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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.
The effect of the substituent may change the rate-determining step (rds) in the mechanism of the reaction. A certain electronic effect may accelerate a certain step so that it is no longer the rds. [14] [non-primary source needed] [non-primary source needed] change in rate determining step. A change in the mechanism of a reaction also results ...
However, another effect that plays a role is the +M effect which adds electron density back into the benzene ring (thus having the opposite effect of the -I effect but by a different mechanism). This is called the mesomeric effect (hence +M) and the result for fluorine is that the +M effect approximately cancels out the -I effect. The effect of ...
Contributing structures of the carbonate ion. In chemistry, resonance, also called mesomerism, is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or forms, [1] also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory.
Other structural factors that influence the magnitude of the acid dissociation constant include inductive effects, mesomeric effects, and hydrogen bonding. Hammett type equations have frequently been applied to the estimation of pK a. [3] [4] The quantitative behaviour of acids and bases in solution can be understood only if their pK a values ...
Step 1: Protonation of the phenol group Acetic anhydride is a source of acetyl cation (CH 3 CO +). In the presence of a Lewis acid catalyst like sulfuric acid, the acetyl cation can react with the lone pair of electrons on the oxygen atom of the phenol group of p-Chlorocresol to protonate it, forming a resonance-stabilized carbocation intermediate.
In organic chemistry, ether cleavage is an acid catalyzed nucleophilic substitution reaction. Depending on the specific ether, cleavage can follow either S N 1 or S N 2 mechanisms. Distinguishing between both mechanisms requires consideration of inductive and mesomeric effects that could stabilize or destabilize a potential carbocation in the S ...
The first example of an oxidative phenol coupling in synthetic chemistry can be traced to Julius Löwe’s 1868 synthesis of ellagic acid, accomplished by heating gallic acid with arsenic acid. [8] In the synthesis of complex organic compounds, oxidative phenol couplings are sometimes employed.