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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.
Tropone or 2,4,6-cycloheptatrien-1-one is an organic compound with some importance in organic chemistry as a non-benzenoid aromatic. [2] The compound consists of a ring of seven carbon atoms with three conjugated alkene groups and a ketone group.
If R 1 and R 2 (note equation at top of page) are different substituents, there is a new stereocenter formed at the alpha position when an enol converts to its keto form. Depending on the nature of the three R groups, the resulting products in this situation would be diastereomers or enantiomers .
The mesomeric effect however, deals with restructuring and occurs when the electron pair of the substituents shift around. The inductive effect only acts on alpha carbons, while the mesomeric utilizes pi bonds between atoms. [4] While these two paths often lead to the similar molecules and resonance structures, the mechanism is different.
Such a resonance structure is called a Clar structure. In other words, a polycyclic aromatic hydrocarbon with a given number of π-sextets is more stable than its isomers with fewer π-sextets. [1] [2] In 1984, Glidewell and Lloyd provided an extension of Clar's rule to polycyclic aromatic hydrocarbons containing rings of any size. [3]
Extreme acidity, heat, and dehydrating conditions are usually required. Other hydrocarbon oxonium ions are formed by protonation or alkylation of alcohols or ethers (R−C− + −R 1 R 2). Secondary oxonium ions have the formula R 2 OH +, an example being protonated ethers. Tertiary oxonium ions have the formula R 3 O +, an example being ...
The following is the reaction mechanism of a nucleophilic aromatic substitution of 2,4-dinitrochlorobenzene (1) in a basic solution in water. Nucleophilic aromatic substitution Since the nitro group is an activator toward nucleophilic substitution, and a meta director, it is able to stabilize the additional electron density (via resonance) when ...
Squaric acid, also called quadratic acid because its four carbon atoms approximately form a square, is a diprotic organic acid with the chemical formula C 4 O 2 (OH) 2. [4]The conjugate base of squaric acid is the hydrogensquarate anion HC 4 O − 4; and the conjugate base of the hydrogensquarate anion is the divalent squarate anion C 4 O 2− 4.