Question

Classify each of the following hydrocarbons as alkanes, alkenes, or alkynes. (a) \(\mathrm{C}_{12} \mathrm{H}_{24}\) (b) \(\mathrm{C}_{7} \mathrm{H}_{12}\) (c) \(\mathrm{C}_{13} \mathrm{H}_{28}\)

Short answer

Question: Classify the following hydrocarbons as alkanes, alkenes, or alkynes: (a) C₁₂H₂₄, (b) C₇H₁₂, and (c) C₁₃H₂₈. Answer: (a) C₁₂H₂₄ is an alkene, (b) C₇H₁₂ is an alkyne, and (c) C₁₃H₂₈ is an alkane.

Step-by-step solution

(a) Classifying \(\mathrm{C}_{12} \mathrm{H}_{24}\)

We will compare the given formula with the general formulas for each type of hydrocarbon: 1. For alkanes, n = 12, so \(\mathrm{H}_{2n+2} = \mathrm{H}_{26}\). This does not match the given formula. 2. For alkenes, n = 12, so \(\mathrm{H}_{2n} = \mathrm{H}_{24}\). This matches the given formula, so \(\mathrm{C}_{12} \mathrm{H}_{24}\) is an alkene.

(b) Classifying \(\mathrm{C}_{7} \mathrm{H}_{12}\)

We will again compare the given formula with the general formulas for each type of hydrocarbon: 1. For alkanes, n = 7, so \(\mathrm{H}_{2n+2} = \mathrm{H}_{16}\). This does not match the given formula. 2. For alkenes, n = 7, so \(\mathrm{H}_{2n} = \mathrm{H}_{14}\). This does not match the given formula. 3. For alkynes, n = 7, so \(\mathrm{H}_{2n-2} = \mathrm{H}_{12}\). This matches the given formula, so \(\mathrm{C}_{7} \mathrm{H}_{12}\) is an alkyne.

(c) Classifying \(\mathrm{C}_{13} \mathrm{H}_{28}\)

We will again compare the given formula with the general formulas for each type of hydrocarbon: 1. For alkanes, n = 13, so \(\mathrm{H}_{2n+2} = \mathrm{H}_{28}\). This matches the given formula, so \(\mathrm{C}_{13} \mathrm{H}_{28}\) is an alkane. 2. For alkenes and alkynes, the number of hydrogen atoms will be less than 28 for n = 13, so \(\mathrm{C}_{13} \mathrm{H}_{28}\) cannot be an alkene or alkyne. From the above analysis, we classify the hydrocarbons as follows: (a) \(\mathrm{C}_{12} \mathrm{H}_{24}\) is an alkene (b) \(\mathrm{C}_{7} \mathrm{H}_{12}\) is an alkyne (c) \(\mathrm{C}_{13} \mathrm{H}_{28}\) is an alkane