Is chlorophenylmethane the correct IUPAC name rather than chloromethylbenzene? 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?
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:


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


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

References


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.