In the representation of stereochemical relationships 'anti' means 'on opposite sides' of a reference plane, in contrast to '@[email protected]' which means 'on the same side', as in the following examples.
  1. Two substituents attached to atoms joined by a single bond are anti if the @[email protected] (@[email protected]) between the bonds to the substituents is greater than 90°, or @[email protected] if it is less than 90°. (A further distinction is made between @[email protected], @[email protected], @[email protected] and @[email protected])
  2. In the older literature the terms anti and @[email protected] were used to designate @[email protected] of @[email protected] and related compounds. That usage was superseded by the terms '@[email protected]' and 'cis' or E and Z, respectively.
  3. When the terms are used in the context of @[email protected] or @[email protected], they designate the relative orientation of substituents in the substrate or product:
    1. Addition to a carbon-carbon double bond:
    2. Alkene-forming @[email protected]:
      In the examples described under (1) and (2) anti processes are always @[email protected], and @[email protected] processes are @[email protected]
    See also:
    endo, exo, syn, anti
    PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1084 [Terms] [Paper]
    PAC, 1996, 68, 2193. (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2199 [Terms] [Paper]