How would you draw tryptophan and select the chiral carbon?

1 Answer
Nov 24, 2015

The chiral carbon, if there is one, tends to be the #\mathbfalpha# carbon on an amino acid.

Tryptophan is the only amino acid that has two rings on it. At pH 7.4, it looks like this:

You can see the chiral carbon highlighted. You can tell that it's an #sp^3# carbon and that it has four different substituents on it (#"H"#, #"NH"_3^(+)#, #"COO"^(-)#, and #"CH"_2-"stuff"#). Therefore it's chiral.