Question

You are given the following molecular formulae of some hydrocarbons:

C₅H₈; C₇H₁₄; C₆H₆; C₅H₁₀; C₇H₁₂; C₆H₁₂

1. Which formula represents cyclohexane as well as hexene?
2. Which formula represents benzene?
3. Which three formulae represent open chain unsaturated hydrocarbons having double bonds?
4. Which two formulae represent unsaturated hydrocarbons having triple bonds?
5. Which three formulae can represent cyclic hydrocarbons?

Answer 1

1. C₆H₁₂ is the chemical formula that denotes both cyclohexane and hexene. The chemical formula for both hexene and cyclohexane is the same, comprising six carbon atoms. Nonetheless, their structures diverge: in a cyclic molecule, the carbon atoms form a closed chain, whereas hexene has an open-chain structure.
2. C₆H₆ is the chemical formula for benzene. Benzene is an unsaturated cyclic hydrocarbon composed of six carbon atoms and six hydrogen atoms.
3. C₇H₁₄, C₅H₁₀, and C₆H₁₂ are the molecular formulas of open-chain unsaturated hydrocarbons containing double bonds, corresponding to the general formula for alkenes, C_nH_2n, where n is the number of carbon atoms in a single molecule.
4. C₅H₈ and C₇H₁₂ are the molecular formulas of unsaturated hydrocarbons containing triple bonds, consistent with the general formula for alkynes, C_nH_2n−2, where n represents the number of carbon atoms in a single molecule.
5. C₇H₁₄, C₅H₁₀, and C₆H₁₂ are three molecular formulas of cyclic hydrocarbons, consistent with the general formula C_nH_2n, where n denotes the number of carbon atoms in a single molecule. The closed chains of cyclic hydrocarbons comprise a number of carbon atoms corresponding to their chemical formulas. A cyclic hydrocarbon with 7 carbon atoms is termed cycloheptane, one with 5 carbon atoms forms a pentagonal ring known as cyclopentane, and a cyclic hydrocarbon with 6 carbon atoms is referred to as cyclohexane.