Number of `sp_2` hybrid carbon atoms in aspartame is

Explanation

To determine the number of sp² hybridized carbon atoms in aspartame, we will follow these steps:

### Step 1: Understand the Structure of Aspartame
Aspartame is formed from the reaction of aspartic acid and phenylalanine. We need to visualize or draw the structure of aspartame to identify the carbon atoms.

### Step 2: Draw the Structure of Aspartame
1. **Aspartic Acid Structure**:
- The structure of aspartic acid is:
```
HOOC-CH(NH2)-CH2-COOH
```
2. **Phenylalanine Structure**:
- The structure of phenylalanine is:
```
C6H5-CH2-CH(NH2)-COOH
```
3. **Combine the Structures**:
- When aspartic acid reacts with phenylalanine, the carboxylic acid group (–COOH) of aspartic acid and the hydrogen from the amine group (–NH2) of phenylalanine are removed to form aspartame. The structure of aspartame can be represented as:
```
C6H5-CH(NH2)-CO-CH2-COOH
```

### Step 3: Identify sp² Hybridized Carbons
1. **Definition of sp² Hybridization**:
- A carbon atom is sp² hybridized if it is bonded to three other atoms and has one double bond.

2. **Locate sp² Carbons in Aspartame**:
- In the structure of aspartame, we look for carbon atoms that are involved in double bonds or are bonded to three other atoms.
- The carbonyl groups (C=O) in the structure contribute to sp² hybridization.
- The phenyl ring (C6H5) contains 6 sp² hybridized carbon atoms.

### Step 4: Count the sp² Hybridized Carbons
1. **Count from the Phenyl Ring**:
- The phenyl ring has 6 sp² hybridized carbon atoms.

2. **Count from the Carbonyl Groups**:
- There are 3 additional sp² hybridized carbon atoms from the carbonyl groups (C=O) in aspartame.

### Step 5: Total Count of sp² Hybridized Carbons
- Total sp² hybridized carbon atoms = 6 (from phenyl) + 3 (from carbonyls) = **9 sp² hybridized carbon atoms**.

### Final Answer
The number of sp² hybridized carbon atoms in aspartame is **9**.

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