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I don't know why my solutions manual says these are enantiomers:

enter image description here

The Fisher projections I drew suggest that these are identical compounds.

enter image description here

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The solutions manual is correct, they are enantiomers. The compound on the left is (R)-2-chloro-(S)-3-butanol and the compound on the right is (S)-2-chloro-(R)-3-butanol. Try to use the "R\S" nomenclature system on the 2 chiral carbons, that should help figuring out whether they are identical [(R,R and R,R), (S,S and S,S), (R,S and R,S), (S,R and S,R)] enantiomers [(R,R and S,S), (R,S and S,R), (S,R and R,S)] or diastereomers [(R,R and R,S), (R,R and S,R), (S,S and S,R), (S,S and R,S)].

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  • $\begingroup$ Did I draw the Fischer projections wrong? $\endgroup$ – Dissenter Jun 18 '14 at 13:29
  • $\begingroup$ Yes, I believe the chlorine should be on the "inside" and the hydroxyl on the "outside" in the drawing on the left. $\endgroup$ – ron Jun 18 '14 at 13:31
  • $\begingroup$ Hm, that suggests that I was looking at the molecule incorrectly when drawing the Fischer projections. From which perspective should I look at the molecules? $\endgroup$ – Dissenter Jun 18 '14 at 13:34
  • $\begingroup$ For me, it is easier to draw and understand Newman projections rather than Fisher projections. I know Newman projections have been discussed previously in your posts, but have you tried them? $\endgroup$ – ron Jun 18 '14 at 13:39
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    $\begingroup$ In the 3-dimensional views of the question, the 4 carbons are arranged in a trans (anti) conformation. To draw the Fischer projection you should mentally rotate C-C bonds to all be in the cis (syn) conformation. $\endgroup$ – DavePhD Jun 18 '14 at 17:46
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In the following figure, everything on the left is identical and everything on the right is identical.

enter image description here

See this page for how to draw Fischer Projections.

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