Search results
Results from the WOW.Com Content Network
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]
With two π electrons, the cyclopropenium cation class obeys Hückel’s rules of aromaticity for 4n + 2 electrons since, in this case, n = 0. Consistent with this prediction, the C 3 H 3 core is planar and the C–C bonds are equivalent. In the case of the cation in [C 3 (SiMe 3) 3] + SbCl − 6, [3] the ring C–C distances range from 1.374(2 ...
In contrast to the rarity of Möbius aromatic ground state molecular systems, there are many examples of pericyclic transition states that exhibit Möbius aromaticity. The classification of a pericyclic transition state as either Möbius or Hückel topology determines whether 4N or 4N + 2 electrons are required to make the transition state aromatic or antiaromatic, and therefore, allowed or ...
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 ...
[1] [2] The lowest triplet state of an annulene is, according to Baird's rule, aromatic when it has 4n π-electrons and antiaromatic when the π-electron count is 4n + 2, where n is any positive integer. This trend is opposite to that predicted by Hückel's rule for the ground state, which is usually the lowest singlet state (S 0).
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.
Instead, however, the structure has a dominant partially-delocalized charge-separated structure consisting of four independently-aromatic (4n+2 π electron) rings: two as cyclopropenyl cations (two π electrons each) and two as cyclopentadienyl anions (six π electrons each). [2] cis-Bicalicene, by contrast, is an antiaromatic hydrocarbon. [3 ...