[Costanza9]

Hey guys, I'm kind of confused about this question.I understand how 3 could be correct because you can rotate 1 to get 3. But I'm not sure how to look at these Fischer projections. Thanks for the help.

[Dan]

These are not true Fischer projections as the dashes and wedges are already drawn in - all you need to do is rotate them to get two bonds in the plane of the page.

see http://en.wikipedia.org/wiki/Fischer_projection

[g-bones]

Build models.  Its always a good idea to build a model because then you actually have the 3d structures to compare with each other.  Avoids mistakes by trying to rotate molecules in your mind (even though youll get used to it eventually)

[Costanza9]

I still can't decide which of the choices 4,5,6 is the correct one, how am I suppose to rotate them?

[imanooblar]

Couldn't you find the absolute configuration of 1 (which is S) and find all the other examples that have a configuration of R, which would lead you to the enantiomers?

[Costanza9]

Couldn't you find the absolute configuration of 1 (which is S) and find all the other examples that have a configuration of R, which would lead you to the enantiomers?

Ok I tried doing it this way, I found the configuration of each stereo center. 1 was an S, 2 was an R, 3 was an S, 4 was an S, 5 was an R. (This could be wrong, I am new to this stuff). 3 and 4 were both S, so was the original. The answer is also B (3,4), so would that mean that since the original was S then the same enantiomers would also have to be S?