Relating structure with Fischer projection

[MTD52]

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Okay so there really is no way to present this online the way it is on the test, since they are pictures of structures, but I'm gonna attempt the question anyway. If anyone has the 2008-2009 Kaplan blue book and did this, it's #71 and I would love the help 🙂

Anyway, it asks which of the structures matches its Fischer projection shown. The molecule has only 2 carbons, both are chiral - one with D, OH, and Br attached and the other with H, OH, and F attached.

The groups are shown as a dotted line (going in), a solid "wedge" line (coming out), or just a straight line (don't know if that means in or out?). I have no idea how to distinguish which groups would face in/out and how they correspond to a Fischer projection.

I know it's a tough question to be answered without visualizing, but I really appreciate the help

 

[loveoforganic]

Sure-fire way to do it would be to assign stereochemistry in the Fischer projection, then look for the saw-horse structure with the same stereochem

 

[MTD52]

I thought of that, but I don't know how to do it when it's not Fischer or Newmann because I don't know if that straight line bond means coming out or going in.

 

[loveoforganic]

Could you be a little more explicit? I'm not sure what the problem is.

 

[MTD52]

Could you be a little more explicit? I'm not sure what the problem is.

Sure, I'll try. I tried to explain it in the first post. Actually, here I drew it in paint to make it easier. There should be a link at the bottom. Terrible drawing I know, but essentially those are the way the bonds are drawn in the structure. As far as I know, in order to determine the R/S you need to know which bonds are coming in and going out so you can draw the right Fischer projection to relate it to.

I know the dotted line means going in and the black wedge means going out. I just don't know if the straight line (red arrow points at it) means in or out.

 

[loveoforganic]

It means "in the plane of the page"

 

[MTD52]

It means "in the plane of the page"

Ok, so how does that translate into Fischer? It's only in (vertical) or out (horizontal) when you draw that.

 

[loveoforganic]

I'm having a hard time finding a way to explain it. See if this link helps.

http://neon.otago.ac.nz/chemlect/chem191/stereochemistry/fischer%20projections/fischer.htm

 

[TooQuickSlick]

You have to rotate the saw horse to match the fischer projection