Replacement of a hydrogen atom in a hydrocarbon by an alkoxy or carboxyl group yields a class of compounds known as ethers. Ethers are classified as symmetrical or unsymmetrical on the basis of groups attached to the oxygen atoms. Diethyl ether, a symmetrical ether, has been widely used as an inhalation anesthetic. Ethers can be prepared by acid catalyzed intermolecular dehydration of alcohols and Williamson's synthesis. Acid catalyzed dehydration of alcohols is not generally preferred as it gives a mixture of elimination and substitution products. In Williamson's synthesis, an alkyl halide is allowed to react with sodium alkoxide. Ethers containing substituted Alkyl groups may also be prepared by this method. The C-O bond in ether is weakly polar and is cleaved under drastic conditions with excess of hydrogen halides. In electrophilic substitution, the alkoxy group deactivates the aromatic ring and directs the incoming group to ortho and para positions.
Dehydration of Ethanol Reaction Products
The question asks about the products formed when ethanol is dehydrated using sulfuric acid ($H_2SO_4$) at two different temperatures: 443K and 413K.
Understanding Alcohol Dehydration with Sulfuric Acid
The dehydration of alcohols using concentrated sulfuric acid ($H_2SO_4$) is a common reaction in organic chemistry. The process involves the removal of a water molecule from the alcohol. Sulfuric acid acts as a catalyst and a dehydrating agent. The outcome of the reaction, specifically whether an alkene (like ethene) or an ether (like diethyl ether) is formed, strongly depends on the reaction temperature.
The provided text mentions that "Acid catalyzed dehydration of alcohols is not generally preferred as it gives a mixture of elimination and substitution products." This indicates that both types of reactions are possible under acidic conditions.
Reaction Pathways at Specific Temperatures
Based on standard chemical principles and the information implied by the options, the temperature plays a crucial role:
Reaction at 443K
When ethanol ($C_2H_5OH$) is heated with concentrated sulfuric acid ($H_2SO_4$) at approximately 443K, the reaction predominantly follows an elimination pathway. In this process, a molecule of water is eliminated from ethanol, leading to the formation of ethene ($C_2H_4$), which is an unsaturated hydrocarbon (an alkene), and water ($H_2O$).
The chemical equation for this reaction is:
$C_2H_5OH \xrightarrow{H_2SO_4, 443K} C_2H_4 \uparrow + H_2O$
Here, $C_2H_4$ represents ethene.
Reaction at 413K
When ethanol ($C_2H_5OH$) is heated with concentrated sulfuric acid ($H_2SO_4$) at a slightly lower temperature, approximately 413K, the reaction primarily follows an intermolecular dehydration pathway. This means two molecules of ethanol react together. One molecule loses a hydroxyl group ($-OH$) and the other loses a hydrogen atom ($H$), forming a water molecule ($H_2O$) and linking the remaining ethyl groups ($C_2H_5-$) through an oxygen atom. This results in the formation of diethyl ether ($C_2H_5OC_2H_5$), also known as ethoxyethane, which is a type of ether.
The chemical equation for this reaction is:
$2 C_2H_5OH \xrightarrow{H_2SO_4, 413K} C_2H_5OC_2H_5 + H_2O$
Here, $C_2H_5OC_2H_5$ represents ethoxyethane (diethyl ether).
Product Identification Summary
The question specifies that the temperatures are 443K and 413K "respectively". This means the first product corresponds to 443K and the second product corresponds to 413K.
- At 443K: Ethene ($C_2H_4$) is formed.
- At 413K: Ethoxyethane ($C_2H_5OC_2H_5$) is formed.
Conclusion
Therefore, when ethanol is dehydrated in the presence of $H_2SO_4$ at 443K and 413K respectively, the products formed are Ethene and Ethoxyethane.
Important Questions from Alcohols, Phenols And Ethers
Among the following statements, choose the correct statements.
A. Boiling point of alcohols increases with increase in the number of carbon atoms.
B. In alcohols, boiling points increases with increase of branching in carbon chain.
C. Boiling points of alcohols are lesser in comparison to haloalkanes of comparable molecular mass.
D. Boiling points of alcohols are higher in comparison to hydrocarbons of comparable molecular mass.
E. The high boiling points of alcohols are mainly due to the presence of intramolecular hydrogen bonding.
Choose the correct answer from the options given below:
Which of the following compounds is most acidic in character?
Isomer of diethyl ether is
What is aspirin?
The reactivity of primary, secondary and tertiary hydrogen for bromination is ____________.
