What does the suffix "-al" signify in IUPAC naming?

The suffix "-al" in IUPAC naming signifies the presence of an aldehyde functional group. Aldehydes are characterized by the presence of a carbonyl group (C=O) attached to the terminal carbon of a carbon chain, which is what distinguishes them from other functional groups like ketones, alcohols, and ethers.

In the context of organic nomenclature, the use of the suffix "-al" indicates that the compound being named has an aldehyde, and it also implies that the aldehyde carbon is numbered as the first carbon in the structure. As a result, when naming compounds with the aldehyde functional group, "-al" is used as a terminal suffix to denote this specific functional characteristic.

This understanding is essential for accurately identifying and categorizing organic molecules according to their functional groups and for proper IUPAC naming conventions.