Which of the following is the most stable Cation

Options

A. `CH_(3) overset(+)(C)H_(2)`
B. `CH_(3) overset(+)(C)HCH_(3)`
C. `CH_(3) overset(+)(C)H C_(6)H_(5)`
D. `C_(6)H_(5)CH_(2) overset(+)(C)H_(2)`

Explanation

To determine which cation is the most stable among the given options, we need to analyze the stability of cations based on their structure and the presence of electron-donating groups. Here’s a step-by-step solution:

### Step 1: Understand what a cation is
A cation is a positively charged ion that has a deficiency of electrons. This deficiency makes cations generally unstable, and their stability can be influenced by surrounding groups.

**Hint:** Remember that cations are electron-deficient species and their stability can be enhanced by electron-donating groups.

### Step 2: Identify electron-donating groups
Electron-donating groups (EDGs) can stabilize cations by donating electron density to the positively charged carbon. Common EDGs include alkyl groups (like CH3) and groups with lone pairs (like -OH, -O-).

**Hint:** Look for groups that can donate electrons to the cation to enhance its stability.

### Step 3: Analyze the given cations
1. **First cation:** CH2^+ (only one electron-donating group)
2. **Second cation:** CH^+ with two CH3 groups (more electron-donating groups)
3. **Third cation:** CH^+ attached to a benzene ring (resonance stabilization)
4. **Fourth cation:** CH^+ attached to a carbon chain and a benzene ring (limited resonance)

**Hint:** Count the number of electron-donating groups for each cation and consider resonance effects.

### Step 4: Evaluate resonance stabilization
The third cation, which has a positive charge adjacent to a benzene ring, can delocalize the positive charge through resonance. This means that instead of being localized on one carbon, the charge can be spread out over multiple atoms, significantly increasing stability.

**Hint:** Resonance can greatly enhance stability; look for structures that allow for charge delocalization.

### Step 5: Compare the stability of each cation
- The first cation has minimal stabilization due to only one EDG.
- The second cation is more stable than the first due to two EDGs.
- The third cation is the most stable due to resonance with the benzene ring.
- The fourth cation has limited resonance and is less stable than the third.

**Hint:** The presence of resonance is a key factor in determining the stability of cations.

### Conclusion
The most stable cation among the options is the third cation, which is stabilized by resonance with the benzene ring.

**Final Answer:** The third cation is the most stable.