Heterocyclic Systems

Rule B-5. Radicals

5.11 - Univalent radicals derived from heterocyclic compounds by removal of hydrogen from a ring are in principle named by adding "yl" to the names of the parent compounds (with elision of final "e", if present).

Examples to Rule B-5.11

Indolyl from indole
Pyrrolinyl from pyrroline
Triazolyl from triazole
Triazinyl from triazine
(For further examples see Rule B-2.11.)

The following exceptions are retained: furyl, pyridyl, piperidyl, quinolyl, isoquinolyl and thienyl (from thiophene) (see also Rule B-2.12). Also retained are furfuryl (for 2-furylmethyl), furfurylidene (for 2-furylmethylene), furfurylidyne (for 2-furylmethylidyne), thenyl (for thienylmethyl), thenylidene (for thienylmethylene) and thenylidyne (for thienylmethylidyne).

As exceptions, the names "piperidino" and "morpholino" are preferred to "1-piperidyl" and "4-morpholinyl".

5.12 - Bivalent radicals derived from univalent heterocyclic radicals whose names end in "-yl" by removal of one hydrogen atom from the atom with the free valence are named by adding "-idene" to the name of the corresponding univalent radical.

Example to Rule B-5.12



or 1,4-Dihydro-4-pyridylidene

5.13 - Multivalent radicals derived from heterocyclic compounds by removal of two or more hydrogen atoms from different atoms in the ring are named by adding "-diyl", "-triyl", etc., to the name of the ring system.

Example to Rule B-5.13


5.21 - The use of "a" terms (Rule B-4) does not affect the formation of radical names. Such names are strictly analogous to those of the hydrocarbon analogous except that the "a" terms establish enumeration in whole or in part.

Examples to Rule B-5.21



See Recommendations'93 R-2.5

Cationic Hetero Atoms


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