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Steam cracker process diagram Gibbs free energy per carbon atom. This shows that at high temperature, hexane can split into ethane and ethylene ("Ethen"), and ethane can split into ethylene and hydrogen. But ethylene can decompose into methane and carbon if given too much time, and all the hydrocarbons can decompose into carbon and hydrogen.
An overall process of disproportionation can be observed, where "light", hydrogen-rich products are formed at the expense of heavier molecules which condense and are depleted of hydrogen. The actual reaction is known as homolytic fission and produces alkenes , which are the basis for the economically important production of polymers .
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).
In this reaction a variety of reagents add "across" the pi-bond(s). Chlorine, hydrogen chloride, water, and hydrogen are illustrative reagents. Polymerization is a form of addition. Alkenes and some alkynes also undergo polymerization by opening of the multiple bonds to produce polyethylene, polybutylene, and polystyrene.
Hydration is an important process in many other applications; one example is the production of Portland cement by the crosslinking of calcium oxides and silicates that is induced by water. Hydration is the process by which desiccants function. CuSO 4 ·5H 2 O is bright blue and has a rather different structure from its colourless anhydrous ...
In an ethene monomer, one electron pair is held securely between the two carbons in a sigma bond. The other is more loosely held in a pi bond. The free radical uses one electron from the pi bond to form a more stable bond with the carbon atom. The other electron returns to the second carbon atom, turning the whole molecule into another radical.
Another key step in the Wacker process is the migration of the hydrogen from oxygen to chloride and formation of the C-O double bond. 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 the first step, borane (BH 3) adds to the double bond, transferring one of the hydrogen atoms to the carbon adjacent to the one that becomes bonded to the boron. This hydroboration is repeated two additional times, successively reacting each B–H bond so that three alkenes add to each BH 3. The resulting trialkylborane is treated with ...