Which of the following structures has the R configuration?

Question

Quizplus · Accepted Answer

According to the Cahn-Ingold-Prelog priority rules, in compound I, the methyl group is priority group 1, the ethyl group is priority group 2, and the hydrogen is priority group 3. In order for the molecule to have a R configuration, the lowest priority group (in this case, hydrogen) must be pointing away from the viewer. In compound II, the priority groups are arranged such that the hydrogen is pointing away from the viewer, indicating an R configuration. In compound III, the priority groups are arranged such that the hydrogen is pointing towards the viewer, indicating an S configuration. Therefore, the correct answer is B) Only II.

Which of the Following Structures Has the R Configuration