Which one of the following behaves both as a nucleophile and an electrophile ?

Options

A. Acetone
B. Cyanide ion
C. Nitrite ion
D. Sulphite ion

Answer

To determine which compound behaves both as a nucleophile and an electrophile, we need to analyze the characteristics of each type of species:

### Step 1: Understand the definitions
- **Nucleophiles** are electron-rich species that can donate a pair of electrons. They are often negatively charged or have lone pairs of electrons.
- **Electrophiles** are electron-deficient species that can accept a pair of electrons. They are often positively charged or have a partial positive charge.

### Step 2: Analyze the options
Let's consider the example of **acetone (CH3COCH3)**:
- The structure of acetone shows that it has a carbonyl group (C=O).
- The oxygen atom in the carbonyl group has two lone pairs of electrons, making it capable of donating electrons. This characteristic allows acetone to act as a nucleophile.
- The carbon atom in the carbonyl group is bonded to the more electronegative oxygen, leading to a partial positive charge (δ+) on the carbon. This makes the carbon atom an electrophilic center.

### Step 3: Conclusion about acetone
Since acetone can donate electrons through the oxygen (acting as a nucleophile) and has a positively charged carbon (acting as an electrophile), it fulfills the criteria for both roles.

### Step 4: Evaluate other options
- **Cyanide ion (CN⁻)**: This species has a negative charge and acts only as a nucleophile.
- **Nitrite ion (NO2⁻)**: This species also has a negative charge and acts only as a nucleophile.
- **Sulfite ion (SO3²⁻)**: This species has a negative charge and acts only as a nucleophile.

### Final Answer
The correct answer is **acetone (CH3COCH3)**, as it behaves both as a nucleophile and an electrophile.

---