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Figure 6:Reaction Coordinate Diagrams showing reactions with 0, 1 and 2 intermediates: The double-headed arrow shows the first, second and third step in each reaction coordinate diagram. In all three of these reactions the first step is the slow step because the activation energy from the reactants to the transition state is the highest.
Aromatization is a chemical reaction in which an aromatic system is formed from a single nonaromatic precursor. Typically aromatization is achieved by dehydrogenation of existing cyclic compounds, illustrated by the conversion of cyclohexane into benzene. Aromatization includes the formation of heterocyclic systems. [1]
This step is generally thought to proceed through a so-called β-hydride elimination with a cyclic four-membered transition state: Wacker hydride elimination. In silico studies [24] [25] [26] argue that the transition state for this reaction step is unfavorable and an alternative reductive elimination reaction mechanism is in play. The proposed ...
A side reaction is hydrogenolysis, which produces light hydrocarbons of lower value, such as methane, ethane, propane and butanes. Continuous Catalytic reforming (CCR) unit In addition to a gasoline blending stock, reformate is the main source of aromatic bulk chemicals such as benzene , toluene , xylene and ethylbenzene , which have diverse ...
The Buchner ring expansion is a two-step organic C-C bond forming reaction used to access 7-membered rings. The first step involves formation of a carbene from ethyl diazoacetate, which cyclopropanates an aromatic ring. The ring expansion occurs in the second step, with an electrocyclic reaction opening the cyclopropane ring to form the 7 ...
In chemistry, a reaction step of a chemical reaction is defined as: "An elementary reaction, constituting one of the stages of a stepwise reaction in which a reaction intermediate (or, for the first step, the reactants) is converted into the next reaction intermediate (or, for the last step, the products) in the sequence of intermediates between reactants and products". [1]
The reaction product is a derivative of benzene. Scheme 1. Bergman cyclization. The reaction proceeds by a thermal reaction or pyrolysis (above 200 °C) forming a short-lived and very reactive para-benzyne biradical species. It will react with any hydrogen donor such as 1,4-cyclohexadiene which converts to benzene.
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.