In the present context of intermediate and final products, the term "intermediate" is intended to mean intermediate or starting products. Such products are made available with a view to obtaining end products through a physical or chemical change in which the intermediate product loses its identity.
The requirement for the same or corresponding special technical features (Rule 44(1)) is considered to be met in the context of intermediate and final products where:
An essential structural element is a chemical structure that defines the technical contribution that the claimed inventions, considered as a whole, make over the prior art.
Unity of invention may also be present between intermediate and final products of which the structures are not known – for example, as between an intermediate having a known structure and a final product with unknown structure or as between an intermediate of unknown structure and a final product of unknown structure. In such cases, there should be sufficient evidence to lead one to conclude that the intermediate and final products are technically closely inter-related as, for example, when the intermediate contains the same essential element as the final product or incorporates an essential element into the final product.
Different intermediate products used in different processes for the preparation of the final product may be claimed provided that they have the same essential structural element. The intermediate and final products should not be separated, in the process leading from one to the other, by an intermediate which is not new. Where different intermediates for different structural parts of the final product are claimed, unity should not be regarded as being present between the intermediates. If the intermediate and final products are families of compounds, each intermediate compound should correspond to a compound claimed in the family of the final products. However, some of the final products may have no corresponding compound in the family of the intermediate products, so the two families need not be absolutely congruent.
The mere fact that, besides the ability to be used to produce final products, the intermediates also exhibit other possible effects or activities should not prejudice unity of invention.