Delocalization is a very important concept to understand in organic chemistry. Questions regarding delocalization have routinely popped up on the MCAT and are often a "favorite" topic for questions on organic chemistry exams. So what does "delocalized" or "delocalization" really mean anyway?
Delocalization is a very important concept to understand in organic chemistry. Questions regarding delocalization have routinely popped up on the MCAT and are often a “favorite” topic for questions on organic chemistry exams. So what does “delocalized” or “delocalization” really mean anyway?
Delocalization is a term to describe what happens when pi bond electrons are not held in a single orbital, but instead share their time between several. This means that the electrons are flowing around several atoms in the same molecule.
A good and common example is benzene, a molecule made of a 6 carbon ring. In this molecule the 6 electrons that we show as 3 alternating pi bonds are not actually focused on specific atoms. Instead, they are spread over the 6 carbons in the ring.
The idea of delocalization that is most important to remember is that the electrons from the pi bonds (p orbitals) are “delocalized” or spread out over the whole system (group of interacting conjugated atoms). This means they are spread out between the molecule’s atoms, instead of being concentrated only in the pi bonds we draw.
Delocatized electrons are often drawn in older resources as solid line curves or cirlces inside of carbon rings. In newer books they are sometimes depicted as 3D electron cloud type pictures or a dotted line or curved line next to the atoms which share the delocalized electrons.
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