304.2 - An aldehyde group in a cyclic compound is named by the prefix "formyl-" when a group having priority for citation as principal group is also present.
Examples to Rule C-304.1
304.3 - A -CHO group attached to a nitrogen atom in a ring system is denoted by the prefix "formyl-" (see Rule C-824.2) or according to Rule C-304.1.
Example to Rule C-304.2
304.4 - When the aldehyde group is separated from the ring by a chain of carbon atoms, the compound is named (a) as a derivative of the acyclic system or (b) by conjunctive nomenclature.
Example to Rule C-304.3
304.5 - When a compound RCH3 has a trivial name, the related aldehyde RCHO may be named as the product of its substitution by O= the prefix "oxo-" is used to denote this substitution (see Rules C-411.1, and C-415.1).
Examples to Rule C-304.4
See Recommendations'93 R-5.6.1
Example to Rule C-304.5
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