Chirality from Chemistry to Art and Nature: personal observations

Abstract

Human kind has been in some way aware of chirality for millennia and also Kant in 1783 provided a short description of chirality watching his hand in the looking glass. This observation was about nearly a century before Pasteur established stereochemistry (chemistry in three dimensions of the space) as a new area of science and Van’t Ho and Le Bel proposed the hypothesis of an asymmetric tetrahedral carbon atom. Not only Nature is chiral but to a great extent it exists as just one enantiomer (a mirror image not superimposable upon the original) and, in any case, can tell the dierence between right-handed and left-handed helical structures or objects. A planar structure, suitably designed, become chiral if a torsion angle exists that turns it in a tridimensional structure. Also, a hidden relationship exists between tetrahedron and helix. Biological systems possess a marked chirality sense and biological activities as smell, taste, anti-inflammatory are often related to stereochemical properties. Many examples of asymmetry and helicity can be observed in the plant world as twining vines, flowers in specific families of subtropical plants and common pine-cones. In the animal world the most studied area is the asymmetry of gastropods and snail shells. Helicity in the horns in girgentean goats and in ammonites is an example of meso structures, namely structures where a half part of it is a not superimposable mirror image of the other half part. In works of art several varieties of helical columns, stairs, tridimensional spiral decorations in ancient churches and cloisters try to connect earth with heaven and add magnificence to a façade or an altar. Here I present personal observations through photographs concerning enantiomers in the natural world, art and craftworks.