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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.
The cyclopentadienyl anion (C 5 H – 5) with six π electrons is planar and readily generated from the unusually acidic cyclopentadiene (pK a 16), while the corresponding cation with four π electrons is destabilized, being harder to generate than a typical acyclic pentadienyl cations and is thought to be antiaromatic. [8] Similarly, the ...
The cyclopentadienyl cation is another textbook example of an antiaromatic compound. It is conventionally understood to be planar, cyclic, and have 4 π electrons (4n for n=1) in a conjugated system. However, it has long been questioned if the cyclopentadienyl cation is genuinely antiaromatic and recent discoveries have suggested that it may ...
Cyclopentadienyl can refer to Cyclopentadienyl anion, ... Cyclopentadienyl cation, [C 5 H 5] + See also. Pentadienyl This page was last edited on 3 July 2021 ...
In chemistry, cyclopentadienyl is a radical with the formula C 5 H 5. The related cyclopentadienyl anion (which can formally be converted to the cyclopentadienyl radical by one-electron reduction) is aromatic , and forms salts and coordination compounds .
The compound is unusually acidic (pK a = 16) for a hydrocarbon, a fact explained by the high stability of the aromatic cyclopentadienyl anion, C 5 H − 5. Deprotonation can be achieved with a variety of bases, typically sodium hydride, sodium metal, and butyl lithium.
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. Aromatic properties are tested to the limit in a class of compounds called ...
Since borole dianions are isoelectronic to the ubiquitous cyclopentadienyl anion, aromatic delocalisation of the 6π electrons should cause bond lengths assimilation within the BC 4 backbone. This is exactly what was found for several characterised structures, namely K 2 [PhBC 4 Ph 4], K 2 [(4-Me 3 Si-C 6 H 4)BC 4 Ph 4] and K 2 [ClBC 4 Ph 4 ...