orthonym.rules.ketenes

Note

Internal API. Names and behaviour may change between releases.

Ketene namer.

Ketene is the class name for H2C=C=O and its derivatives. The unsubstituted structure and its halogen derivatives are named on the ethenone parent (BB verbatim examples):

C=C=O -> ethenone (PIN)
BrC(Br)=C=O -> dibromoethenone (PIN; "not dibromoketene")

SCOPE (fail-closed, accuracy-first): the exact terminal heterocumulene O=C=C< where the sp carbon carries NOTHING else and the terminal carbon carries only hydrogen and/or halogens. Halogens are the “compulsory prefix” substituents the retained class name allows, and the single substitutable carbon makes the prefix locants unambiguous (BB cites dibromoethenone with no locants). Everything else fails a guard and cascades onward — alkyl/aryl ketenes (2-butylhex-1-en-1-one) and ylidene ketenes (cyclohexylidenemethanone) are named by the general ketone principles, which are NOT built here; never a wrong name.

Graph/atom classifier (no SMARTS broadening); pure — no mol mutation.

orthonym.rules.ketenes.name_ketene(mol)

Return the ethenone-parent PIN for a (halo)ketene, else None.