How can I draw the structures of the two enantiomers of alanine?

1 Answer
Dec 27, 2014

Draw them as Fischer projections.


The easiest way is to draw them as Fischer projections.

The general formula for an amino acid is RCH(NH₂)COOH.

In alanine, R = CH₃.

You draw the Fischer projection for an amino acid in the same way as for a carbohydrate.

The main chain is vertical, with C-1 at the top. If the NH₂ group is on the left, you have an L-amino acid. If the NH₂ group is on the right, you have an R-amino acid.

So the two structures of alanine are

Note that L-alanine has the (#S#) configuration. If you have to, you can now draw their wedge-dash structures.