Palmitic and arachidonic acid have how many carbons excluding the carboxyl carbon?

Options

A. 16,18
B. 16,20
C. 15,19
D. 15,20

Answer

To determine the number of carbons in palmitic and arachidonic acid, excluding the carboxyl carbon, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Chemical Structures**:
- Palmitic acid is a saturated fatty acid with the chemical formula C16H32O2.
- Arachidonic acid is a polyunsaturated fatty acid with the chemical formula C20H32O2.

2. **Understand the Carboxyl Group**:
- Both acids contain one carboxyl group (COOH), which contributes one carbon atom to the total count.

3. **Calculate Carbons in Palmitic Acid**:
- Total carbons in palmitic acid = 16 (from C16H32O2).
- Excluding the carboxyl carbon: 16 - 1 = 15.
- Therefore, palmitic acid has **15 carbons** excluding the carboxyl carbon.

4. **Calculate Carbons in Arachidonic Acid**:
- Total carbons in arachidonic acid = 20 (from C20H32O2).
- Excluding the carboxyl carbon: 20 - 1 = 19.
- Therefore, arachidonic acid has **19 carbons** excluding the carboxyl carbon.

5. **Summarize the Results**:
- Palmitic acid: 15 carbons (excluding the carboxyl carbon).
- Arachidonic acid: 19 carbons (excluding the carboxyl carbon).

6. **Select the Correct Option**:
- The correct answer is **15 and 19** for palmitic and arachidonic acid, respectively.

### Final Answer:
- The number of carbons excluding the carboxyl carbon in palmitic acid is 15, and in arachidonic acid is 19.