Select the most stable carbonium ion from amongst the following

Options

A.
B.
C.
D.

Answer

To determine the most stable carbonium ion from the given options, we need to analyze the structure of each carbonium ion and the substituents attached to the positively charged carbon atom. The stability of carbonium ions (also known as carbocations) is influenced by the number and type of substituents attached to the positively charged carbon. Here’s a step-by-step solution:

### Step 1: Identify the Carbonium Ions
First, we need to identify the structures of the carbonium ions provided in the options. Each carbonium ion has a positive charge on a carbon atom.

### Step 2: Understand the Stability Factors
The stability of carbonium ions is primarily influenced by:
- **Alkyl Substitution**: More alkyl groups attached to the positively charged carbon increase stability due to the +I (inductive) effect.
- **Electron Donating Effects**: Groups that can donate electron density (like alkyl groups) stabilize the positive charge.

### Step 3: Analyze Each Option
Let’s analyze the options based on the number of alkyl groups attached to the positively charged carbon:

1. **Option A**: Has one alkyl group attached.
2. **Option B**: Has three alkyl groups attached.
3. **Option C**: Has two alkyl groups attached.
4. **Option D**: Has one alkyl group attached.

### Step 4: Count the +I Effects
- **Option A**: 1 +I effect from one alkyl group.
- **Option B**: 3 +I effects from three alkyl groups.
- **Option C**: 2 +I effects from two alkyl groups.
- **Option D**: 1 +I effect from one alkyl group.

### Step 5: Determine the Most Stable Carbonium Ion
From the analysis:
- **Option B** has the highest number of +I effects (3), which means it has the most electron-donating groups stabilizing the positive charge. Therefore, it is the most stable carbonium ion.

### Conclusion
The most stable carbonium ion among the options is **Option B**.

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