I've been studying electrophiles and nucleophiles recently, including how the carbonate ion ($\ce{CO3^2-}$) is stabilised through resonance. While drawing the model for bicarbonate, however, I suddenly asked myself why a different design of this ion would not be possible. The design I am proposing features the hydrogen atom attached to the carbon, with single bonds for all of the three oxygens. This is shown below:

Alternative Design of the Bicarbonate Ion

Now, I know that this is not what we usually see, which is:

Standard Design of the Bicarbonate Ion

The question is, why is my own design not feasible? If it is, is it not energetically favourable due to the numerous charges that would have to be created?


1 Answer 1


First of all I appreciate your effort to think out of the box.

Now, as you are thinking of a new structure for the bicarbonate ion, you just have to compare the stability factors between the two different structures and you'll get your answer!

Here let's compare the structures:

Stability factors for the conventional structure

  1. Octet saturation in case of each of the element.

  2. Resonance stability (moreover, two equivalent canonical structures give more stability) in the molecule.

  3. The negative charge resides on the more electronegative $\ce{O}$ atom.

Unstability factors for your proposed structure

  1. Octet unsaturated in case of the positively charged $\ce{O}$ atom.

  2. No resonance stabilisation in the molecule.

  3. (your point) Energetically disfavoured due to numerous charge accumulation.

  4. The positive charge resides on the more electronegative $\ce{O}$ atom.

That's why your proposed structure isn't the actual structure of bicarbonate ion.


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