Friday, October 28, 2011

Naming of Hydrocarbons - No.1 Site For Learning Chemistry (10th Carbon and Its Compounds)

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IUPAC Rules for Naming Hydrocarbons

1.Choose the correct ending: - ane, - ene, or - yne

2.Determine the longest carbon chain. Where a double or triple bond is present, choose the longest chain that includes this bond. If there is a cyclic structure present, the longest chain starts and stops within the cyclic structure.

3.Assign numbers to each C of the parent chain. For alkenes and alkynes the first carbon of the multiple bond should have the smallest number. For alkanes the first branch (or first point of difference) should have the lowest . Carbons in a multiple bond must be numbered consecutively.

4 .Attach a prefix that corresponds to the number of carbons in the parent chain. Add cyclo- to the prefix if it is a cyclic structure.

5.Determine the correct name for each branch (“alkyl” groups include methyl, ethyl, propyl, etc.)

6.Attach the name of the branches alphabetically, along with their carbon position, to the front of the parent chain name. Separate numbers from letters with hyphens (e.g. 4-ethyl-2-methyldecane)

7.When two or more branches are identical, use prefixes (di-, tri-, etc.) (e.g. 2,4-dimethylhexane). Numbers are separated with commas. Prefixes are ignored when determining alphabetical order. (e.g. 2,3,5-trimethyl-

8.When identical groups are on the same carbon, repeat the number of this carbon in the name. (e.g. 2,2-dimethylhexane)

Naming Side Chains

Example: use the rules to name the following structure

Rule 1: choose the correct ending

Rule 5: Determine name for side chains               1-hexene

Rule 6: attach name of branches alphabetically    2-ethyl-4-methyl-4-methyl-1-hexene

Rule 7: group similar branches                             2-ethyl-4,4-dimethyl-1-hexene


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