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Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula C 2 H 4 or H 2 C=CH 2. It is a colourless, flammable gas with a faint "sweet and musky " odour when pure. [ 7 ] It is the simplest alkene (a hydrocarbon with carbon–carbon double bonds ).
The equation of bromination of ethylene to form ethane is: H 2 C=CH 2 + Br 2 →H 2 CBr−CH 2 Br. Unlike hydrogenation, these halogenation reactions do not require catalysts. The reaction occurs in two steps, with a halonium ion as an intermediate. Structure of a bromonium ion. Bromine test is used to test the saturation of hydrocarbons. [17]
The chief use of ethane is the production of ethylene (ethene) by steam cracking. Steam cracking of ethane is fairly selective for ethylene, while the steam cracking of heavier hydrocarbons yields a product mixture poorer in ethylene and richer in heavier alkenes (olefins), such as propene (propylene) and butadiene, and in aromatic hydrocarbons.
The products produced in the reaction depend on the composition of the feed, the hydrocarbon-to-steam ratio, and on the cracking temperature and furnace residence time. Light hydrocarbon feeds such as ethane, LPGs, or light naphtha give mainly lighter alkenes, including ethylene, propylene, and butadiene.
Aromatic compounds, almost uniquely for hydrocarbons, undergo substitution reactions. The chemical process practiced on the largest scale is the reaction of benzene and ethene to give ethylbenzene: C 6 H 6 + C 2 H 4 → C 6 H 5 CH 2 CH 3
The products produced in the reaction depend on the composition of the feed, the hydrocarbon-to-steam ratio, and on the cracking temperature and furnace residence time. Light hydrocarbon feeds such as ethane, LPGs or light naphtha give product streams rich in the lighter alkenes, including ethylene, propylene, and butadiene.
The reaction is exothermic (∆H = -280 kJ/mol) and occurs at high temperatures (750–950 ˚C). [3] In the reaction, methane (CH 4) is activated heterogeneously on the catalyst surface, forming methyl free radicals, which then couple in the gas phase to form ethane (C 2 H 6). The ethane subsequently undergoes dehydrogenation to form ethylene ...
The reaction is an example of cross metathesis. The utility of the reaction is driven by the low cost of ethylene as a reagent and its selectivity. It produces compounds with terminal alkene functional groups (α-olefins), which are more amenable to other reactions such as polymerization and hydroformylation. The general reaction equation is: