Why is Symmetry Important in Chemistry?

     Asking why symmetry is important to chemistry is analogous to asking why red blood cells are essential to a human being. While many people are unaware of the microscopic cells constantly flowing through their veins and capillaries, people are aware that there life would be incredibly different without these petite cells. This is akin to symmetry and its integral role in chemistry. Symmetry is involved in virtually everything ranging from a substance's boiling point to the types of bonds it contains, but never receives the credit that it deserves. When put into perspective, symmetry is involved in everything and is located everywhere.

     In organic chemistry, symmetry is incredibly important in determining a substance's boiling point. In one article, the author relates each compound to a piece in the game Tetris™. As illustrated below, the molecule which is most symmetric (labelled easy) has the capability to stack and form multiple layers, leaving few, if any, space between each layer. The piece labelled "hard", on the other hand, is able to stack with itself; however, there will be large gaps left between each layer which will result in a lower melting point than its symmetric counterpart.

     The following two diagrams further emphasize how important symmetry is when stacking molecules. Perfectly symmetric molecules can also be described as Legos™ because they fit perfectly together when stacked.

     Simply put, less gaps will occur when a symmetric molecule is stacked with itself, hence, resulting in a greater melting point.

     Another area of chemistry where symmetry comes into play is in hydrogen bonding. One specific type of hydrogen bond is named the symmetrical hydrogen bond. Just as its name implies, this variety of hydrogen bond is unique because the hydrogen atom is equidistant from two interchangeable atoms, illustrated in the diagram to the left. In the prior paragraph, it was stated that symmetry increases the intermolecular forces between molecules, and similarly, the symmetric hydrogen bonds are much stronger than a regular hydrogen bond. The strength of a symmetric hydrogen bond is comparable to that of a covalent bond. This could mean that a symmetric hydrogen bond has the potential to have almost forty times the bond energy of that of a regular hydrogen bond!

Bonds displayed in hexabenzocoronene

     Another element of symmetry that was stated previously is its role in determining differences in bonds. In an experiment conducted by Leo Gross of IBM research in Switzerland, he discovered that the bonds in a buckyball, made of 60 carbon atoms, had different strengths. Achieved for the first time in 2009, Gross used a technique that was capable of measuring individual bonds. The bonds appeared in different colors which assisted Gross and his colleagues in determining the strengths of the bond, but symmetry also came into play. The symmetry of the atom allowed the researchers to differentiate the background effects which may have been produced by the new imaging technique from the actual bonds themselves. This is seen with the image on the right (http://www.newscientist.com/article/dn22269-first-images-of-chemical-bond-differences-captured.html) . With out the scientists familiarity with the compound symmetric structure, this experiment would have been a waste!

Vitruvian Man

     Symmetry has been valued by humans ever since Leonardo da Vinci created the Vitruvian Man in 1487, a drawing that focuses on the proportions and symmetrical nature of human beings. However currently, there are many other implications of symmetry. Defined by dictionary.com as "the correspondence in size, form, and arrangement of parts on opposite sides of a plane, line, or point; regularity of form or arrangement in terms of like, reciprocal, or corresponding parts", this word has a plethora of value which its definition does not imply. Symmetry is key in determining a compounds boiling point and melting point. Scientists are attempting to create drugs with symmetrical properties in order to cure disease. Symmetry is also giving scientists a better understanding of cancer and it provides incite onto how stem cells function. Symmetry may just be another word, but it is found everywhere and its value in chemistry, and life, is indescribable.