Naming organic compounds

Question

I am having a little trouble naming benzoic aldehyde using IUPAC rules. It should be phenylmethanal according to outside sources, but how do I figure that out? I know that they assumed the benzene ring to be a substituent, thus the phenyl in the name, but is it like a rule that we should value naming the aldehyde as the main group and treat the benzene ring as a substituent? Couldn't it be the other way around? I found an example of a compound named methylbenzene, so here the methyl group is treated as the substituent and not the benzene ring :/

Answer 1

You need to know which functional group has the highest priority. In the case of a benzene ring and aldehyde. The aldehyde has higher priority and is therefore the suffix. Since the benzene is of lower priority, it is the pre-fix. I would search "functional group priority" to find a list or check your textbook.