Chiral chemicals are a unique class of compounds that are chemically identical but exist as enantiomers (mirror images of each other). These molecules are called chiral or handed, derived from the Greek word cheir, meaning hand. Chiral compounds are very much a part of everyday life. Each form of a chiral molecule can have a profoundly different biological purpose and or effect, even taste or smell. A closer look at the furniture polishes and cleaners under the kitchen sink will reveal much more than meets the eye. Limonene C10H16 is a chemical that is collected from the oil of citrus rind. This molecule is chiral and both enantiomers are commonly found in nature. First the oil is separated from the juice and is then distilled. This process retains the flavor and fragrance of the compound. Limonene is used as a solvent and "wetting agent". It is also used in the manufacture of resins, which are soluble in organic solvents (such as ether) but not in water, flavoring, fragrance and perfume materials. The most common use of this product today is in cleaning products as either a straight solvent or as a product that has been water-diluted. It is when this compound is used as a straight solvent that it is most effective. Chiral compounds like this one interact differently with left and right circular polarized light, depending on their "handedness" Journal of Chem. Ed., 79(5) 572 (2002). This produces circular dichroism (the property of some crystals and solutions of absorbing one of two plane-polarized components of transmitted light more strongly than the other) and birefringence, the refraction of light in an anisotropic (exhibiting properties with different values) material in two slightly different directions to form two rays (Webster 2002). As a result of such interactions the chemical has two different smells and tastes depending on which conformation it is in. The two different enantiomers affect our cells in different ways.
