Naming alkenes advanced with priority functional groups
Names of organic compounds have three parts: prefix(es) stem ending
The ending is -ene if a compound containing a double bond has no other oxygen-containing functional groups.
The stem depends on the number of carbons in the longest chain containing the double bond and any functional groups that are higher priority than a double bond (that is, any oxygen-containing or nitrogen-containing functional groups).
If a double bond is present, a number preceeds the en.
Prefixes are used to indicate the type and position of any substituents on the longest chain.
Any atom or group of atoms replacing H at a carbon is called a substituent.
meth - 1 carbon
eth - 2 carbons
prop - 3 carbons
but - 4 carbons
pent - 5 carbons
hex - 6 carbons
3-methylpent-2-ene
eth - 2 carbons
prop - 3 carbons
but - 4 carbons
pent - 5 carbons
hex - 6 carbons
3-methylpent-2-ene
The ending is -ene if a compound containing a double bond has no other oxygen-containing functional groups.
If the compound also contains an OH group, the ending is -ol.
If the compound also contains an aldehyde functional group (-CHO), the ending is -al.
If the compound contains a carboxylic acid group (-CO2H), the ending is -oic acid.
If the compound also contains an aldehyde functional group (-CHO), the ending is -al.
If the compound contains a carboxylic acid group (-CO2H), the ending is -oic acid.
The stem depends on the number of carbons in the longest chain containing the double bond and any functional groups that are higher priority than a double bond (that is, any oxygen-containing or nitrogen-containing functional groups).
In the alkene above, the longest chain containing the double bond has five carbon atoms.
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The stem also has -an- or -en- to indicate the presence or absence of unsaturation in the longest chain.If you have trouble seeing this move your mouse over the image.
If a double bond is present, a number preceeds the en.
Example: CH3CH2CH2CH=CHCH2OH is hex-2-en-1-ol.
Prefixes are used to indicate the type and position of any substituents on the longest chain.
Any atom or group of atoms replacing H at a carbon is called a substituent.
CH3–
CH3CH2–
CH3CH2–
methyl
ethyl
ethyl
Br–
Cl–
Cl–
bromo
chloro
chloro
Note that saturated hydrocarbon substituents have the same name as the parent alkane except with ane substituted by -yl
The number of the carbon bearing the functional group that appears in the ending determines the numbering of the chain. See the unsaturated alcohol example above.In a haloalkane, the halogen substituent has the lowest possible number.
For alkanes, the alkyl substituent has the lowest possible number.
For alkanes, the alkyl substituent has the lowest possible number.