Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Catalyzed Dehydration
Acid-catalyzed dehydration of alcohols involves the removal of a water molecule to form an alkene. This reaction is reversible because the products (alkene and water) can react under certain conditions to regenerate the starting alcohol. The equilibrium established between the reactants and products allows for both forward and reverse reactions, influenced by factors like temperature and concentration.
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General features of acid-catalyzed dehydration.
Base-Promoted Dehydrohalogenation
Base-promoted dehydrohalogenation is a reaction where a base removes a hydrogen halide (HX) from an alkyl halide, resulting in the formation of an alkene. This reaction is typically irreversible due to the strong bond formation in the alkene product and the stability of the leaving group (halide ion). The reaction proceeds to completion, as the formation of the alkene is favored energetically, making the reverse reaction less likely.
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Reaction Equilibrium
Reaction equilibrium refers to the state in which the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. In reversible reactions, such as acid-catalyzed dehydration, changes in conditions can shift the equilibrium position. In contrast, irreversible reactions, like base-promoted dehydrohalogenation, favor the formation of products to such an extent that the reverse reaction is negligible, leading to a one-way process.
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Determining Acid/Base Equilibrium