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Likewise a 4-hydroxyl pyrylium compound is a γ-pyrone or pyran-4-one (4), to which group belong compounds such as maltol. pyrones. 2-Pyrones are known to react with alkynes in a Diels–Alder reaction to form arene compounds with expulsion of carbon dioxide, for example: [17] Pyrone cycloaddition
Benzene, the most widely recognized aromatic compound with six delocalized π-electrons (4n + 2, for n = 1). In organic chemistry , Hückel's rule predicts that a planar ring molecule will have aromatic properties if it has 4 n + 2 π-electrons , where n is a non-negative integer .
An antiaromatic compound may demonstrate its antiaromaticity both kinetically and thermodynamically. As will be discussed later, antiaromatic compounds experience exceptionally high chemical reactivity (being highly reactive is not “indicative” of an antiaromatic compound, it merely suggests that the compound could be antiaromatic).
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 ).
It is an unstable, non-planar compound which is non-aromatic. [ 1 ] [ 2 ] The dianion, however, satisfies Hückel's rule , is thermally stable, and is planar. [ 3 ]
The compound is the prototypical antiaromatic hydrocarbon with 4 pi electrons (or π electrons). It is the smallest [n]-annulene ([4]-annulene).Its rectangular structure is the result of a pseudo [3] - (or second order) Jahn–Teller effect, which distorts the molecule and lowers its symmetry, converting the triplet to a singlet ground state. [4]
Mass action (sociology), in sociology, a term for situations in which a large number of people behave simultaneously in similar ways individually and without coordination; Mass Action Principle (neuroscience), in neuroscience, the belief that memory and learning are distributed and can't be isolated within any one area of the brain
Cyclotetradecaheptaene, often referred to as [14]annulene, is a hydrocarbon with molecular formula C 14 H 14, which played an important role in the development of criteria (Hückel's rule) for aromaticity, a stabilizing property of central importance in physical organic chemistry. It forms dark-red needle-like crystals.