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However, the cyclopropenyl anion has 4 π electrons in a cyclic system and in fact has a substantially higher pK a than 1-propene because it is antiaromatic and thus destabilized. [3] Because antiaromatic compounds are often short-lived and difficult to work with experimentally, antiaromatic destabilization energy is often modeled by simulation ...
In 2011, Jordi Poater and Miquel Solà expanded the rule to open-shell spherical compounds, finding they were aromatic when they had 2n 2 + 2n + 1 π-electrons, with spin S = (n + 1/2) - corresponding to a half-filled last energy level with the same spin. For instance C 60 1– is also observed to be aromatic with a spin of 11/2. [16]
Aromaticity is found in ions as well: the cyclopropenyl cation (2e system), the cyclopentadienyl anion (6e system), the tropylium ion (6e), and the cyclooctatetraene dianion (10e). Aromatic properties have been attributed to non-benzenoid compounds such as tropone .
Homoaromaticity, in organic chemistry, refers to a special case of aromaticity in which conjugation is interrupted by a single sp 3 hybridized carbon atom. Although this sp 3 center disrupts the continuous overlap of p-orbitals, traditionally thought to be a requirement for aromaticity, considerable thermodynamic stability and many of the spectroscopic, magnetic, and chemical properties ...
The cyclopentadienyl anion is a planar, cyclic, regular-pentagonal ion; it has 6 π-electrons (4n + 2, where n = 1), which fulfills Hückel's rule of aromaticity. Each double bond and lone pair provides 2 π-electrons, which are delocalized into the ring. [4] Cyclopentadiene has a pKa of about 16. It is acidic relative to many carbon acids.
3 Cyclopropenyl anion. 2 comments. 4 Peer review and responses during the educational assignment in Fall 2013. 5 Peer Review 1. 1 comment Toggle Peer Review 1 subsection.
The radical anion is also known. [1] The dianion was first synthesized by reacting triquinacene with n-butyllithium and potassium tert-amylate (also called potassium t-pentoxide) in hexane solution. [2] [3]
Both the B 3 + fragment and the B 3 R 3 2− fragment (with electron-sharing B−R bonds) are Hückel-aromatic forms of the triboracyclopropenyl fragment.. The triboracyclopropenyl fragment is a cyclic structural motif in boron chemistry, named for its geometric similarity to cyclopropene.