IUPAC nomenclature of Organic compound - Alkane family

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ALKANES

They are hydrocarbons without double or triple bond functional groups, depending on whether the carbon atoms of the molecule are arranged only in chains or also in rings. Although these hydrocarbons have no functional groups, they constitute the frame work on which functional groups are located in other classes of compounds, and provide an idea starting point for studying and naming organic compounds. The alkanes are also members of a larger class of compounds referred to as aliphatic. Alkanes posses the general formula C_nH_2n+2.

The table below lists the IUPAC names assigned to simple continuous chain alkanes from C–1 to C–10.

Number of Carbon    Names            Structure

1                      Methane           CH₄

2                      Ethane              C₂H₆

3                      Propane           C₃H₈

4                      Butane             C₄H₁₀

5                      Pentane           C₅H₁₂

6                      Hexane            C₆H₁₄

7                      Heptane           C₇H₁₆

8                      Octane             C₈H₁₈

9                      Nonane           C₉H₂₀

10                    Decane           C₁₀H₂₂

Examples of structures of Alkanes.

Methane (CH₄)                        

 

Butane (C₄H₁₀)

                                   

IUPAC Rules for Alkane Nomenclature

1.   Find and name the longest continuous carbon chain.

2.   Identify and name the groups attached to this chain.

3.   Number the chain consecutively, starting at the end nearest a substituent group.

4.   Designate the location of each substituent group by appropriate number and name.

5.   Assemble the name, listing groups in alphabetical order.

      Note: The prefixes di, tri, tetra etc. (i.e. two, three four respectively) used to designate several groups of the same kind are not considered when alphabetizing.

6.   Separate numbers from alphabet using hyphen(-) and also separate numbers from numbers using comma (,).

Example 1

Name this compound

Solution

According to the rule stated above.

1.   The longest carbon chain is Butane (C–4)

2.   The group attached to this group is methyl (CH₃)

3.   The substituent (methyl) is on Carbon 2

Note: you start numbering the carbon from where the substituent is close to.

 

In accordance with the information stated above the name of the structure is  2 – Methylbutane

Example 2

 Give a name to this compound. CH₃CHClCH₂CHICH(C₂H₅)CH₂CHFCH₂Br

Solution

According to the rules for alkanes nomenclature.

1.   The longest carbon chain is octane (C–8)

2.   The groups attached to this chain are, alkyl and halogens.

3.   The numbering must be started from the right hand side to the left hand side because the substituent is closer to the right end.

4.   The substituent is as follows alphabetically: 1-Bromo, 7-Chloro, 4-Ethyl, 2-Floro, 5-Iodo.

In accordance with the information stated above the name of the structure is 1-Bromo-7-Chloro-4-Ethyl-2-Floro-5-Iodooctane .............. for further questions contact the blogger