question of the day 6/5/12

[Barravel]

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I don't mean to infringe on any copyright, but this is the second time that this question has appeared in Kaplan's question a day and I contacted them last time about a possible error and never received a response. I just want to know if I am right or wrong, so here's the question:

What is the most appropriate R/S naming prefix for the compound shown (attached)?
My answer is 2S,3R, but this is not any of the choices. You can find the full question on Kaplan's website:

https://www.freequestionaday.com/play/mcat

Again, it's the question of the day 6/5/12, and even if you see this post in the future, you can look at past questions and find today's question.

Thanks!

 

[rjosh33]

I'm getting 2S, 3R as well. What do they say is the right answer?

 

[Barravel]

Attached is their answer/explanation (they say it is 2R, 3S). In their explanation it appears to me that they have changed the stereochemistry in their figures from the original diagram. In other words, if you look at their two figures in the explanation, they are actually enantiomers 🙂 None of the answer choices give the option that we think is the answer...

 

[Testosterone]

I don't think the left straight chain form stereoisomer matches the Newman projection given. Also I don't think the hydrogen atoms are "trans" to each other since this is a noncyclic pentane. This might need to be confirmed by someone else but I'm pretty sure the label "trans" is reserved for alkenes, alkynes and cyclic compounds.