Why cations are reactive chemicals

This article is cited by 26 publications. The Journal of Organic Chemistry , 84 18 , Pantazis, Giovanni Bistoni. The Journal of Physical Chemistry A , 24 , Journal of Chemical Theory and Computation , 15 3 , Journal of the American Chemical Society , 49 , The Journal of Organic Chemistry , 83 15 , Isolation of an Antiaromatic Singlet Cyclopentadienyl Zwitterion.

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Loading related content. Jump to main content. Jump to site search. You do not have JavaScript enabled. Please enable JavaScript to access the full features of the site or access our non-JavaScript page. Issue 4, From the journal: Chemical Society Reviews. Reactive p-block cations stabilized by weakly coordinating anions. Tobias A. Engesser , a Martin R. This article is part of the themed collection: Modern Main Group Chemistry.

This article is Open Access. Please wait while we load your content Something went wrong. Try again? If a double bond is adjacent to a cation, conjugation between filled and empty p orbitals allows the porisitve charge to be deistributed across multiple carbon atoms. This effect lowers the amount of positive charge borne by an one carbon atom.

They are about as stable as a secondary cation along a regular carbon chain, even if they would otherwise be only primary cations. Of course, other atoms can be cations, too. As seen above, oxygens and nitrogens are very commonly encountered as cations.

That is partly because they are very good at donating electrons to neighbouring atoms in need. Sometimes, remote groups provide additional stabilization for a cation. Indicate whether each of the following cations would be more stable or less stable than a benzyl cation, and explain why.

There are other, more subtle factors that can influence the stability of cations. Charge stability is affected by the structure further away from the atom bearing the charge. For example, a triethylammonium cation and a trimethylammonium cation look pretty similar. However, a triethlammonium cation is a little less stable than a trimethylammonium cation. The difference in these cations is related to the size of the overall molecule.

Reactions usually take place in a solvent. A cation or anion most commonly occurs in solution. Because charge stability is a big issue, the solvent will also help to stabilize the charge.

To do so, the solvent molecules will arrange themselves in a favourable way around the cation. The bigger the cation, the more solvent molecules will be needed to arrange themelves around it. Negatively charged ions are also common intermediates in reactions.

Like cations, anions are frequently unstable species. These species are stabilized by a number of different factors, not unlike cation stability. Carbanions, amide ions and alkoxide ions are examples of anionic intermediates. Remember, there are just a few key factors that explain a great deal of questions about anion stability.

Within a column of the periodic table, when comparing two atoms with negative charge, the stability of the anions principally depends on polarizability of the atom. Polarizability refers to how easily distorted the electrons are around the atom. The larger the atom, and the further the electrons from the nucleus, the more polarizable it is.

The more polarizable the atom, the more stable the anion. Within a row of the periodic table, the more electronegative an atom, the more stable the anion.