The resonance hybrid structure of the benzene molecule causes it to:

●         Have electrostatic potential,

●         Be very stable, and

●         Insert itself into human DNA

Taken together, these molecular and electrical characteristics of benzene make it harmful to humans. 

This summary provides a brief background of each of these characteristics; however, cross-disciplinary discourse and research aimed at understanding benzene’s effect on living organisms is desperately needed to more clearly understand how this unique molecule wreaks havoc on the human body. 

Benzene is a resonance hybrid

The six carbons and six hydrogens of benzene are joined into a hexagonal ring with alternating single and double bonds. As explained very well by Dr. Edwin Thall, benzene can be viewed as a hybrid of III and IV and represented by V.

The resonance hybrid structure of benzene is shown as a hexagonal ring with a circle drawn inside to indicate that the single and double bonds are constantly alternating.

Benzene displays characteristics of its contributing structures depicted by III and IV, but is not actually either of these structures.  For an analogy, consider crossing a bloodhound with a greyhound: The puppy inherits the strong smell and speed characteristics of its parents, but it does not flip flop between a bloodhound one instant and a greyhound the next. The puppy is a hybrid of its parents. Likewise, benzene “inherits” the bonds that characterize structures III and IV, but displays a unique hybrid of these contributing structures.  

For more information about benzene's resonance hybrid structure, please refer to the detailed article, Resonance Hybrid, written by Mr. Parkinson.

Benzene’s electrostatic potential

Benzene’s resonance hybrid structure causes its six electrons to be shared equally by the six carbons. This is depicted as a cloud of negative electron density above and below the carbons.

These electron bonds of benzene (referred to as Pi electrons) produce a large electromagnetic flux field (in medicine, this is known as electrostatic potential). When the Pi electrons travel from atom to atom around the benzene ring, they create an electromagnetic flux field, as illustrated in this graphic by Kenneth Eward at http://www.biografx.com/catalog/slides/kmq460.jpg. Although there is currently a lot of controversy about if and to what extent electromagnetism affects human health, little doubt remains that magnetic fields cause breaks in human DNA, which leads to DNA damage, leukemia, and cell death.

Benzene’s stability

Resonance means movement of electrons over a number of bonds. Electrons are delocalized and shared by several atoms, which results in stabilization of the electrons and lower reactivity.

The resonance hybrid structure and electrostatic potential of benzene make it very stable and reduces benzene’s reactivity in chemical reactions. Thus, when benzene enters the body through our skin or by inhalation, it likely travels unimpeded by the immune system.

Benzene inserts itself into human DNA

Its hexagonal shape allows benzene to fit between base pairs in DNA to cause genetic mutations. Short-term health risks attributed to benzene exposure include temporary nervous system disorders, immune system depression, and anemia. Long-term risks include chromosome damage and forms of cancer that include leukemia. 

According to Dr. Mae-Wan Ho at the Institute of Science in Society, scientists need to talk to each other and collaborate across the disciplines to get at the explanation of how molecules like benzene affect the human body.