Help me write a chemical equation for the dehydration of cyclohexanol
The Correct Answer and Explanation is:
Balanced Chemical Equation:
C₆H₁₁OH → C₆H₁₀ + H₂O
(cyclohexanol → cyclohexene + water)
This reaction typically requires an acid catalyst like sulfuric acid (H₂SO₄) and heat:
C₆H₁₁OH → C₆H₁₀ + H₂O (in presence of H₂SO₄ and heat)
Explanation
The dehydration of cyclohexanol is a classic example of an elimination reaction (E1 mechanism) in organic chemistry. This reaction involves the removal of a water molecule (H₂O) from cyclohexanol to form an alkene, specifically cyclohexene.
The process begins with protonation of the hydroxyl group (-OH) by a strong acid such as sulfuric acid. This turns the hydroxyl into a better leaving group, forming a positively charged oxonium ion. The protonated -OH then leaves, producing a carbocation intermediate. In the case of cyclohexanol, the resulting carbocation is relatively stable because it is secondary and cyclic, helping the reaction proceed smoothly.
Once the carbocation is formed, a base (often the conjugate base of the acid, like HSO₄⁻) abstracts a proton (H⁺) from a carbon adjacent to the positively charged carbon. This leads to the formation of a double bond (C=C) and thus the creation of cyclohexene.
Heat is essential in this reaction because it helps drive the equilibrium toward product formation, favoring elimination over substitution. The overall reaction produces cyclohexene and water as products.
This reaction demonstrates acid-catalyzed dehydration, a method often used in the laboratory to produce alkenes from alcohols. The reaction is typically performed by heating cyclohexanol with concentrated sulfuric acid or phosphoric acid under reflux conditions, followed by distillation to isolate the alkene product.
In summary, the dehydration of cyclohexanol is a vital transformation in organic synthesis and is useful in understanding reaction mechanisms, intermediate stability, and the role of catalysts and temperature in chemical reactions.
