Functional Groups

To determine the number of secondary (2°) carbon atoms in the given compound, we need to understand the definition of a 2° carbon atom. A secondary carbon atom is a carbon atom bonded to two other carbon atoms.

Analyzing the structure, we identify the types of carbon atoms:

1. The first and last carbon atoms are primary (1°) as they are bonded only to one other carbon atom.
2. The second and fourth carbon atoms are tertiary (3°) because they are bonded to three other carbon atoms.
3. The middle (third) carbon atom is bonded to two other carbon atoms, making it a secondary (2°) carbon atom.

Therefore, the number of secondary (2°) carbon atoms in the compound is one.

Thus, the correct answer is: One.