orthonym.perception.lambda_hydride

Note

Internal API. Names and behaviour may change between releases.

λ-hydride heteroatom perception — IUPAC /.

A neutral skeletal atom whose bonding number exceeds its standard value (Table 1.3) carries the λ-convention, e.g. a tetrahydridophosphorus substituent -PH4 is λ5-phosphanyl. This module answers the narrow perception question the substituent namer needs: “is this phosphorus a λ5 hydride (-PH4)?”, as opposed to a phosphoryl / phosphonic P=O (also bonding number 5, but named by the oxoacid subsystem —.

The distinction is load-bearing (the collision): both have bonding number 5, so the λ-hydride detector fires ONLY when every non-attachment bond of the phosphorus is to hydrogen. Fail-closed: a charged P, a radical, a ring P, or any O/N/S neighbour / multiple bond declines.

References

IUPAC 2013 Blue Book, / (bonding number, Table 1.3) IUPAC 2013 Blue Book, (λ-convention on neutral atoms) IUPAC 2013 Blue Book, (λ5-phosphanyl substituent)

orthonym.perception.lambda_hydride.is_lambda_hydride_phosphorus(mol, atom_idx)

True iff atom_idx is a λ5-hydride phosphorus (-PH4 / PH5).

Requires: symbol P; neutral; no radical; NOT in a ring; nonstandard bonding number of exactly 5; and every non-attachment bond to hydrogen — i.e. at most one heavy-atom neighbour (the parent attachment) and all bonds single. This EXCLUDES a phosphoryl / phosphonic P=O (multiple heavy neighbours and a P=O double bond), which the oxoacid subsystem names.