The molecule (3R,4S)-3-Bromo-4-chlorocyclohexanone is shown below: Which of the following structures depicts the same molecule?

Question

The molecule (3R,4S)-3-Bromo-4-chlorocyclohexanone is shown below:  Which of the following structures depicts the same molecule?

Quizplus · Accepted Answer

11ecba2d_1279_3302_a3bf_31e443848f3b_MD0008_00 A molecule can be depicted in multiple projections and orientations. For each depiction to be equivalent, all atoms within the molecule must be in the same position relative to all other atoms. The question shows the wedge-dash projection of (3R,4S)-3-Bromo-4-chlorocyclohexanone oriented with the ketone on the left. Bromine is bonded to the carbon that is two away from the ketone carbon in the counterclockwise direction, and chlorine is three carbons away. Both bromine and chlorine are bonded to carbon by a dashed line, indicating that they are below or behind the plane of the ring. These features must be preserved in all depictions of the molecule. The answer choices depict the molecule as "chair" conformations, which are commonly adopted by 6-membered rings. Instead of using dashes and wedges, chair projections show substituents in either axial or equatorial positions. Axial positions are perpendicular to the plane of the ring and occupy positions above or below the plane in an alternating pattern; equatorial positions alternate between slightly above and slightly below the plane. Either position (axial or equatorial) can be a dash or wedge, depending on its orientation relative to the plane of the ring. In (3R,4S)-3-Bromo-4-chlorocyclohexanone, both bromine and chlorine are below the plane, and bromine must be two carbons away from the ketone in the counterclockwise direction. Only Choice B satisfies all these requirements. (Choice A) This structure depicts bromine two carbons away from the ketone in the clockwise direction, making it the enantiomer (mirror image) of (3R,4S)-3-Bromo-4-chlorocyclohexanone. (Choice C) This structure reverses the positions of chlorine and bromine so that chlorine is two carbons away from the ketone in the counterclockwise direction. (Choice D) This structure has bromine and chlorine attached to the correct carbons but has bromine in the "up" position instead of the "down" position relative to hydrogen. Educational objective: A molecule can be drawn in multiple ways, with different projections and orientations. For different depictions of the same molecule to be equivalent, the atoms must be drawn in the same position relative to each other.

The Molecule (3R,4S)-3-Bromo-4-Chlorocyclohexanone Is Shown Below: Which of the Following