I thought that the correct IUPAC name for the molecule below (benzyl chloride) would be chloromethylbenzene because the ring always gets priority over the chain unless a primary functional group is present. However, it seems the correct name is chlorophenylmethane. Can someone explain why that is?

chloromethylbenzene or chlorophenylmethane?


The preferred IUPAC name is, indeed, (chloromethyl)benzene, built from substitutive prefix chloromethyl. The parentheses around "chloromethyl" are required because it is a compound substituent (a simple substituent attached to another simple substituent, specifically, methyl and chloro in this case). The Blue Book [1, p. 66] has plenty of examples similar to yours:

$$ \begin{array}{lll} \ce{C6H5-CH2-NCS} &\quad &\text{benzyl isothiocyanate} \\ & &\text{(isothiocyanatomethyl)benzene (PIN)} \\ & & \\ \ce{C6H5-NC} &\quad &\text{phenyl isocyanide} \\ & &\text{isocyanobenzene (PIN)} \end{array} $$

Note that common names for this molecule also include: benzyl chloride and α-chlorotoluene.


  1. Favre, H. A.; Powell, W. H. IUPAC “Blue Book” Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names; IUPAC Recommendations; Royal Society of Chemistry: Cambridge, England, 2013. ISBN 978-0-85404-182-4.
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    $\begingroup$ The remark about the use of parentheses is correct. However, the actual question was whether the preferred name is chloro(phenyl)methane or (chloromethyl)benzene. $\endgroup$ – user7951 Jun 29 '19 at 12:00
  • $\begingroup$ @Loong You are right. I was (and still am) too lazy to look up the relevant rules so just decided to edit in a brief line about the parentheses; I leave it to you if you want to expand further or write another answer. $\endgroup$ – orthocresol Jun 29 '19 at 13:02
  • $\begingroup$ Is 1-phenyl methyl chloride possible? $\endgroup$ – Chakravarthy Kalyan Jun 30 '19 at 2:43

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