Associate Safety Professional Practice Exam

Which group of hydrocarbons is least likely to be flammable?

1. Aromatic hydrocarbons

2. Aliphatic hydrocarbons

3. Halogenated hydrocarbons

4. Cyclic hydrocarbons

The correct answer is: Halogenated hydrocarbons

Halogenated hydrocarbons are least likely to be flammable due to the presence of halogen atoms, such as chlorine, fluorine, bromine, or iodine, in their molecular structure. These halogens are highly electronegative and can disrupt the combustion process that is necessary for flammability. In general, the presence of halogens tends to stabilize the hydrocarbon, making it less reactive and less likely to ignite compared to other classes of hydrocarbons. In contrast, aromatic, aliphatic, and cyclic hydrocarbons typically have structures that allow for easy combustion. Aromatic hydrocarbons, with their stable ring structures, can still participate in combustion reactions. Aliphatic hydrocarbons, which include both saturated and unsaturated types, often readily vaporize and mix with air, leading to flammability. Cyclic hydrocarbons also have the potential to combust easily, though their reactivity can vary based on the specific compounds. Therefore, halogenated hydrocarbons stand out in this context as the least flammable group due to their chemical properties that inhibit combustion.