In MarvinSketch, it is possible to draw reactions by placing a reaction arrow on the canvas.
The reaction arrow can be placed in any position, pointing in any direction.
Structures before the arrow are considered reactants, structures along with the arrow agents, and structures after the arrow products.
No Structure labels can be used to annotate unknown structures. These labels can be saved in .mrv, .skc, and .cdx formats. Empty .mol .rxn .rdf files generated after v.15.11.23 are displaying a No Structure label on the canvas when opened.
Only reactions that contain a single reaction arrow can be interpreted chemically and saved in chemical formats.
MarvinSketch allows you to set a map label on any atom in the molecule.
Map labels are useful because they remain constant, unlike atom indexes, which can change as the molecule is altered.
It allows you to specify that specific reactant atoms will become specific product atoms.