CH2NO2- Resonance structure?
The Correct Answer and Explanation is :
The chemical species ( \text{CH}_2\text{NO}_2^- ) is the conjugate base of formic acid (HCOOH), and it consists of a formate anion with a nitro group. The molecular structure consists of a central carbon (C) bonded to two hydrogen atoms and a negatively charged nitro group (NO₂⁻). The resonance structures of ( \text{CH}_2\text{NO}_2^- ) can be derived by considering the delocalization of the negative charge and double bonds between the atoms in the molecule.
Resonance Structures:
- First Resonance Structure:
- The central carbon (C) is double-bonded to oxygen (O), which is attached to a nitro group (-NO₂). The hydrogen atoms are bonded to the carbon atom.
- In this structure, the negative charge resides on the oxygen of the nitro group.
- Second Resonance Structure:
- The negative charge is delocalized and is shifted to the oxygen of the formate group (the C-O bond).
- A double bond forms between the carbon and oxygen, while the previous oxygen of the nitro group now has a single bond with nitrogen, leading to a charge separation between the two oxygen atoms.
Explanation:
In ( \text{CH}_2\text{NO}_2^- ), the negative charge is delocalized across the oxygen atoms, which results in a more stable structure due to resonance. The lone pair of electrons on the oxygen adjacent to the nitro group can delocalize into the pi system of the C=O bond. This interaction stabilizes the negative charge by spreading it over multiple atoms.
Resonance structures are a way of depicting the fact that the actual structure of the molecule is a hybrid of all possible resonance forms, rather than any one specific form. The true electron distribution is a blend of all these possibilities.
The negative charge is stabilized by the electron-withdrawing nitro group, which helps distribute the charge more effectively across the molecule. This stabilization plays an essential role in the reactivity of the formate anion in reactions such as nucleophilic substitution. The presence of resonance contributes to the overall stability of the molecule and helps in predicting its chemical behavior in different reactions.
