orthonym.rules.ring_ylidene_prefix#

Note

Internal API. Names and behaviour may change between releases.

‘-ylidene’ prefix of an UNSATURATED monocyclic ring fragment: ‘cyclohex-2-en-1-ylidene’, ‘cyclohexa-2,4-dien-1-ylidene’, ‘2H-pyrrol-2-ylidene’, ‘4H-thiopyran-4-ylidene’.

gives a substituent group joined to its parent by a double bond the ending ‘ylidene’ in

place of ‘yl’, on the same parent hydride, the Blue Book, “All mancude rings and ring systems are named by method (2) in “). The saturated carbocycle (‘cyclohexylidene’) is built by substituent_enumerator._carbon_ylidene_prefix; the unsaturated ring had no producer, so the gate of carbon_free_valence_prefix refused it (‘-yl’ would describe a different molecule) and a molecule whose senior ring carries such a prefix had no default-tier name.

  • Carbocycle: the free valence takes locant 1 (the lowest,, the ring is numbered for the lowest ‘ene’ locants: the token of the ‘-yl’ producer (ring_substituents._unsaturated_carbocyclic_substituent) with its ending exchanged.

  • One-heteroatom ring: the ylidene atom is the INDICATED-HYDROGEN position of the mancude parent, ‘4H-thiopyran-4-ylidene (PIN)’, the Blue Book); the numbering, the ‘hydro’ prefixes and the indicated hydrogen are those of the ‘-yl’ producer (ring_substituents._unsaturated_heteromonocyclic_substituent(..., ylidene=True)). A ylidene atom that is a hydro position instead needs the added-hydrogen form, ‘naphthalen-1(2H)-ylidene’), which is not built: the producer declines.

Only a bare ring is named here (the fragment IS the ring: a decorated ring is named by the decorated ring producers), and only a plain neutral ring with no isotope, no CIP label and no stereo double bond. carbon_free_valence_prefix re-reads the token’s own text (two free valences) before it is used, so a token that spelled one would never ship.

orthonym.rules.ring_ylidene_prefix.unsaturated_monocycle_ylidene_prefix(mol, frag_atoms, attach_idx, free_valence)#

The ylidene prefix of the unsaturated monocycle frag_atoms, or None (decline).