Which of the following is an example of an unsaturated hydrocarbon compound?

An unsaturated hydrocarbon compound is characterized by the presence of at least one double or triple bond between carbon atoms, which lowers the number of hydrogen atoms connected to the carbon chain. Ethene, commonly known as ethylene, is a classic example of an unsaturated hydrocarbon because it contains a double bond between two carbon atoms. This double bond signifies that there are fewer hydrogen atoms attached compared to a saturated hydrocarbon with the same number of carbon atoms.

In contrast, ethane, propane, and hexane are all saturated hydrocarbons. They contain only single bonds between carbon atoms, meaning they are fully "saturated" with hydrogen atoms. Each carbon atom in these compounds is bonded to the maximum number of hydrogen atoms possible, leading to a more stable structure. This distinction between saturated and unsaturated hydrocarbons is crucial in understanding the chemical properties and reactivity of these compounds, particularly in organic chemistry, where unsaturation can significantly influence chemical behavior.