I came up with two possible names: benzoyl chloride and benzene carbonyl chloride. I believe both names are correct.

Wikipedia says that the preferred IUPAC name is benzoyl chloride:

Can someone verify it?

  • 2
    $\begingroup$ Please note that chemical names should generally not be capitalised, unless occurring at the beginning of a sentence / in a title. There's no need to capitalise the 'b' in 'benzoyl chloride': in fact, it's wrong to capitalise it. $\endgroup$ Jan 2, 2022 at 11:56
  • $\begingroup$ @orthocresol noted. $\endgroup$
    – DatBoi
    Jan 2, 2022 at 12:24
  • $\begingroup$ @orthocresol maybe capitalize them in a language where nouns generally are capitalized, like "Deutsch". $\endgroup$ Jan 2, 2022 at 15:49
  • $\begingroup$ @OscarLanzi Justifying improper chemical names using fitting rules from an arbitrary language is a great idea. From now on, I'm going to name my benzoyl chloride half-Russian, half-Japanese with a colon in between and peppered with leetspeak: б3н30ил:塩化. Isn't it beautifully useful? $\endgroup$
    – andselisk
    Jan 2, 2022 at 18:16
  • $\begingroup$ Just don't assume the rules of English are universal. $\endgroup$ Jan 2, 2022 at 19:18

1 Answer 1


The relevant rule for the numbering in the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) reads as follows.

P-65.5.1 Acyl halides from suffix acids
P- Acid halides in which hydroxy groups of all acid groups expressed as the suffix denoting the principal characteristic group (carboxylic, sulfonic, sulfinic, selenonic, etc. acids) have been replaced by halogen atoms ($\ce{F}$, $\ce{Cl}$, $\ce{Br}$, and $\ce{I}$) are named by citing the name of the acyl group (see P-65.1.7) followed by the name(s) of the specific class(es) as a separate word(s), in alphabetical order, each preceded by a multiplicative prefix, as needed.
The names formyl, acetyl, benzoyl, oxalyl, and oxamoyl are retained as preferred prefixes.

So yes, the name benzoyl chloride is the preferred IUPAC name.

The suggested name "benzene carbonyl chloride" is not in accordance with IUPAC nomenclature. The similar name benzenecarbonyl chloride is a correct systematic name. However, it is not the preferred IUPAC name since "benzoyl" is the preferred prefix.

Also note that the retained name benzoic acid is the preferred IUPAC name, although the systematic name is benzenecarboxylic acid.


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