Number of `sp^2` hybrid carbon atoms in aspartame is

Options

A. (a) 7
B. (b) 8
C. (c) 6
D. (d) 9

Answer

To determine the number of `sp²` hybrid carbon atoms in aspartame, we will analyze its structure step by step.

### Step 1: Understand the Structure of Aspartame
Aspartame is a methyl ester of the dipeptide formed from aspartic acid and phenylalanine. To find the number of `sp²` hybridized carbon atoms, we need to draw or visualize the structure of aspartame.

### Step 2: Identify the Carbon Atoms
In the structure of aspartame, we will identify all the carbon atoms present. Aspartame consists of:
- The carbon backbone from aspartic acid.
- The carbon backbone from phenylalanine.
- The carbon from the methyl ester group.

### Step 3: Determine the Hybridization of Each Carbon Atom
To find the hybridization of each carbon atom, we can use the concept of steric number, which is calculated as:
\[ \text{Steric Number} = \text{Number of Lone Pairs} + \text{Number of Bond Pairs} \]

- **`sp²` Hybridization**: Steric number = 3 (2 single bonds and 1 double bond)
- **`sp³` Hybridization**: Steric number = 4 (4 single bonds)

### Step 4: Analyze Each Carbon Atom
1. **Carbons in the Methyl Ester Group**:
- The carbon attached to the oxygen in the methyl group (–OCH₃) is `sp³` hybridized.
- The carbon in the carbonyl group (C=O) is `sp²` hybridized.

2. **Carbons in the Aspartic Acid Backbone**:
- The carbon in the carboxylic acid group (–COOH) is `sp²` hybridized.
- The carbon connected to the amine group (–NH₂) is `sp³` hybridized.
- The carbon connecting to the methyl ester is `sp³` hybridized.

3. **Carbons in the Phenylalanine Backbone**:
- The carbons in the benzene ring are all `sp²` hybridized. There are 6 carbon atoms in the benzene ring.

### Step 5: Count the `sp²` Hybridized Carbons
Now, we will count the `sp²` hybridized carbon atoms identified:
- 1 from the carbonyl group in the methyl ester.
- 1 from the carboxylic acid group in aspartic acid.
- 6 from the benzene ring.

Total `sp²` hybridized carbon atoms = 1 (carbonyl) + 1 (carboxylic) + 6 (benzene) = **8** `sp²` hybridized carbon atoms.

### Final Answer
The number of `sp²` hybrid carbon atoms in aspartame is **8**.