http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
The organic chemistry itself is there presenting most major mechanisms in a great step by step arrow pushing format that works very well. Key parts of the mechanism are bold while the non-reactive parts are grayed out making it very easy to follow a reaction even if you are dealing with huge biological molecules.