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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.
Given a list of NBOs for an idealized natural Lewis structure, the NRT functional creates a list of Lewis resonance structures and calculates the resonance weights of each contributing resonance structure. [1] Structural and chemical properties, such as bond order, valency, and bond polarity, may be calculated from resonance weights. [2]
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 ]
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 NFL’s new kickoff rule did what it was implemented to do in the preseason. Nearly 300 kickoffs were returned in the preseason, a 70.5% return rate that was the highest since 2014.
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.