# Confusion in IUPAC Nomenclature

I was trying to name the following compound but I got stuck in naming the aldehydic part of the compound.

I looked for the answer and found it as 6-bromo-2-oxocyclohexanecarbeldehyde. I had come to know earlier that carbeldehyde suffix is used when there are more than two aldehydic group in the compound but why carbeldehyde is used here? I am not able to understand this. If someone can explain which rule is used here. I will be very grateful for this.

• The suggested name is "6-bromo-2-oxocyclohexanecarbeldehyde" is wrong. The correct name is 2-bromo-6-oxocyclohexane-1-carbaldehyde. – user7951 Jul 26 '18 at 17:38
• – user7951 Jul 26 '18 at 17:45
• Okay. But why the suffix carbeldehyde is used here? – gks Jul 26 '18 at 17:46
• Can you please explain why hexane is used instead of hexyl? – gks Jul 26 '18 at 17:54

• Why …carbaldehyde?
It's similar to $$\ce{C6H11-COOH}$$ cyclohexanecarboxylic acid (not cyclohexanoic acid). It's the case where the functional group's carbon is not included in the parent structure. (Such case are also nitriles/carbonitriles, $$\ce{R-CN}$$)

• Why not …hexyl… or rather …cyclohexyl… ?
This (wrong name) would be constructed similarly to a different, non-preferred type of nomenclature, a radical name, which names e.g. ethanol as ethyl alcohol.

• There are more than two aldehydic group in the compound.
They are not. Alhedyde group is $${\ce{-CHO}}$$. The other one, $$\ce{>C=O}$$ is an oxo group (ketone). The group for suffix is chosen by the pre-defined priority, $${\ce{-CHO}}$$ > $$\ce{>C=O}$$.

• Why 2-bromo-6-oxo-… and not 6-bromo-2-oxo-… ?
The groups named by prefixes (after highest priority - suffix group is assigned lowest locant possible) are not numbered by their priority, but such that the assigned locant set is lowest possible. If there are more equivalent possibilities, then they are numbered in the alphabetically sorted order (which is used in the name).

Carbaldehyde is not particulary used when there are two aldehydic groups in a molecule. To describe an aldehyde you either use "-al" or "-carbaldehyde". The difference is that when you use "-carbaldehyde" you also count the carbon, meaning that carbaldehyde stands for "CHO" group including the carbon.

(That is why it is 2-oxo.)