Cho các hợp chất có công thức sau: CH3COOC2H5, CH3COOH, CH3COCH3, H2NCH2COOH, C6H5COOCH3, HCOONH3CH3, HCOOCH=CH2. Có bao nhiêu hợp chất là ester?

Đáp án: 3

Phân tích từng chất:

1. $\text{C}\text{H}{}_3\text{C}\text{O}\text{O}\text{C}{}_2\text{H}{}_5$: Ester. [✓]

2. $\text{C}\text{H}{}_3\text{C}\text{O}\text{O}\text{H}$: Acid carboxylic. [✗]

3. $\text{C}\text{H}{}_3\text{C}\text{O}\text{C}\text{H}{}_3$: Ketone. [✗]

4. $\text{H}{}_2\text{N}\text{C}\text{H}{}_2\text{C}\text{O}\text{O}\text{H}$: Amino acid. [✗]

5. $\text{C}{}_6\text{H}{}_5\text{C}\text{O}\text{O}\text{C}\text{H}{}_3$: Ester. [✓]

6. $\text{H}\text{C}\text{O}\text{O}\text{N}\text{H}{}_3\text{C}\text{H}{}_3$: Muối ammonium. [✗]

7. $\text{H}\text{C}\text{O}\text{O}\text{C}\text{H}\text{=}\text{C}\text{H}{}_2$: Ester. [✓]

$\Rightarrow$ Có 3 hợp chất là ester.