Problem 212 - A Complete Resource Book in Chemistry for JEE Main

Question

The major organic compound formed by the reaction of \(1,1,1\)-trichloroethane with silver powder is: (a) 2-Butyne (b) 2-Butene (c) Acetylene (d) Ethene

Step-by-Step Solution

Answer

The major product is acetylene (option c).

Step 1: Understanding the Reagent

1,1,1-trichloroethane is a compound that reacts with silver powder, leading to a reaction known as dehalogenation. Silver acts as a dechlorinating agent, removing chlorine atoms from the compound.

Step 2: Consider the Reaction Mechanism

When 1,1,1-trichloroethane reacts with silver powder, the silver removes the chlorine atoms in pairs, facilitating the formation of a carbon-carbon triple bond. This is because silver facilitates the removal of halogen atoms.

Step 3: Predict the Product

By removing chlorine atoms and considering the remaining structure, the reaction yields a compound with a triple bond between two carbon atoms. This leads us to identify that the product formed would be acetylene, which is also known as ethyne.

Step 4: Choose the Correct Option

Reviewing the options given: (a) 2-butyne, (b) 2-butene, (c) acetylene, and (d) ethene, we can conclude that the major organic product formed is acetylene.

Key Concepts

Dehalogenation

Dehalogenation is a fundamental reaction in organic chemistry where halogen atoms are removed from a molecule. This process can significantly alter the chemical properties of the compound, making it more reactive or opening up new pathways for chemical transformations. In the exercise involving 1,1,1-trichloroethane, dehalogenation plays a crucial role as the chlorine atoms are stripped away from the molecule. This is achieved by using a dechlorinating agent, like silver, that aids in the removal of halogens. Understanding dehalogenation helps in predicting how molecules can be transformed, especially when aiming to form unsaturated or novel structures.

Acetylene formation

Acetylene, or ethyne, is a simple organic compound characterized by a carbon-carbon triple bond. During the exercise, we observed that the reaction of 1,1,1-trichloroethane with silver leads to this structure. The removal of three chlorine atoms enables the creation of this highly unsaturated compound. Acetylene is not just of theoretical interest; it has practical applications as well. It's used in welding torches and as a building block in the synthesis of various organic compounds. The process of forming acetylene in the discussed reaction exhibits the power of converting relatively simple starting materials into compounds with significant industrial and chemical relevance.

Reaction mechanism

The reaction mechanism is the step-by-step sequence of elementary reactions by which overall chemical change occurs. In the case of reacting 1,1,1-trichloroethane with silver, the mechanism involves the pairing and removal of chlorine atoms. This dehalogenation, carried out by silver, is facilitated by its ability to intercept halogen atoms and hold them away from the organic molecule. This step-by-step removal, and conversion sequence, ultimately forms a carbon-carbon triple bond. The triple bond is formed when enough halogen atoms are removed to allow the remaining carbon atoms to share three pairs of electrons. Understanding mechanisms is vital as it gives insight into the process, allowing chemists to modify and optimize conditions for reactions involving similar chemical transformations.

Silver as dechlorinating agent

Silver is an effective dechlorinating agent in organic chemistry due to its unique properties and reactivity. When silver is used in the reaction with 1,1,1-trichloroethane, it helps in efficiently removing chlorine atoms. Silver's positive atomic character allows it to interact with the negatively charged chlorine atoms, forming complexes that facilitate their removal. This interaction helps in replacing the halogen atoms on the organic molecule, often leading to the formation of more stable and desired organic structures such as the carbon-carbon triple bond seen in acetylene formation. The chemistry of silver is fascinating and important in conducting transformations necessary for both laboratory synthesis and industrial applications.