Quantum mechanics explains why Möbius ring molecules are different
Rings of carbon with an iconic twist in their structures break the rules for building strongly stable molecules, and now a mathematical proof explains why.
Strongly stable molecules are useful because they hold together long enough to be used in plastics, pipes and polyester clothing. One class of molecules that holds together especially well is called aromatic (though not all of them have odors).
Ring-shaped molecules like benzene, which is the essential precursor in many drugs and plastics, are called aromatic when a particular orbital shell is filled by six electrons, 10 electrons, 14 electrons and so forth — as long as the number of electrons is two plus a multiple of four.
In 1964, Swiss-German chemist Edgar Heilbronner suggested that putting a twist in the ring would change the rules — a Möbius molecule would be aromatic if it contained any multiple of four electrons.