There are some molecules that are almost identical, only they are mirror-images of each other. These molecules are called chiral, from the Greek word for ‘hand,’ as hands also come in identical mirror-image pairs. Some of the molecules are even distinguished with the prefixes R- and S-. The R is short for Rectus, Latin for right. The L is from the Latin word Sinister, meaning left. So, in a sense, there are ‘right-handed’ and ‘left-handed’ molecules.
These Right/Left differences can be surprising. Carvone is found in two common herbs, but one form gives its taste to Spearmint, the other to Caraway Seeds. In the 1950’s, Thalidomide was prescribed to many mothers. What they didn’t know was that while the right-handed isomer of Thalidomide was a harmless treatment for morning sickness, the left-handed isomer caused horrible birth defects.