What is the index of hydrogen deficiency (degree of unsaturation) for $C_6{H}_6$?

• A. $4$
• B. $2$
• C. $1$
• D. $3$

Answer: (A)

Verified step by step guidance

1. Identify the molecular formula given: C6H6.
2. Recall the formula for the index of hydrogen deficiency (IHD), also known as the degree of unsaturation: \(IHD = \frac{2C + 2 - H}{2}\) where \(C\) is the number of carbons and \(H\) is the number of hydrogens in the molecule.
3. Substitute the values from the molecular formula into the formula: \(IHD = \frac{2 \times 6 + 2 - 6}{2}\)
4. Simplify the numerator first: \$2 \times 6 = 12\(, so the numerator becomes \)12 + 2 - 6$.
5. Calculate the final value of the numerator and then divide by 2 to find the IHD, which tells you the total number of rings and/or multiple bonds present in the molecule.