carbonohidrogênio

Carbonohidrogênio, in chemical terminology often referred to simply as hydrocarbons, denotes organic compounds composed exclusively of carbon and hydrogen. They are among the most abundant organic substances on Earth and form the basis of many fuels and chemical feedstocks. Hydrocarbons occur naturally in fossil fuels such as crude oil and natural gas, as well as in some plants and soils.

Classification usually distinguishes aliphatic hydrocarbons (open-chain and cyclic) from aromatic hydrocarbons. Aliphatic hydrocarbons include saturated alkanes (single bonds), and unsaturated alkanes such as alkenes (double bonds) and alkynes (triple bonds). Cyclic aliphatic hydrocarbons include cycloalkanes. Aromatic hydrocarbons contain one or more stable ring systems, most notably benzene and its derivatives, with characteristic ring stability and delocalized electrons.

Physical and chemical properties depend on structure. Hydrocarbons are largely nonpolar and exhibit little solubility in water but high solubility in nonpolar solvents. With increasing carbon number, boiling and melting points rise. They are typically flammable and release energy when combusted. Alkanes are relatively unreactive, while alkenes, alkynes, and aromatics undergo characteristic addition or substitution reactions.

Occurrences and applications: hydrocarbons are major constituents of petroleum and natural gas and serve as fuels (gasoline, diesel, jet fuel) and as feedstocks for plastics, solvents, lubricants, and many chemicals. Refined products and petrochemical processes convert simple hydrocarbons into a wide range of materials and energy carriers.

Safety and environmental notes: vapors are often flammable and can form explosive mixtures with air. Some hydrocarbons are toxic or carcinogenic, particularly certain aromatic compounds. Combustion releases carbon dioxide and other pollutants, contributing to air quality and climate concerns.