Naming Aldehydes IUPAC:Replace -e with -al. The aldehyde carbon is number 1. If -CHO is attached to a ring,use the suffix-carbaldehyde. => Chapter 18 6 Chapter 18 6 Naming Aldehydes • IUPAC: Replace -e with -al. • The aldehyde carbon is number 1. • If -CHO is attached to a ring, use the suffix -carbaldehyde. =>