Naming Alkanes

• Name, draw, and construct structural models of alkanes

Include: branched alkanes, structural isomers

Additional KEY Termsalkyl group substituent

Alkanes· distinguished by C-C single covalent bonds

· general formula Cn H2n+2

· considered saturated (all single bonds)

PropaneC3H8

Methane CH4

C - C - C H

HH

HH

H

H

H

A carbon branch (substituent) off the parent chain is called an Alkyl group.

The alkyl groups follow the same naming system but end in "yl”.

Formula Name

–CH3 methyl

–C2H5 or –CH2CH3 ethyl

–C3H7 or –CH2CH2CH3

propyl

Methyl group attached to a hexane parent chain.

C - C - C - C - C - C

C

1. Find the longest continuous chain of carbons. • This is the parent chain.

Ethyl branch attached to a hexane chain:

C - C - C - C

C

C

C - C -

1

2

3 4 5 6

6

5

4 3 2 1

2. Branches - Number the carbons of the parent chain from the end that gives the lowest number to the first branch:

3. Name each alkyl group including the number of the parent carbon it is attached to showing position.

4. Names are all ONE word. • Hyphens used to separate numbers from words.

3-ethylhexane

C - C - C - C

C

C

C - C -

1

2

3 4 5 6

Draw the structural formula for 2-methylhexane.

1 2 3 4 5 6

CH3CH(CH3)CH2CH(CH3)CH3

2,4-dimethylpentane

1 2 3 4 5

5. Multiple alkyl groups require prefixes (di, tri) and parent numbers for each.

• The alkyls are named in alphabetical order.• Commas are used to separate numbers.

(5-ethyl-2,4-dimethyloctane)

C - C - C - C

C

C

C - C -

6

5

4 3 2 1

C

4-ethyl-2-methylhexane

5-ethyl-2,4-dimethyloctane

C - C - C - C - C - C

C

C

C - C - 3

4

5 6

C

7 81 2

C

3,3,5trimethyloctane

3 4

5

6 7 8

12

3-ethyl-2,7-dimethyl-4-propyloctane

CH3CH2CH2CH(C2H5)CH2C(CH3)2CH3

4-ethyl-2,2-dimethylheptane

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CAN YOU / HAVE YOU?

• Name, draw, and construct structural models of alkanes

Include: branched alkanes, structural isomers

Additional KEY Termsalkyl group substituent