Editing Mesomeric effect (section)

=== +M effect ===
The +M effect, also known as the positive mesomeric effect, occurs when the substituent is an electron donating group. The group must have one of two things: a lone pair of electrons, or a negative charge. In the +M effect, the pi electrons are transferred from the group towards the conjugate system, increasing the density of the system. Due to the increase in [[electron density]], the conjugate system will develop a more negative charge. As a result, the system under the +M effect will be more reactive towards [[electrophiles]], which can take away the negative charge, than a [[nucleophile]].{{Citation needed|date=May 2024}}

[[File:Mesomeric effect (+M) V.1.png|thumb|500px|+M effect from a methoxy ({{chem2|\sOCH3}}) substituent|center]]'''+M effect order:'''<ref name=":0">{{Cite journal |last=Murrell |first=J N |date=1955-11-01 |title=The Electronic Spectrum of Aromatic Molecules VI: The Mesomeric Effect |url=https://iopscience.iop.org/article/10.1088/0370-1298/68/11/303 |journal=Proceedings of the Physical Society. Section A |volume=68 |issue=11 |pages=969–975 |doi=10.1088/0370-1298/68/11/303 |bibcode=1955PPSA...68..969M |issn=0370-1298}}</ref>

:{{chem2|[[Oxide ion|\sO-]] > [[Amine|\sNH2]] > \sNHR > \sNR2 > [[Alcohols|\sOH]] > [[ether|\sOR]] > [[amide|\sNHCOR]] > [[ester|\sOCOR]] > [[Phenyl group|\sPh]] > [[fluorine|\sF]] > [[Chlorine|\sCl]] > [[bromine|\sBr]] > [[iodine|\sI]] > [[Nitroxyl|\sNO]]}}