Reactions:

• Reactions are made up of one or more molecules, as SMILES. Any valid molecule may be a component in a reaction.

• Reactions represent "single-step" entities. A scheme is our construct for multi-step reactions.

• The SMILES language is extended to handle reactions.

New operator for SMILES. The '>' separates the molecules into groups, based on their role in the reaction (eg. reactant, agent, or product).

All parts are optional. ('>>' is a valid reaction)

Each component in a reaction has a role:

Reactant - starting material(s).

Agent - molecule which do not contribute or accept atoms to the overall reaction (catalyst, solvent, etc.)

Product - final result(s).