[lord12]

CH2-CH-CH3              -CH-CH2-CH3   
       |                        |
       CH3                    CH3


Which of these following amino acids have "D,L" isomers? I'm assuming that the problem is referring to optical isomers.

[chiralic]

Hello Lord12:

These structures are not AMINOACID...

Check this link to see AMINOACID NOMENCLATURE:
http://www.chem.qmul.ac.uk/iupac/AminoAcid/

Chiralic

[lord12]

i meant side chains: that amino acids link does not answer my question

[chiralic]

I suggest that you must read again this link because in this site you'll get information and answer to your post.

chiralic

[chiralic]

Also, you must search on google Cahn Ingold Prelog Rules. You will get a lot information about this topic.

For distinguish between a L-amino acid from D-amino acid you'll must apply the CORN Rule

On IUPAC web site you can find several papers related with Amino acid and Optical Isomers

Regards,

Chiralic

[chiralic]

Sorry, I wrote in incorrect form my suggestion to search on google, I wrote Cahn Ingold Prelog rules  instead Fisher Projections Rules

[Yggdrasil]

An asymmetric carbon (which gives rise to optical isomers) will have four distinct substituents on it.  Can you find any asymmetric carbons on either side chain?