orthonym.rules.isotope_licence

Note

Internal API. Names and behaviour may change between releases.

When the default tier may cite a hydrogen nuclide without its count and without a locant.

(the Blue Book,:43720): the descriptor stands “before the part of the compound that is

isotopically substituted”; “When polysubstitution at a single position is possible, the number of atoms substituted is always specified as a right subscript to the atomic symbol(s), even in case of monosubstitution.” (heading Omission of locants,:44178; the rule:44180): “locants are omitted if no locants are necessary in unmodified names”; (:44202): “Locants are not omitted when there is a possibility of isomers”; Letter and/or numeral locants (:44208): “When locants are needed… then all locants must be cited” (:44210). Printed: ‘(2-2H1)acetic acid (PIN)’ and ‘(O-2H)acetic acid (PIN)’ (:43804,:43806), ‘1,1,1-trifluoro(2-2H1)ethane (PIN)’ (:44155, under Numbering in relation to the unmodified compound), ‘ethan(2H)ol (PIN) (as in ethanol)’ (:44184), ‘(1-14C)pentan(3H)oic acid (PIN)’ (:43812), ‘cyclohexane(2H)carboxylic acid (PIN)’ (:43816), ‘(2H3)acetonitrile (PIN) (as in trichloroacetonitrile)’ (:44182).

A descriptor that cites one hydrogen, count-less and locant-free, is the Blue Book spelling in two places.

• A slot of a group that holds one hydrogen: the nuclide stands directly before the suffix or prefix that names the group (‘ethan(2H)ol’, ‘pentan(3H)oic acid’, ‘cyclohexane(2H)carboxylic acid’, ‘methane(2H)sulfonic acid’, ‘2-(2H)hydroxypropanoic acid’). The position is the group, so there is neither a count to show nor an isomer to tell apart.

• A unit that holds exactly one hydrogen whose unmodified name cites no locant (‘trichloro(2H)methane’, ‘(2H)formonitrile’): the nuclide has no other place, and no locant is necessary in the unmodified name. The unit is the whole compound for a descriptor outside enclosing marks and the group between the marks for a descriptor inside them.

Everywhere else the count is shown or a locant is cited. A front descriptor over a compound with several hydrogens shows its count (‘(2H)phosphoric acid’ has three equivalent OH). It also cites a locant when the hydrogens are not all alike (‘(2H)formic acid’ has the isomer ‘(O-2H)formic acid’) or when the unmodified name cites locants (‘1-chloro-1,2,2,2-tetrafluoroethane’: ‘1-chloro-1,2,2,2-tetrafluoro(1-2H)ethane’).

A count-only descriptor over a retained name whose characteristic group is IMPLIED (implied_group_hydrogens).

(:43800) prints ‘(2-2H1)acetic acid (PIN)’ (:43804) next to ‘(O-2H)acetic acid (PIN)’ (:43806), and (:43824) ‘(N-2H1)acetamide (PIN)’ (:43828): the O-H of ‘acetic acid’ and the N-H of ‘acetamide’ are

positions of the unit the front descriptor stands before, because the name has no suffix of its own for them (‘ethan(2H)ol’,:44184, has one). A descriptor that cites only a count, ‘(2H3)acetic acid’, then has the isomer ‘(2-2H1,O-2H)acetic acid’,:44202), so its locants are cited, ‘(2,2,2-2H3)acetic acid’, and with them the locants of the unmodified name,:44180). The retained parents ‘acetic acid’, ‘acetonitrile’ and ‘acetaldehyde’ omit the locants of their substituents,:3031); while the label sits on that parent the omission is withdrawn (retained_c2_unit_carries_isotope, locant_omission.isotope_retained_c2_unit_scope): ‘2-hydroxy(2,2-2H2)acetic acid’.

