1. [obsolete]@A00472@ between a base and the conjugate acid of a different base through a @H02899@ (B' ... HB+ or A'H ... A). The term has its origin in the @C01266@ and is in no way related to @C01267@ of @O04317@ Heteroassociation is a more appropriate term.
    PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1120 [Terms] [Paper]
  2. [obsolete] Some authors refer to @C01267@ containing a heteroatom, e.g. pyridine, as 'heteroconjugated systems'. This usage is discouraged since it inappropriately suggests an analogy to @H02842@, and conflicts with the currently accepted definition of that term.