Resonance in carbonate ion (CO_3 ^2-) is Which of the following is true?

CO_3 ^2- has a single structure i.e., resonance hybrid of the above three structures.

It is possible to identify each structure individually by some physical or chemical method.

All these structures are in dynamic equilibrium with each other.

Each structure exists for equal amount of time.

Basics of Organic Chemistry PYQ — JEE Main 2023 · 1 Feb · Shift 1 · Q6 with Solution

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Correct answer: D

Understand resonance in $\mathrm{CO_3^{2-}}$

The carbonate ion can be represented by three canonical (resonance) structures, where the double bond between C and O is shown with a different oxygen each time.

However, these are not real, separately existing molecules. They are only contributing structures used to describe the actual electronic structure.
What is the actual structure?

The real carbonate ion is a resonance hybrid of all the canonical structures.
- All three C–O bonds are equivalent.
- Each bond has bond order $\dfrac{4}{3}$ .
- Negative charge is delocalized over the three oxygen atoms.
Check each option

A: It is possible to identify each structure individually by some physical or chemical method.
- False. Individual resonance structures do not exist separately and cannot be isolated or identified individually.
B: All these structures are in dynamic equilibrium with each other.
- False. Resonance is not an equilibrium between real structures. The ion does not keep changing from one structure to another.
C: Each structure exists for equal amount of time.
- False. Resonance structures do not independently exist in time.
D: $\mathrm{CO_3^{2-}}$ has a single structure i.e., resonance hybrid of the above three structures.
- True. This is the correct description.
Conclusion

The correct option is: $\boxed{\text{D}}$

View written solutionFree

Correct answer: D

Understand resonance in $\mathrm{CO_3^{2-}}$

The carbonate ion can be represented by three canonical (resonance) structures, where the double bond between C and O is shown with a different oxygen each time.

However, these are not real, separately existing molecules. They are only contributing structures used to describe the actual electronic structure.
What is the actual structure?

The real carbonate ion is a resonance hybrid of all the canonical structures.
- All three C–O bonds are equivalent.
- Each bond has bond order $\dfrac{4}{3}$ .
- Negative charge is delocalized over the three oxygen atoms.
Check each option

A: It is possible to identify each structure individually by some physical or chemical method.
- False. Individual resonance structures do not exist separately and cannot be isolated or identified individually.
B: All these structures are in dynamic equilibrium with each other.
- False. Resonance is not an equilibrium between real structures. The ion does not keep changing from one structure to another.
C: Each structure exists for equal amount of time.
- False. Resonance structures do not independently exist in time.
D: $\mathrm{CO_3^{2-}}$ has a single structure i.e., resonance hybrid of the above three structures.
- True. This is the correct description.
Conclusion

The correct option is: $\boxed{\text{D}}$