Where to put the number in organic nomenclature? Should one write 4-hydroxypentan-2-one or 4-hydroxy-2-pentanone?
It has been seen that both have been used frequently.
The IUPAC recommendations on this matter have been changed.

According to the 1979 recommendations, the correct name was still 4-hydroxy-2-pentanone.

According to the 1993 recommendations, however, locants were placed immediately before the part of the name to which they relate. This rule is still included in the 2013 version. Therefore, the correct name is now 4-hydroxypentan-2-one.