Which structure represents (S)-1-chloro-1-fluoroethane?
A)I
B)II
C)III
D)More than one of these choices.
E)None of these choices.

Question

Which structure represents (S)-1-chloro-1-fluoroethane? 
A)I 
B)II 
C)III 
D)More than one of these choices. 
E)None of these choices.

Quizplus · Accepted Answer

Both structures I and III represent (S)-1-chloro-1-fluoroethane. This is because the carbon atom bonded to the chlorine, fluorine, and hydrogen atoms has two different groups (chlorine and fluorine) attached, making it a stereocenter. The chlorine and fluorine atoms are arranged opposite each other, which gives the molecule an (S) configuration according to the Cahn-Ingold-Prelog priority rules. Therefore, any structure that correctly shows the arrangement of the chlorine and fluorine atoms in opposite positions around the central carbon atom is a valid representation of (S)-1-chloro-1-fluoroethane.

Which Structure Represents (S)-1-Chloro-1-Fluoroethane