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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. These reactions often proceed via carbocation intermediates as shown for the dehydration of cyclohexanol. [5] Some alcohols are prone to dehydration.
The reaction may otherwise involve the functional groups of the molecule, and is a versatile class of reactions that can occur in acidic or basic conditions or in the presence of a catalyst. This class of reactions is a vital part of life as it is essential to the formation of peptide bonds between amino acids and to the biosynthesis of fatty ...
The Evelyn effect is defined as the phenomena in which the product ratios in a chemical reaction change as the reaction proceeds. This phenomenon contradicts the fundamental principle in organic chemistry by reactions always go by the lowest energy pathway. The favored product should remain so throughout a reaction run at constant conditions.
Another useful example is the one pot two-step synthesis of halfordinol, a parent compound for Rutaceae alkaloids. The initial steps follow the Fischer oxazole synthesis, although the acid-catalyzed cyclization occurs in two steps rather than one, which ensures the formation of the di-chloro intermediate , preventing formation of the regioisomer .
An aldol condensation is a condensation reaction in organic chemistry in which two carbonyl moieties (of aldehydes or ketones) react to form a β-hydroxyaldehyde or β-hydroxyketone (an aldol reaction), and this is then followed by dehydration to give a conjugated enone. The overall reaction equation is as follows (where the Rs can be H)
In a variation the reaction of phenols and beta-ketoesters and phosphorus pentoxide yields a chromone.This reaction is called Simonis chromone cyclization. [6] [7] The ketone in the ketoester is activated by P 2 O 5 for reaction with the phenol hydroxyl group first, the ester group in it is then activated for electrophilic attack of the arene.
The Robinson–Gabriel synthesis is an organic reaction in which a 2-acylamino-ketone reacts intramolecularly followed by a dehydration to give an oxazole.A cyclodehydrating agent is needed to catalyze the reaction [1] [2] [3] It is named after Sir Robert Robinson and Siegmund Gabriel who described the reaction in 1909 and 1910, respectively.
Because of the removal of the water molecule from the product, the term of convenience for such a process is "dehydration reaction" (also "condensation reaction" or "dehydration synthesis"). For example, milk sugar (lactose) is a disaccharide made by condensation of one molecule of each of the monosaccharides glucose and galactose, whereas the ...