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#14 polycyclic compounds
Currently we have
CHEBI:33635 polycyclic compounds
CHEBI:33636 bicyclic compounds
CHEBI:33640 cage compounds
CHEBI:35293 fused compounds
CHEBI:33671 heteropolycyclic compounds
CHEBI:35295 homopolycyclic compounds
CHEBI:33599 spiro compounds
CHEBI:35990 bridged compounds
where
I cannot find a good definition of bridged compound so
I put in CHEBI:35990 "Polycyclic compounds in which two
rings have two or more atoms in common."
based on Gold Book definition of bridge "A valence bond
or an atom or an unbranched chain of atoms connecting
two different parts of a molecule."
I feel this is a bit broad definition; for instance,
can biphenyl be called bridged as well?
If we restrict bridged compounds to the definition in
CHEBI:35990, does it mean we have to make
fused compounds is_a bridged compounds ?
Fused compounds is a special case of bridged compounds
where bridge is "a valence bond".
Shall we create "ring assemblies" class for biphenyls,
stilbenes etc?
Kirill
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Your definition of bridged compounds suffers in that it is
really a definition either of a compound that has a single
bridge or of what comprises a 'bridged system' (this need
only be part of a complete compound). Compounds with
multiple bridges can also be classed as bridged compounds
but these aren't catered for within the definition as it
stands. It is very difficult to come up with a valid
definition of a 'bridged compound' which presumably is why
we haven't come across one yet! Possibly we need to state
first that a bridged compound is a compound that contains
one or more bridge systems and then define 'bridge system'.
Fused compounds must technically all also be bridged
compounds but would not normally be regarded as such and I
think it would not be useful to the users of the ontology
to see them classified as such.
Biphenyl does not have a bridge across two different parts
of a molecule. It is a ring assembly. We do need to create
a 'ring assemblies' class to include biphenyls - but not
stilbenes. IUPAC defines ring assemblies as "two or more
cyclic systems....that are joined to each other BY SINGLE
OR DOUBLE BONDS..." (my emphasis). Such a definition
discounts stilbenes, in which the cyclic systems are joined
by a divalent substituent.