From their molecular formulas, classify each of these...

From their molecular formulas, classify each of these straight-chain hydrocarbons as an alkane, an alkene, or an alkyne.
(a) $\mathrm{C}_{5} \mathrm{H}_{8}$
(b) $\mathrm{C}_{24} \mathrm{H}_{50}$
(c) $\mathrm{C}_{7} \mathrm{H}_{14}$

Key Concepts

Hydrocarbon Classification

Hydrocarbon classification involves categorizing compounds that consist solely of carbon and hydrogen. These compounds are primarily divided into saturated and unsaturated varieties based on the types of bonds present between carbon atoms. This classification helps chemists predict reactivity, physical properties, and methods of chemical synthesis.

Alkanes

Alkanes are the simplest form of hydrocarbons and are fully saturated, meaning that they contain only single bonds between carbon atoms. Their general molecular formula is C?H????, which reflects the maximum number of hydrogen atoms bonded to each carbon. This saturation results in relatively inert chemical properties compared to unsaturated hydrocarbons.

Alkenes

Alkenes are unsaturated hydrocarbons that contain at least one carbon–carbon double bond. Their general formula is C?H??, indicating a deficiency of two hydrogen atoms compared to alkanes. The presence of the double bond not only defines their structure but also makes alkenes more reactive, particularly in addition reactions.

Alkynes

Alkynes are another type of unsaturated hydrocarbons characterized by the presence of at least one carbon–carbon triple bond. Their general formula is C?H????, showing a loss of four hydrogen atoms relative to alkanes. The triple bond in alkynes contributes to their unique reactivity and geometry, often making them useful intermediates in organic synthesis.

Degree of Unsaturation

The degree of unsaturation is a concept used to determine the number of rings and multiple bonds present in a molecule by comparing its molecular formula to that of a completely saturated hydrocarbon. Each degree of unsaturation corresponds to either one double bond or one ring, while a triple bond counts as two degrees. This tool is essential for inferring structural details from a molecular formula.

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