Basic Organic Nomenclature

Halo-alkanes

There are a number of chemical groups which are generally treated as substituents even though they have a higher priority than simple alkanes. Thus, they appear as prefixes to the parent alkane. The rules for naming alkanes which you already know apply to these compounds with the addition of the following prefixes. Even though they have a higher priority than simple alkyl substituents, they have no priority in numbering the parent carbon chain, again simply look for the first point of difference in the chain.
 
 

The structural formula and names for the simple substituents are shown in the following table.

Functional Group
Prefix Name
Example
Line Drawing
3D Model
F
fluoro-
fluoromethane
Cl
chloro-
2-chloropropane
Br
bromo-
2-bromobutane
I
iodo-
iodopropane
NO2
nitro-
nitroethane

There is an additional way that very simple halogen substituted alkanes are named, as the alkyl halide. This only applies to very simple hydrocarbons where the alkyl group can be named as a simple substituent. Examples of this would include (from above): methyl fluoride, isopropyl chloride, sec-butyl bromide, and propyl iodide. Generally once there is more than the single halogen atom on the alkane chain, the halogen becomes a substituent.

The nitro group is always named as a nitro- group (i.e. a substituent).

Tutorial Test 2

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