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It was introduced in 1972 by the Austrian organic chemist Erich Clar in his book The Aromatic Sextet. The rule states that given a polycyclic aromatic hydrocarbon , the resonance structure most important to characterize its properties is that with the largest number of aromatic π-sextets i.e. benzene-like moieties .
The first, which was proposed by Kekulé in 1865, later proved to be closest to the true structure of benzene. This structure inspired several others to draw structures that were consistent with benzene's empirical formula; for example, Ladenburg proposed prismane, Dewar proposed Dewar benzene, and Koerner and Claus proposed Claus' benzene ...
All carbon–carbon bonds in benzene are chemically equivalent. In MO theory this is a direct consequence of the fact that the three molecular π orbitals combine and evenly spread the extra six electrons over six carbon atoms. Structure of benzene. In molecules such as methane, CH
Diagram showing the ortho, meta and para positions relative to a substituent X on a benzene ring. Electron donating groups are typically divided into three levels of activating ability (The "extreme" category can be seen as "strong".)
In molecules which have resonance or nonclassical bonding, bond order may not be an integer.In benzene, the delocalized molecular orbitals contain 6 pi electrons over six carbons, essentially yielding half a pi bond together with the sigma bond for each pair of carbon atoms, giving a calculated bond order of 1.5 (one and a half bond).
Two different resonance forms of benzene (top) combine to produce an average structure (bottom). In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected by the stabilization of conjugation alone.
SOURCE: Integrated Postsecondary Education Data System, Virginia Commonwealth University (2014, 2013, 2012, 2011, 2010).Read our methodology here.. HuffPost and The Chronicle examined 201 public D-I schools from 2010-2014.
It is sometimes erroneously called "benzene hexachloride" (BHC). They have been used as models for analyzing the effects of different geometric positions of the large atoms with dipolar bonds on the stability of the cyclohexane conformation. [1] The isomers are poisonous, pesticidal, and persistent organic pollutants, to varying degrees.