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IUPAC Atropisomers is defined as following

A subclass of conformers which can be isolated as separate chemical species and which arise from restricted rotation about a single bond, e.g. ortho-substituted biphenyl, 1,1,2,2-tetra-tert-butylethane.

The word atropisomer is derived from the Greek a, meaning not, and tropos, meaning turn. The name was coined by Kuhn in 1933, but atropisomerism was first detected in 6,6’-dinitro-2,2’-diphenic acid by Cristie in 1922.


  1. PAC, 1996, 68, 2193 (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2200
  5. Wiki Article
  6. axial chirality


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