Editing Mesomeric effect (section)

== Mesomerism in conjugated systems ==
Mesomeric effect can be transmitted along any number of carbon atoms in a [[conjugated system]]. This accounts for the resonance stabilization of the molecule due to delocalization of charge.<ref name=":4">{{Citation |last=Balci |first=Metin |title=12 - Chemical Shift |date=2005-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780444518118500127 |work=Basic 1H- and 13C-NMR Spectroscopy |pages=283–292 |editor-last=Balci |editor-first=Metin |place=Amsterdam |publisher=Elsevier Science |language=en |doi=10.1016/b978-044451811-8.50012-7 |isbn=978-0-444-51811-8 |access-date=2022-10-25}}</ref>  It is important to note that the energy of the actual structure of the molecule, i.e. the resonance hybrid, may be lower than that of any of the contributing canonical structures. The difference in energy between the actual inductive structure and the (most stable contributing structures) worst kinetic structure is called the resonance energy or resonance stabilization energy.<ref name=":5">{{Cite book |title=Elsevier Enhanced Reader | chapter=Chapter 2-2 - Theory of the Chemical Shift |url=https://reader.elsevier.com/reader/sd/pii/B9780080229539500119?token=5A916B90719B3D354C0B813BC4EFBA7F642C6C025D8A2D5F023C5074CCA975BAE0F8DBB064700B375C959401D6EFC297&originRegion=us-east-1&originCreation=20221025163518 |access-date=2022-10-25 |website=reader.elsevier.com | series=International Series in Organic Chemistry | date=January 1969 | pages=61–113 | publisher=Pergamon | doi=10.1016/B978-0-08-022953-9.50011-9 | isbn=9780080229539 |language=en}}</ref> For the quantitative estimation of the mesomeric/resonance effect strength various substituent constants are used, i.e. Swain-Lupton resonance constant, Taft resonance constant or Oziminski and Dobrowolski [[Pi electron donor-acceptor|pEDA]] parameter.

Additionally, the resulting resonance structures can give the molecule properties that are not inherently evident from looking at one structure. Some of these properties include different reactivities, local [[Diamagnetism|diamagnetic]] shielding in aromatics, deshielding, and acid and base strengths.<ref name=":6">{{Cite journal |last1=Peter |first1=K. |last2=Vollhardt |first2=C. |date=January 1978 |title=A Review of: "The Place of Transition Metals in Organic Synthesis. Ed. D. W. Slocum. Annals of The New York Academy of Sciences, Volume 295, New York, N.Y., 1977, XXIV + 282 pp. $3 2.00" |url=http://dx.doi.org/10.1080/00945717808057443 |journal=Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry |volume=8 |issue=5–6 |pages=505–506 |doi=10.1080/00945717808057443 |issn=0094-5714}}</ref>