On p. 429, when introducing the idea of bromonium ions, Clayden et. al.[1] mention that:

You can think of the bromonium ion as a carbocation that has been stabilised by interaction with a nearby bromine atom. You have seen a similar effect - this 'oxonium ion' was an intermediate, for example, in the $\ce {S_N1}$ substitution of MOM chloride on p. 338 of Chapter 15.

This carbocation stabilisation described in the text above is illustrated in the image below. The case described seems to be that of an adjacent carbon with a positive charge. However, I was wondering if a carbon one atom away with a positive charge could be stabilised in the same manner as well. This would be more similar to the bromonium ion. I have illustrated what I am referring to in the image below.

I would like to ask if this "interesting oxonium ion", as an oxygen analogue of the bromonium ion, does exist in reactions, such as $\ce {S_N1}$ substitutions.


  1. Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed.; Oxford UP: Oxford, U.K., 2012.
  • $\begingroup$ Could you please be a bit clearer? I didn't understand what you are asking. $\endgroup$ – Eashaan Godbole Jan 7 '18 at 5:47
  • $\begingroup$ @EashaanGodbole I have edited to clarify my question $\endgroup$ – Tan Yong Boon Jan 7 '18 at 6:01
  • $\begingroup$ there were NMR studies dating back at least to 1966 pubs.acs.org/doi/abs/10.1021/ja00965a030?journalCode=jacsat $\endgroup$ – permeakra Jan 7 '18 at 6:23
  • $\begingroup$ These should form in SN-NGP reactions too $\endgroup$ – Eashaan Godbole Jan 7 '18 at 10:20
  • $\begingroup$ That's quite common type of oxonium cation, there are more interesting ones. Also title is rather ambiguous now. $\endgroup$ – Mithoron Jan 7 '18 at 16:23

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