Question

Ethene \(\frac{\mathrm{O}_{2}}{\mathrm{Ag} / \Delta} \mathrm{A}\) dil HCl/\Delta \(\mathrm{B}\). The product \(\mathrm{B}\) in the above reaction is (a) Ethanol (b) Ethane- 1,2 - diol (c) Ethanal (d) epoxyethane

Short answer

Answer: The final product B is Ethane-1,2-diol.

Step-by-step solution

Identify the initial molecule Ethene

Ethene is an unsaturated hydrocarbon that has a double bond between two carbon atoms. Ethene has a molecular formula of \(\mathrm{C}_2\mathrm{H}_4\).

React Ethene with Oxygen using Silver catalyst and heat

As given in the exercise, Ethene reacts with Oxygen (\(\mathrm{O}_2\)) in the presence of a Silver (Ag) catalyst and heat (\(\Delta\)). This reaction involves the addition of an oxygen atom across the double bond of Ethene. It forms an intermediate molecule known as epoxyethane or ethylene oxide: $$\mathrm{C}_2\mathrm{H}_4\ +\ \mathrm{O}_2 \xrightarrow[\Delta]{\mathrm{Ag}} \mathrm{C}_2\mathrm{H}_4\mathrm{O}$$

React the intermediate epoxyethane with dilute HCl and heat

In the next step, epoxyethane reacts with dilute HCl in the presence of heat (\(\Delta\)). In this reaction, a hydrochloric acid molecule (HCl) undergoes hydrolysis and forms product B. The reaction can be written as: $$\mathrm{C}_2\mathrm{H}_4\mathrm{O}\ +\ \mathrm{HCl} \xrightarrow[\Delta]{} \mathrm{B}$$

Identify the final product B

To determine the final product B, let's examine each of the given options: (a) Ethanol: \(\mathrm{C}_2\mathrm{H}_5\mathrm{OH}\) – Ethanol is formed by adding one hydrogen and one hydroxide (\(\mathrm{OH}\)) group to Ethene, which is not the case here. So, this option is incorrect. (b) Ethane-1,2-diol: \(\mathrm{C}_2\mathrm{H}_4(\mathrm{OH})_2\) – In this option, there are two hydroxide groups added to the molecule, which matches the addition of oxygen and HCl in our reactions. So, this is the correct option. (c) Ethanal: \(\mathrm{C}_2\mathrm{H}_4\mathrm{O}\) – This molecule is an aldehyde, which is not formed in the given reactions. So, this option is incorrect. (d) Epoxyethane: \(\mathrm{C}_2\mathrm{H}_4\mathrm{O}\) – This is the intermediate formed in the first step, not the final product B. So, this option is incorrect. Based on our analysis, the correct option is: **B) Ethane-1,2-diol**

Key concepts

Epoxyethane Formation

Epoxyethane, sometimes referred to as ethylene oxide, is an important intermediate in organic chemistry. Forming epoxyethane involves the reaction of ethene with oxygen. Ethene, with its molecular formula \( \mathrm{C}_2\mathrm{H}_4 \), is a simple unsaturated hydrocarbon having a carbon-carbon double bond. This double bond makes ethene highly reactive, especially useful for forming new compounds.

The transformation takes place in the presence of a silver catalyst and heat. The catalyst, silver, helps facilitate the addition of oxygen to the reactive double bond of ethene. This results in the formation of a cyclic ether known as epoxyethane. The reaction can be summarized as:
\[ \mathrm{C}_2\mathrm{H}_4 + \mathrm{O}_2 \xrightarrow[\Delta]{\mathrm{Ag}} \mathrm{C}_2\mathrm{H}_4\mathrm{O} \]

This synthesis is crucial in industries for producing further derivatives of ethylene oxide, which are extensively used in making antifreeze, detergents, and other chemicals.

Ethene Reactions

Ethene reactions form the basis for many industrial chemical processes. The fundamental aspect of ethene is its carbon-carbon double bond, which acts as a site for various addition reactions.

In the context of the exercise, ethene undergoes an oxidation reaction to form epoxyethane by reacting with oxygen. This is just one pathway. Ethene can also participate in other reactions:

• Halogenation: Adds halogens (like Br or Cl) to break the double bond.
• Hydration: Converts ethene to ethanol by adding water.
• Hydrohalogenation: Forms haloalkanes by adding hydrogen halides.

Understanding these reactions allows chemists to derive a multitude of products from ethene, catering to diverse industrial needs.

Hydrolysis with HCl

Hydrolysis is a reaction involving the splitting of a compound by water. In this scenario, epoxyethane undergoes hydrolysis with dilute hydrochloric acid (HCl) in the presence of heat.

This process transforms the epoxyethane into ethane-1,2-diol. Here's why: The acidic environment provided by hydrochloric acid facilitates the opening of the epoxide ring. Water is added during this process, leading to the formation of two hydroxyl groups, resulting in a diol. The reaction can be depicted as:
\[ \mathrm{C}_2\mathrm{H}_4\mathrm{O} + \mathrm{HCl} \xrightarrow[\Delta]{} \mathrm{C}_2\mathrm{H}_4(\mathrm{OH})_2 \]

Hydrolysis reactions like these are valuable in converting reactive intermediates into stable and useful alcohols such as diols, which are vital in manufacturing antifreeze solutions and polymer industries.