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The Buchner ring expansion reaction was first used in 1885 by Eduard Buchner and Theodor Curtius [1] [2] who prepared a carbene from ethyl diazoacetate for addition to benzene using both thermal and photochemical pathways in the synthesis of cycloheptatriene derivatives.
The term stems from cumene (isopropyl benzene), the intermediate material during the process. It was invented by R. Ūdris and P. Sergeyev in 1942 (USSR), [1] and independently by Heinrich Hock in 1944. [2] [3] This process converts two relatively cheap starting materials, benzene and propylene, into two more valuable ones, phenol and acetone.
Benzene can be easily converted to chlorobenzene by nucleophilic aromatic substitution via a benzyne intermediate. [1] It is treated with aqueous sodium hydroxide at 350 °C and 300 bar or molten sodium hydroxide at 350 °C to convert it to sodium phenoxide, which yields phenol upon acidification. [2]
The Raschig–Hooker process's ability to make phenol makes it comparable to other methods, such as the Dow and Bayer process, which also converts benzene into phenol. In fact, the ability to recycle the hydrogen chloride made the Raschig–Hooker process preferable to the Dow and Bayer process, which requires its sodium chloride product to be ...
This is accomplished by the Gattermann-Koch reaction, accomplished by treating benzene with carbon monoxide and hydrogen chloride under high pressure, catalyzed by a mixture of aluminium chloride and cuprous chloride. Simple ketones that could be obtained by Friedel–Crafts acylation are produced by alternative methods, e.g., oxidation, in ...
This contributes both to costs and the emissions of the process. Catalytic reforming has a limited ability to process naphthas with a high content of normal paraffins, e.g. naphthas from the gas-to-liquids (GTL) units. The reformate has a much higher content of benzene than is permissible by the current regulations in many countries.
Most of those methods, but not all, involve the use of a solvent either for liquid-liquid extraction or extractive distillation. Many different solvents are suitable, including sulfolane (C 4 H 8 O 2 S), furfural (C 5 H 4 O 2 ), tetraethylene glycol (C 8 H 18 O 5 ), dimethylsulfoxide (C 2 H 6 OS), and N-methyl-2-pyrrolidone (C 5 H 9 NO).
European petrol specifications now contain the same 1% limit on benzene content. The United States Environmental Protection Agency introduced new regulations in 2011 that lowered the benzene content in gasoline to 0.62%. [71] In some European languages, the word for petroleum or gasoline is an exact cognate of "benzene".