What distinguishes aliphatic hydrocarbons?

Aliphatic hydrocarbons are characterized by their nonpolar nature, which means they do not have a significant charge separation within the molecules. This nonpolarity arises because aliphatic hydrocarbons consist primarily of carbon and hydrogen atoms arranged in linear or branched chains, lacking the polar functional groups that would contribute to charge separation. Due to their nonpolar nature, aliphatic hydrocarbons have low solubility in water but are soluble in organic solvents, which further underlines their chemical behavior and reactions, including their reactivity and interactions with other substances.

The presence of a benzene ring would indicate that a hydrocarbon is aromatic rather than aliphatic. A cyclical ring molecular structure typically refers to compounds that are not strictly aliphatic, as it usually implies the presence of cyclic compounds. Highly toxic properties can vary widely among different hydrocarbons but are not a defining characteristic of aliphatic hydrocarbons as a group. Therefore, the defining aspect of aliphatic hydrocarbons is their nonpolar nature.