Question

Several studies have shown that b-carotene, a precursor of vitamin A, may play a role in preventing cancer. b-Carotene has a molecular formula of C₄₀H₅₆, and it contains two rings and no triple bonds. How many double bonds does it have?

Short answer

11 double bonds.

Step-by-step solution

Given

• Molecular formula of b-Carotene = C₄₀H₅₆
• b-Carotene contains two rings and no triple bonds.

Determination of double bonds in b-Carotene-

• C₄₀H₈₂ is the chemical formula for a hydrocarbon with no rings and no double bonds.

• There are 26 fewer hydrogens in C₄₀H₅₆.

• As a result, b-Carotene has 13 rings and double bonds in total.

• We know it has 11 double bonds since it has two rings.