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Many aromatic and antiaromatic compounds (benzene and cyclobutadiene) are too small to have protons inside of the ring, where shielding and deshielding effects can be more diagnostically useful in determining if a compound is aromatic, antiaromatic, or nonaromatic. Nucleus Independent Chemical Shift (NICS) analysis is a method of computing the ...
They found that closed-shell compounds were aromatic when they had 2(n + 1) 2 π-electrons, for instance the buckminsterfullerene species C 60 10+. [ 15 ] [ 16 ] In 2011, Jordi Poater and Miquel Solà expanded the rule to open-shell spherical compounds, finding they were aromatic when they had 2 n 2 + 2 n + 1 π- electrons , with spin S = (n ...
Aromatization is a chemical reaction in which an aromatic system is formed from a single nonaromatic precursor. Typically aromatization is achieved by dehydrogenation of existing cyclic compounds, illustrated by the conversion of cyclohexane into benzene. Aromatization includes the formation of heterocyclic systems. [1]
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.
In contrast, the corresponding [12]-and [16]annulenes, which are weakly antiaromatic or nonaromatic, have downfield shifted interior hydrogens. However, unlike the undoubtedly aromatic [18]annulene , [14]annulene does not bear the hallmark aromatic property of chemical stability, and it quickly decomposes when exposed to light and air.
Aliphatic compounds can be saturated, joined by single bonds , or unsaturated, with double bonds or triple bonds . If other elements ( heteroatoms ) are bound to the carbon chain , the most common being oxygen , nitrogen , sulfur , and chlorine , it is no longer a hydrocarbon, and therefore no longer an aliphatic compound.
Aromaticity can be induced in compounds having a [10]annulene-type core if planarity is forcibly imposed by other substituents. Two methods to do so are known. One method is to formally replace two hydrogen atoms by a methylene bridge ( −CH 2 − ); this gives the planar bicyclic 1,6-methano[10]annulene ( 5 ).
Heteroarenes are aromatic compounds, where at least one methine or vinylene (-C= or -CH=CH-) group is replaced by a heteroatom: oxygen, nitrogen, or sulfur. [3] Examples of non-benzene compounds with aromatic properties are furan, a heterocyclic compound with a five-membered ring that includes a single oxygen atom, and pyridine, a heterocyclic compound with a six-membered ring containing one ...