Which of the following statements are correct about 18-crown-6?

Options

A. It is a cyclic polyether
B. In all, it has 18 atoms
C. It has 12 carbon atoms
D. It has 6 oxygen atoms

Answer

To determine which statements about 18-crown-6 are correct, we need to analyze its structure and properties step by step.

### Step-by-Step Solution:

1. **Understanding the Name "18-crown-6":**
- The name "18-crown-6" indicates that the molecule is a crown ether.
- The number 18 refers to the total number of atoms in the ring (both carbon and oxygen).
- The number 6 indicates that there are 6 oxygen atoms in the structure.

2. **Calculating the Number of Carbon Atoms:**
- Since there are 6 oxygen atoms in the molecule, the remaining atoms must be carbon.
- Total atoms = 18 (from the name)
- Number of carbon atoms = Total atoms - Number of oxygen atoms = 18 - 6 = 12.
- Therefore, there are 12 carbon atoms in 18-crown-6.

3. **Drawing the Structure:**
- The structure of 18-crown-6 can be visualized as a cyclic molecule where the oxygen atoms are part of the ring and are alternated with carbon atoms.
- The carbon atoms are connected by ethylene (–CH2–CH2–) units, forming a cyclic arrangement.

4. **Counting Hydrogen Atoms:**
- Each carbon in the structure can bond with 2 hydrogen atoms (since carbon has a valency of 4 and each carbon is bonded to 2 other atoms in the ring).
- Therefore, the total number of hydrogen atoms = Number of carbon atoms × 2 = 12 × 2 = 24.

5. **Total Atom Count:**
- Now, we can calculate the total number of atoms in 18-crown-6:
- Total atoms = Number of carbon atoms + Number of oxygen atoms + Number of hydrogen atoms
- Total atoms = 12 (C) + 6 (O) + 24 (H) = 42.

6. **Evaluating the Statements:**
- Now we can evaluate the given statements:
- **Statement 1:** "It is a cyclic polyether" - This is correct.
- **Statement 2:** "It has 18 atoms in all" - This is incorrect; it has 42 atoms in total.
- **Statement 3:** "It has 12 carbon atoms" - This is correct.
- **Statement 4:** "It has 6 oxygen atoms" - This is also correct.

7. **Conclusion:**
- The correct statements about 18-crown-6 are:
- Statement 1 (correct)
- Statement 3 (correct)
- Statement 4 (correct)
- Therefore, the correct options are A, C, and D.