Alicyclic Hydrocarbons

Abstract

Alicyclic hydrocarbons are ring structures comprised of three or more carbon molecules. Saturated molecules, those containing only single bonds, include cycloalkanes, also called cycloparaffins, cyclanes, and naphthenes. Unsaturated molecules, those containing one or more double bonds, include cycloalkenes, also called cycloolefins and cyclenes. Derivatives formed by alkyl or alkenyl substitution are widely known. Some compounds are isolated from crude petroleum refinery distillates or catalytically cracked petroleum products and used to produce reformed aromatics, as solvents or as synthesis intermediates. Naturally occurring derivatives found in plants are commonly called terpenes. Cyclopropane and cyclobutane are gases with anesthetic properties. Cyclopentane and higher members are liquids with low acute and chronic toxicity overall but may induce effects characteristic of lipophilic compounds, such as dose‐dependent central nervous system (CNS) depression, dizziness, and headache. Effects resolve readily when exposure stops. Following ingestion or inhalation, cycloalkanes are exhaled in unchanged form or rapidly metabolized into water‐soluble metabolites, usually glucuronides. Oral administration of high doses to animals resulted in severe diarrhea, vascular collapse, and heart, lung, liver, and brain degeneration. Some compounds cause ocular and/or dermal irritation, and skin defatting (dry skin). Some larger compounds are skin sensitizers, an effect increased with the number of double bonds present. Liquid members with low viscosity are aspiration hazards. Multiple compounds are associated with α 2 ‐u‐globulin‐induced nephrotoxicity in various strains of male rats, effects not considered biologically relevant in other species including human.