Help! KBB practice exam fischer projection question

[diene]

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This is #71 from the practice exam on the back of KBB.
How is my projection wrong? I really don't understand how kaplan's answer makes sense. What am i missing here?

 

[aminsarraf]

This is how you should view it. There are 2 chiral carbons in this compound. You must only view one of the chiral carbons and put its groups next to it and see where the other substituent of the second chiral group lies down. (Ultimately, to make it easy on yourself, dont think of the dash and wedge lines)

Look at the chiral carbon with F from the FRONT VIEW. Then this shows you that two OH group are on the same side. D and H are on the same side.

Hope this helps!

 

[diene]

But that doesn't always work, does it? In the same problem, in some choices the 2nd carbon has Br that is dashed and I would to rotate that and take into account dashes/wedges

 

[aminsarraf]

I dont know about the other types of questions unless I see it. My best advice is to look at it as the Newman projection and look at one chiral carbon from the Frontal view. its like the TFE section of PAT.

 

[diene]

Thanks for your help! I will def use this!

Does anyone have any other tricks that work all the time?

 

[SN1]

Thanks for your help! I will def use this!

Does anyone have any other tricks that work all the time?

I believe there is a method that will work 100% of the time. That is to assign R&S. It is gonna take time to do them but realize that most of the answer choices are similar so you are only going to have to do them once or twice and with practice you'll do them quickly.

 

[diene]

Haha that's what I did initially but that did not work out too well. I guess I will practice that