Question

Identify the hetero atom and number of double bonds respectively present in furan?

• A. S, 2
• B. O, 2
• C. N, 2
• D. O, 1

Hint:

To remember the core five-membered heterocycles easily, associate them directly with their single heteroatom: Furan contains Oxygen, Thiophene contains Sulfur, and Pyrrole contains Nitrogen!

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks us to identify the specific heteroatom embedded within the cyclic ring structure of furan and determine the total number of carbon-carbon double bonds present inside it.

Step 2: Key Formula or Approach:
Furan is a fundamental heterocyclic aromatic organic compound. A heterocyclic compound is a cyclic structure that contains at least one atom other than carbon (known as a heteroatom) within its ring loop.

Step 3: Detailed Explanation:
Let's analyze the molecular architecture of furan ($\text{C}_4\text{H}_4\text{O}$):
It consists of a five-membered planar ring system.
Four vertices of this ring are occupied by $\text{sp}^2$ hybridized carbon atoms, and the fifth vertex is occupied by a single oxygen atom (O), making oxygen the defining heteroatom.
Alternating along the carbon segments are exactly two conjugated carbon-carbon double bonds (C=C).
To satisfy aromatic stability ($6\pi$-electrons), one of the two unshared lone pairs on the oxygen atom delocalizes into the cyclic ring cloud, complementing the four electrons provided by the two double bonds ($4 + 2 = 6$).
Thus, the heteroatom is Oxygen (O) and the count of double bonds is 2, which matches option (B).

Step 4: Final Answer:
The heteroatom and number of double bonds in furan are O and 2, corresponding to option (B).