[Paul2lyfe]

I have been wondering and searching.I checked Morrison and Boyd for the difference between Mesomerism and Resonance,but I only get the difference between Mesomerism and Resonance Hybrid.I know Mesomerism involves the movement of pie eectrons in an unsaturated ring trying to make it aromatic or stable and a Resonance hybrid gived characteristics of two resonating structures.But my question still remains what is the difference between Mesomerism and Resonance??

[yesway]

I think of them as synonymous with the term "Resonance" as being slightly outdated/historical due to the word hinting at a process which is not taking place. In my opinion, there are only mesomeric limit formulae, and a mesomeric hybrid indicated by the double headed arrow. The movement of pi-electrons in this case is only a formality (although an important formality in order to write down mechanisms).

[curiouscat]

Reminded me of the M&B analogy for resonance I loved:

It's like trying to describe a rhinoceros as a cross between a dragon and a unicorn.

[PhDoc]

M&B really does need to catch up to the 21st century. I haven't heard that term used since 1983!

Resonance, there's no substitute.