Chemical substance In organic chemistry, there can be more than one chemical compound with the same composition and molecular weight. Generally, these are called isomers. Isomers usually have substantially different chemical properties, and often may be isolated without spontaneously interconverting. A common example is glucose vs. fructose. The former is an aldehyde, the latter is a ketone. Their interconversion requires either enzymatic or acid-base catalysis. However, tautomers are an exception: the isomerization occurs spontaneously in ordinary conditions, such that a pure substance cannot be isolated into its tautomers, even if these can be identified spectroscopically or even isolated in special conditions. A
Chemical nomenclature of technical terms used in chemistry. Similar compendia exist for biochemistry (the "White Book", in association with the IUBMB), analytical chemistry (the "Orange Book"), macromolecular chemistry (the "Purple Book") and clinical chemistry (the "Silver Book"). These "color books" are supplemented by shorter recommendations for specific circumstances that are published periodically in the journal "Pure and Applied Chemistry". The primary function of chemical nomenclature is to ensure that a spoken or written chemical name leaves no ambiguity concerning which chemical compound the name refers to: each chemical name should refer to a single substance. A less important aim is to ensure