Among the following the dissociation constant is highest for

Options

A. `C_(6)H_(5)OH`
B. `C_(6)H_(5)CH_(2)OH`
C. `CH_(3)C-=CH`
D. `CH_(3)NH_(3)^(+)Cl^(-)`

Explanation

To determine which compound has the highest dissociation constant (Ka), we need to analyze the compounds given and their ability to lose a proton (H+). The dissociation constant is a measure of how easily a compound can dissociate into its ions in solution.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds mentioned in the question are:
- C6H5OH (Phenol)
- C6H5CH2OH (Benzyl alcohol)
- CH3C≡CH (Alkyne)
- CH3NH3+Cl- (Methylammonium chloride)

2. **Understand the Concept of Dissociation Constant**: The dissociation constant (Ka) is higher for compounds that can easily lose a proton. Conversely, compounds that hold onto their protons more tightly will have lower Ka values.

3. **Analyze Each Compound**:
- **C6H5OH (Phenol)**: This compound can lose a proton, but the presence of the aromatic ring stabilizes the remaining negative charge, making it relatively easier to lose the proton. However, it still forms hydrogen bonds, which can stabilize the molecule.
- **C6H5CH2OH (Benzyl alcohol)**: Similar to phenol, this compound can also lose a proton. However, it is an alcohol and tends to form hydrogen bonds, making the loss of a proton easier than in more acidic compounds.
- **CH3C≡CH (Alkyne)**: The hydrogen attached to the terminal carbon in alkynes is more acidic than those in alcohols and phenols. This means it can lose a proton more easily, but it is still not as acidic as ammonium ions.
- **CH3NH3+Cl- (Methylammonium chloride)**: This compound contains an ammonium ion (CH3NH3+), which is a positively charged species. The hydrogen in this ion is less likely to be removed due to the positive charge and the electron-withdrawing effects of the nitrogen atom, making it more stable and thus having a higher dissociation constant.

4. **Conclusion**: Among the four compounds, CH3NH3+Cl- has the highest dissociation constant because the removal of the proton from the ammonium ion is more difficult due to the stabilizing effects of the nitrogen atom and the positive charge.

### Final Answer:
The dissociation constant is highest for **CH3NH3+Cl-**.