Least contributing resonating structure of nitroethene is :

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Answer

To determine the least contributing resonating structure of nitroethene (CH3CH2NO2), we need to analyze the possible resonating structures and their stability. Here’s a step-by-step solution:

### Step 1: Identify the Structure of Nitroethene
Nitroethene is derived from ethene (C2H4) with a nitro group (NO2) attached. The molecular formula is CH3CH2NO2.

### Step 2: Draw Possible Resonating Structures
Resonating structures are different ways of drawing the same molecule where the placement of electrons varies, but the arrangement of atoms remains the same. For nitroethene, we can draw several resonating structures by shifting electrons in the nitro group and the carbon skeleton.

### Step 3: Analyze Stability of Each Resonating Structure
1. **Structure with a positive and negative charge**: This is generally stable because the charges are balanced.
2. **Structure with two positive charges on adjacent atoms**: This is highly unstable due to the repulsion between like charges.
3. **Structure with alternating positive and negative charges**: This is stable due to the separation of charges.
4. **Structure with charges far apart**: This is also stable as the charges do not interact strongly.

### Step 4: Identify the Least Contributing Structure
Among the structures analyzed, the one with two positive charges on adjacent atoms is the least stable due to the high energy associated with like charges being close together. Therefore, this structure is the least contributing resonating structure.

### Conclusion
The least contributing resonating structure of nitroethene is the one that has two positive charges on adjacent atoms.

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