There are some non-classical carbocations, such as the 2-norbornyl cation, in which the positive charge is heavily delocalised. Have non-classical carbanions also been discovered? I have not seen any non-classical carbanions in books. If there are any non-classical carbanions, please provide some examples.

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    – orthocresol
    Dec 24, 2018 at 2:26

2 Answers 2


Interesting question. It is much less studied and reported on than the case of non-classical carbocations, but I did find a few papers. Brown and Occolowitz (Ref.1) reported that deuterated bicyclo[3.2.1]octa-2,6-diene 1b, below, undergoes base-catalysed de-deuteration (potassium tert-butoxide in DMSO) to give 1a much faster (ca. $3 \times 10^4$) than the bicyclo[3.2.1]octa-2-ene counterpart, i.e. 2b $\rightarrow$ 2a. They suggested this is evidence for the intermediacy of a 6π-electron, delocalised (non-classical) carbanion 3.


Much more recently, Brown reviewed and provided additional DFT computational evidence for stabilisation and charge delocalisation in these species (Ref.2).


  1. J. M. Brown, J. L. Occolowitz, “A non-classical carbanion,” Chem. Commun. (London) 1965, (16), 376-377 (https://doi.org/10.1039/C19650000376).
  2. John M. Brown, “Origins of Stabilization and Evidence for Charge Delocalization in the Bicyclo[3.2.1]octadienyl Anion and Related Species,” Australian Journal of Chemistry 2014, 67(9), 1296-1300 (https://doi.org/10.1071/CH14244).
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    – Micelle
    May 15, 2020 at 17:41

In addition to the species mentioned in the answer above, I found another one in Organic Chemistry by Morrison and Boyd(Seventh Edition)enter image description here


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