chirality

Chirality is that property of molecules related to non-superimposability of arrangements of attached groups -- stereoisomers. For amino acids, the CORN law determines naming. CORN is an acronym for the -COOH (caboxylic acid group), the -R group (indicating the side chain) and -NH2 (the amine group).

Moving from the alpha-carbon to the carboxylic acid group, then the -R group, then the -NH2 group spells the acronym CORN. If CORN fits a clockwise arrangement, then the molecule is the L- form, where the amino group is on the L-eft side in its Fisher projection of the compound. This is the form found in all biologically generated amino acids. Conversely, an anti-clockwise CORN arrangement is the D-form. More modern notation refers to R- and S- stereo-isomers or enantiomers.

As depicted below, the molecule can be imagined with the H superimposed on the thumb, and the CORN groups in the palm of the left or right hand.

Stereochemistry