in chemical nomenclature, a preferred iupac name (pin) is a unique name, assigned to a chemical substance and preferred among the possible names generated by iupac nomenclature. the "preferred iupac nomenclature" provides a set of rules for choosing between multiple possibilities in situations where it is important to decide on a unique name. it is intended for use in legal and regulatory situations.
preferred iupac names are applicable only for organic compounds, to which the iupac has the definition as compounds which contain at least a single carbon atom but no alkali, alkaline earth or transition metals and can be named by the nomenclature of organic compounds. (see below). rules for the remaining organic and inorganic compounds are still under development.
the concept of pins is defined in the introductory chapter (freely accessible) and chapter 5 of the "nomenclature of organic chemistry: iupac recommendations and preferred names 2013", which replace two former publications: the "nomenclature of organic chemistry", 1979 (the blue book) and "a guide to iupac nomenclature of organic compounds, recommendations 1993". the full draft version of the pin recommendations ("preferred names in the nomenclature of organic compounds", draft of 7 october 2004) is also available.