Chemical patents

• Chemical patents are patent claims which include a structural component. This commonly takes the form of a Markush structure, which is a combination of diagrams and text which describe the set of molecules being claimed. Most modern Markush structures include one or more generic groups such as "any alkyl group", "any ring system" or "a blocking group", so the claim is actually for an infinity of molecular structures (albeit a small infinity).

• The two most awkward things about chemical patents are that: (1) they are legal documents and are interpreted in the "opinion of the court", and (2) they are often used to obscure information rather than elucidate it. The result is that structural claims tend to describe legal positions rather than describing nature (in contrast to most scientific information).

• Even so, an enormous amount of valuable information appears in patents which is published nowhere else.

• The two most important chemical patent searching systems today are those offered by CAS and Derwent. These are both commercial systems which require unique, mutually incompatible queries and are not yet available as generic WWW network services.

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