OPSIN 2.9.0 rejects the count-less spelling, so it is only ever read through its twin (validation.twin_spellings, rule isotope_count_one).:func:twin_licensed keeps that reading from licensing a count-less spelling where the Blue Book shows the count, and:func:needs_locant sends the placement search on to the locanted spellings where it cites a locant. Both apply at the default tier only: a wider tier shows the count and keeps the names it has.

orthonym.rules.isotope_licence.implied_group_hydrogens(mol, scope, carriers, skel, off)

The heteroatoms of the unit named at off of skel whose hydrogen the unit holds without a slot of its own: the O-H of ‘acetic acid’, the N-H of ‘acetamide’ and ‘acetamido’. mol is the unlabelled structure with explicit hydrogens, scope the carbon run of the labelled carriers (isotopes._element_scope).

(the Blue Book) prints ‘(2-2H1)acetic acid (PIN)’ (:43804) and ‘(O-2H)acetic acid (PIN)’

(:43806); (:43824) ‘(N-2H1)acetamide (PIN)’ (:43828): the front descriptor has the O-H and the N-H of the retained name in its scope, so a count-only ‘(2H3)acetic acid’ has an isomer and (:44202, “Locants are not omitted when there is a possibility of isomers”) cites the locants. A suffix written out carries its own slot, ‘ethan(2H)ol’ (:44184), ‘pentan(3H)oic acid’ (:43812), and a prefix is a unit of its own (‘N-(2H3)acetylacetamide’ labels the acetyl,:43730 ‘(2H3)methoxybenzene’; the unit is then the prefix word, _prefix_head): those hydrogens are not in the scope, and neither is a heteroatom group of the labelled carbon itself (a ‘hydroxy’ prefix or an ‘-ol’ suffix on it).

The implied group is the characteristic group of an acid or an amide: a non-ring heteroatom with a hydrogen, single-bonded to a carbon of the scope that bears a double bond to a heteroatom, and named by the unit (the word ‘acid’ for an oxygen, ‘amid-’ or ‘hydrazid-’ for a nitrogen). An acid group stays implied unless the unit spells it with a suffix slot (_GROUP_SLOT, ‘propanoic acid’); the group of a chalcogen heavier than oxygen has the slot of its systematic suffix (‘ethanethioic S-acid’) and is not read.

orthonym.rules.isotope_licence.retained_c2_unit_carries_isotope(mol)

True when a labelled atom sits on a two-carbon chain unit that a retained parent names: ‘acetic acid’ (and ‘acetate’), ‘acetonitrile’, ‘acetaldehyde’,, . The unit is the carbon C-1 of a carboxyl, ester, nitrile or aldehyde group, the acyclic carbon C-2 bonded to it, and the heteroatoms of the group; an atom of it is labelled when it is, or when a hydrogen on it is, the Blue Book: the locants of the parent are cited when the parent holds the label, not when a substituent does). A label in a substituent unit with marks of its own, an amide unit (‘acetamido’) or a ring is not read; this is a structural proxy for the parent the isotope module does not name (a longer chain reads too, and its producers do not use the retained parents), and every emission stays OPSIN-round-trip-gated. A stereogenic C-2 is not read: the producers cite its descriptor bare (‘(R)-chloro(hydroxy)acetic acid’,,:44643) on the locant-free spelling, which does not fit one that cites its locants, so those names keep the omitted form. Gates isotope_retained_c2_unit_scope.

orthonym.rules.isotope_licence.licensed(skel, off, original)

Whether a count-less, locant-free hydrogen nuclide may stand at off of the unmodified name skel of the structure original (see the module text).

orthonym.rules.isotope_licence.needs_locant(original, skel, off)

True at the default tier when the one labelled hydrogen of original is cited without count at off of skel (it sits on a carrier that bears no other hydrogen) and the Blue Book then cites a locant: the hydrogens of its unit are not all alike, so there is a possibility of isomers, or the unmodified name cites locants. A slot of a one-hydrogen group needs none. The placement search then goes on to the locanted spellings.

orthonym.rules.isotope_licence.twin_licensed(candidate, original)

Whether every count-less hydrogen item of the descriptors of candidate stands where the Blue Book cites it so; the isotope oracle reads a candidate through its twin only then.