dehydrogenated

Dehydrogenated is an adjective referring to a molecule that has had one or more hydrogen atoms removed. In practice, dehydrogenation is the chemical process that removes hydrogen from a substrate and is the reverse of hydrogenation. Dehydrogenated species often contain increased unsaturation, such as additional double bonds, and may release hydrogen gas (H2) as a byproduct.

Mechanism and conditions: The process is generally endothermic and requires energy input. Industrial dehydrogenations rely on high temperatures and catalysts to achieve practical rates and selectivity. Common catalysts include transition metals such as platinum, palladium, and nickel, or oxide-based systems like chromium oxide or vanadium oxide supported on carriers. Reaction conditions are chosen to balance conversion, selectivity, and resistance to side reactions such as cracking or coking.

Representative reactions: Ethane dehydrogenation to ethene: C2H6 → C2H4 + H2. Ethylbenzene dehydrogenation to styrene: C6H5–CH2–CH3 → C6H5–CH=CH2 + H2. Ethanol dehydrogenation to acetaldehyde: C2H5OH → CH3CHO + H2. Cyclohexane dehydrogenation to benzene: C6H12 → C6H6 + 3 H2. These examples illustrate how hydrogen removal can generate alkenes, aromatics, or carbonyl compounds, often with hydrogen gas as a byproduct.

Applications and considerations: Dehydrogenation is a key step in producing industrial feedstocks such as alkenes (ethylene, propylene) and aromatics, as well as in some fuel-processing and synthetic pathways. The term dehydrogenated may also describe materials that have undergone hydrogen loss, affecting properties like stability and conductivity in polymers or carbon-based materials.