For 1-methoxy-1, 3-butadiene, which of the following resonating structure is least stable?

Options

A. `overset()(C)H_(2)-overset(o+)(C)H-CH=CH-O-CH_(3)`
B. `overset()(C)H_(2)-CH=CH-CH=overset(o+)(O)-CH_(3)`
C. `CH_(2)=CH-overset(o+)(C)H=overset()(C)H-O-CH_(3)`
D. `CH_(2)=CH-overset()(C)H-CH=overset(o+)(O)-CH_(3)`

Answer

To determine which resonating structure of 1-methoxy-1,3-butadiene is the least stable, we can follow these steps:

### Step 1: Identify the Resonating Structures
First, we need to identify the different resonating structures of 1-methoxy-1,3-butadiene. The structures typically involve the movement of electrons, which can lead to different charge distributions.

### Step 2: Analyze Charge Distribution
Next, we analyze the charge distribution in each resonating structure. We look for the presence of positive and negative charges and their locations, particularly focusing on electronegative atoms like oxygen.

### Step 3: Evaluate Stability Based on Charge
- **High Electronegativity and Positive Charge**: If a highly electronegative atom (like oxygen) carries a positive charge, it is generally unstable. This is because electronegative atoms prefer to hold onto electrons rather than lose them.
- **Negative Charge on Electronegativity Atom**: Conversely, if a negative charge is on an electronegative atom, it is more stable since the atom can accommodate the extra electron.

### Step 4: Compare Structures
From the analysis, we compare the stability of the resonating structures:
- Structures with positive charges on oxygen (like options 2 and 4) are less stable.
- Among these, the structure with more charge separation (option 2) will be the least stable.

### Step 5: Conclusion
Based on the analysis, the least stable resonating structure for 1-methoxy-1,3-butadiene is option 2, as it has a positive charge on the electronegative oxygen and exhibits significant charge separation.

---