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Aldehyde Nomenclature:

The aldehyde fucntional group is a -CHO which looks like this:

nald1.gif (1019 bytes)

The carbonyl carbon (the one connected O and H) is always carbon 1, unless there is a carboxylic acid group on the other end. Hence, the numbers aren't mentioned when mentioning aldehydes.

In order to designate a molecule as an aldehyde, you must drop the "ending" (-ane from an alkane) and add "al" (for aldehyde). Name this molecule:

nald2.gif (1187 bytes)

That would be butanal. Now, try this one:

nald3.gif (1209 bytes)

This would be 3-butenal. Try this one:

nald4.gif (1492 bytes)

2-ethylhex3-ene-4-yne-al. That was a toughie.

When the aldehyde isn't the highest priority group, the prefix formyl- is used. Let's try this one:

nald6.gif (1269 bytes)

This would be formylpentanoic acid. No need to number, because both the carboxylic and aldehyde functional groups are located at the end, and there are ony two ends :)

Cyclic Aldehydes

For cyclic aldehydes, the suffix -carbaldehyde is added to the ring name. Let's check an example:

nald5.gif (1136 bytes)

Cyclopentanecarbaldehyde. Easy, isn't it? Remember that whatever carbon the -CHO group is on, that is carbon-1.


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