In all sections of the IPC, in the absence of an indication to the contrary, the Periodic System of chemical elements referred to is the one with eight groups as represented in the table below. For example, group C07F 3/00 “Compounds containing elements of Groups 2 or 12 of the Periodic System” refers to the elements of columns IIa and IIb.

Chemical Compounds

When the subject of the invention concerns a chemical compound per se (organic, inorganic or macromolecular), it is classified in section C according to its chemical structure. When it also concerns a specific field of use, it is also classified in the place provided for that field of use, if such field of use constitutes an essential technical characteristic of the subject.

However, when the chemical compound is known and the subject of the invention concerns only the application of the compound, it is classified in the place covering the field of use as invention information while the chemical structure may also be classified in the place for the chemical compound per se as additional information.

Chemical Mixtures or Compositions

When the subject of the invention concerns a chemical mixture or composition per se, it is classified in a place according to its chemical composition if such a place exists, for example, C03C (glass), C04B (cements, ceramics), C08L (compositions of organic macromolecular compounds), C22C (alloys). If such a place does not exist, it is classified according to its use or application.

If the use or application also constitutes an essential technical characteristic of the subject of the invention, a mixture or composition is classified according to both its chemical composition and its use or application. However, when the chemical mixture or composition is known and the subject of the invention concerns only its use, it is classified in the place covering the field of use as invention information while the mixture or composition may also be classified in the place for the chemical mixture or composition per se as additional information.

Preparation or Treatment of Compounds

When the subject of the invention concerns a process of preparation or treatment of a chemical compound, it is classified in the place for the process of preparation or treatment of the compound concerned. If such a place does not exist, it is classified in the place of the compound. When the compound resulting from the preparation process is also novel, the compound is also classified according to its chemical structure. Subjects of invention concerned with general processes for the preparation or treatment of classes of compounds are classified in the groups for the processes employed, when such groups exist.

General Chemical Formulae

Large sets of related chemical compounds are often expressed or claimed using general formulae. The general formulae are presented in the form of a chemical compound genus with at least one component of the formula being a variable selected from a specific collection of alternatives (for example, “Markush”-type compound claims). The use of general formulae causes classification problems when an enormous number of compounds are within their scope and are separately classifiable in a large number of classification places. When this situation occurs, only the individual chemical compounds most useful for searches are classified. If chemical compounds are specified using a general chemical formula, the following classifying procedure is applied:

Step 1: Classification should be given to all “fully identified” compounds that are novel and non-obvious if they are:

i. specifically claimed as such or in a composition,

ii. products of a claimed process, or

iii. derivatives of either of these.

A compound is considered to be “fully identified” where:

a) the structure is given by an exact chemical name or formula, or can be deduced from its preparation from specified reactants, not more than one of which is selected from a list of alternatives, and

b) the compound is characterised by a physical property (for example, its melting point), or its preparation is described in a worked example giving practical details.

Compounds identified only by an empirical formula are not considered to be “fully identified”.

Step 2: If no “fully identified” compounds are disclosed, e.g. in the situation of compounds derived from computer-generated models and which have not undergone actual experiments, classification should only be given to compounds with an exact chemical name or a developed chemical formula. Classification should be limited to a single or a very small number of groups.

Step 3: When only the general Markush formula is disclosed, classification is made in the most specific group(s) that cover(s) all or most of the potential embodiments. Classification should be limited to a single or a very small number of groups.

Step 4: In addition to the above obligatory classification, non-obligatory classification may be made when other compounds within the scope of the general formula, or compounds derived directly from computer-generated models, are of interest.

When classification of all the “fully identified” compounds into their most specific classification places would lead to a high number of classification symbols (for example, more than twenty), the classifier may reduce the number of symbols. This may only be done when classification of the “fully identified” compounds would lead to the assigning of a large number of subgroups under a single group at the next hierarchically higher level. Classification of these compounds may then be made in the higher group only. Otherwise, classification of the compounds is made in all of the more specific subgroups.