons (hexane)

• Branches: A methyl at C-2 and an ethyl at C-4. (Ethyl before Methyl)

Name the Alkane (Skeletal Description):

• A 5-carbon zig-zag chain with two single lines branching off carbon 2, and one single line branching off carbon 4.

2,2,4-trimethylpentane

• Chain: 5 carbons (pentane)

• Branches: Two methyls at C-2 and one methyl at C-4 (numbering from the left gives 2,2,4, which beats 2,4,4 from the right)

Write the condensed formula from the name:

3-ethyl-2,4-dimethylhexane

CH₃CH(CH₃)CH(CH₂CH₃)CH(CH₃)CH₂CH₃

• Breakdown: Start with a 6-carbon backbone (C-C-C-C-C), attach a -CH₃ at C-2, a -CH₂CH₃ at C-3, and another -CH₃ at C-4, then fill in the remaining hydrogens so each carbon has 4 bonds.