MolSynapsequestion bank
MolSynapse / Question bank / Stereoisomerism / Chirality, enantiomers and R/S configuration
JEE Advanced levelSingle correct optionDifficulty 3 of 3st179

A flat drawing of 1-bromo-2-chlorocyclopropane has ring carbons C1 (bearing Br), C2 (bearing Cl) and C3 (CH) running clockwise as seen from above. Both Br and Cl point up (towards the viewer), and the other substituents are H. What is the configuration?

  1. A(1R,2S)
  2. B(1R,2R)
  3. C(1S,2S)
  4. D(1S,2R)

Answer: A

At C1: Br > C2 (Cl,C,H) > C3 (C,H,H) > H, and H points down. Viewed from above Br (outward), C2, C3 run clockwise, so C1 is R. At C2: Cl > C1 (Br,C,H) > C3 (C,H,H) > H, again H down. Viewed from above Cl (outward), C1, C3 run counter-clockwise, so C2 is S. The cis compound is (1R,2S) (confirmed by explicit CIP assignment); the trans compounds are (1R,2R)/(1S,2S).
Practice Stereoisomerism More on Chirality, enantiomers and R/S configuration
Previous questionNext question

More questions on Chirality, enantiomers and R/S configuration