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Clar's rule states that for a benzenoid polycyclic aromatic hydrocarbon (i.e. one with only hexagonal rings), the resonance structure with the largest number of disjoint aromatic π-sextets is the most important to characterize its chemical and physical properties.
According to Clar's rule, [20] the resonance structure of a PAH that has the largest number of disjoint aromatic pi sextets—i.e. benzene-like moieties—is the most important for the characterization of the properties of that PAH. [21] Benzene-substructure resonance analysis for Clar's rule
One traditional explanation is given by Clar's rule. QTAIM shows that a calculated stabilization of 8 kcal/mol (33 kJ/mol) for phenanthrene is the result of destabilization of the compound by 8 kcal/mol (33 kJ/mol) originating from electron transfer from carbon to hydrogen, offset by 12.1 kcal (51 kJ/mol) of stabilization due to a H...H bond path.
For the second generation reaction starting with the diazoketone, the reaction is performed by irradiation of a 0.7 M solution of the ketone with 1.0-1.2 equivalents of acetylene. A low-pressure mercury-vapor lamp at 254 nm in a photochemical reactor is used for 5–8 hours until all the diazoketone has been consumed as determined by TLC analysis.
The Yukawa–Tsuno equation, first developed in 1959, [1] is a linear free-energy relationship in physical organic chemistry.It is a modified version of the Hammett equation that accounts for enhanced resonance effects in electrophilic reactions of para- and meta-substituted organic compounds.
Erich Clar (23 August 1902 – 27 March 1987) was an Austrian organic chemist, born in Hřensko, who studied polycyclic aromatic hydrocarbon chemistry. He is considered as the father of that field. [ 1 ]
The Nazarov cyclization reaction is a named electrocyclic reaction converting divinylketones to cyclopentenones.. A classic example is the thermal ring-opening reaction of 3,4-dimethylcyclobutene.
Based on Woodward–Hoffmann rules, the electrocyclic opening of norcaradiene derivatives is a 6-electron disrotatory (π 4 s + σ 2 s), thermally allowed process. ring opening. The norcaradiene-cycloheptatriene equilibrium has been studied extensively. [11] The position of the equilibrium depends upon steric, electronic and conformational ...