HELP!!!! Ochem

[GRAD]

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Help!!! I never learned fischer projections, and I cant figure out this answer, even with the explanation. please help.. check the link out

http://photos.e46fanatics.com/data/500/fisher.JPG

 

[lifeisgood]

Oh man this is SO easy.

When looking at a Fischer projection, remember that the vertical constituents are pointed into the page (away from you) and the the horizontal are pointed out of the page (toward you). From there you just need to turn the molecule in your mind. If you turn the Br slightly in choice D so it aligns in the same plane as F, and then rotate the entire molecule so it is vertical with the F & Br pointing away from you...you will see that the OH closest to the Br ends up on your left and vice versa for the OH closest to the F.

It's a lot easier to explain by showing someone than trying to explain it here.

Also, if you have a molecule set from O Chem it will really help you visualize these problems.

 

[dds2baz]

You can also check this by the determining whether the chiral centers of both are the same. R means that the first through third priority groups (with #4 in back) are clockwise, S means that the first through third priority groups are counterclockwise. To determine the priority, you have to use the Cahn-Engold-Prelog rules.

 

[GRAD]

You can also check this by the determining whether the chiral centers of both are the same. R means that the first through third priority groups (with #4 in back) are clockwise, S means that the first through third priority groups are counterclockwise. To determine the priority, you have to use the Cahn-Engold-Prelog rules.

sorry still totally confused....what?- i know the thing about vertical and horizontal, but the rotating is confusing me, rotate then rotate again--- what?

 

[GRAD]

sorry still totally confused....what?- i know the thing about vertical and horizontal, but the rotating is confusing me, rotate then rotate again--- what?

And i know about priority, i just dont get what i need to do step by step and it pisses me off when i totally dont understand something =)

 

[allstardentist]

just look in ur ochem textbook and read about the configuration. the concept is simple but theres more to it than what people described it here(even tho they are correct explanations).