Which of the following will have weakest indicated C-H bond?

Options

A.
B.
C.
D. `CH_(3)-H`

Answer

To determine which compound has the weakest indicated C-H bond, we need to analyze the influence of substituents on the stability of the resulting carbon ion formed when the C-H bond is broken. Here's a step-by-step breakdown of the solution:

### Step 1: Identify the Compounds
We need to look at the given compounds and identify the indicated C-H bond in each.

### Step 2: Break the C-H Bond
When we break the C-H bond in each compound, we will form a carbon ion (negatively charged carbon). For example, if we take compound A, breaking the C-H bond will yield a carbon ion with a negative charge.

### Step 3: Analyze the Effect of Substituents
- **Compound A**: The carbon ion formed will have a nitro group (NO2) attached. The nitro group is an electron-withdrawing group, which stabilizes the negative charge on the carbon ion. This stabilization makes it easier to break the C-H bond.

- **Compound B**: This compound has multiple alkyl groups (CH3). Alkyl groups are electron-donating groups, which destabilize the negative charge on the carbon ion. Therefore, the C-H bond in this compound is stronger and less likely to break.

- **Compound C**: Similar to compound B, this compound also has multiple alkyl groups that destabilize the carbon ion, making the C-H bond stronger.

- **Compound D**: This compound has no stabilizing groups, and the carbon ion formed will be unstable due to the lack of resonance or electron-withdrawing effects.

### Step 4: Compare the Stability of Carbon Ions
The stability of the carbon ions formed from each compound is crucial:
- The carbon ion from **Compound A** is stabilized by the electron-withdrawing nitro group.
- The carbon ions from **Compounds B, C, and D** are destabilized by electron-donating groups or lack of stabilizing factors.

### Step 5: Determine the Weakest C-H Bond
Since the C-H bond in **Compound A** can be broken more easily due to the stabilization of the resulting carbon ion, it has the weakest indicated C-H bond among the compounds.

### Conclusion
The compound with the weakest indicated C-H bond is **Compound A** due to the presence of the electron-withdrawing nitro group, which stabilizes the negative charge on the carbon ion formed upon breaking the bond.

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