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Alkenes can be made from alcohols by dehydration. This conversion, among others, is used in converting biomass to liquid fuels. [2] The conversion of ethanol to ethylene is a fundamental example: [3] [4] CH 3 CH 2 OH → H 2 C=CH 2 + H 2 O. The reaction is accelerated by acid catalysts such as sulfuric acid and certain zeolites.
Professor David Todd at Pomona College was testing the dehydration of 2-methylcyclohexanol or 4-methylcyclohexanol c. 1994 and unexpectedly interrupted the alkene distillation midway to have lunch with his secretary, Evelyn Jacoby. After lunch, he continued his distillation but kept the early products separate from the completed ones.
In organic chemistry, an alkene, or olefin, ... Two common methods of elimination reactions are dehydrohalogenation of alkyl halides and dehydration of alcohols.
The one-pot dehydration of a primary alcohol to give an alkene through an o-nitrophenyl selenoxide intermediate is called the Grieco elimination. [19] [20] The reaction begins with the formation of a selenophosphonium salt which reacts with the alcohol to form an oxaphosphonium salt.
The Burgess reagent is used to convert secondary and tertiary alcohols with an adjacent proton into alkenes. Dehydration of primary alcohols does not work well. The reagent is soluble in common organic solvents and alcohol dehydration takes place with syn elimination through an intramolecular elimination reaction.
Alkenes are precursors to aldehydes (R−CH=O), alcohols (R−OH), polymers, and aromatics. [1] As a problematic reaction, the fouling and inactivation of many catalysts arises via coking, which is the dehydrogenative polymerization of organic substrates. [2] Enzymes that catalyze dehydrogenation are called dehydrogenases.
The reaction, in general, obeys Zaitsev's Rule, which states that the most stable (usually the most substituted) alkene is formed. Tertiary alcohols are eliminated easily at just above room temperature, but primary alcohols require a higher temperature. This is a diagram of acid catalyzed dehydration of ethanol to produce ethylene:
The general chemical equation for the hydration of alkenes is the following: RRC=CH 2 + H 2 O → RRC(OH)-CH 3. A hydroxyl group (OH −) attaches to one carbon of the double bond, and a proton (H +) adds to the other. The reaction is highly exothermic. In the first step, the alkene acts as a nucleophile and attacks the proton, following ...