The compound formed when alcoholic solution of ethylene dibromide is heated with granulated zinc is (a) ethene (b) ethyne (c) ethane (d) bromoethane.

Ethylene dibromide, also known as 1,2-dibromoethane, is a colorless, heavy organic compound that is liquid at room temperature. It is a member of the haloalkanes, a group of compounds in which one or more halogen atoms are connected to carbon atoms within a chain or ring structure. In organic synthesis, ethylene dibromide is significant because it's often used as an intermediate in the manufacture of other chemicals and as a starting material for dehalogenation reactions. Dehalogenation of ethylene dibromide under certain conditions, such as the presence of a reducing agent like zinc, leads to the formation of alkenes. This reaction showcases the versatility and reactivity of haloalkanes and their utility in producing more complex organic molecules.
The dehalogenation process is a valuable reaction in organic chemistry because it provides a pathway to remove halogens from organic compounds. This is particularly useful when synthesizing unsaturated hydrocarbons, such as alkenes, from saturated haloalkanes.

Zinc is a metallic element that has powerful reducing properties, making it a valuable agent in numerous chemical reactions. As a reducing agent, zinc donates electrons to other substances during a chemical reaction. This electron donation is what facilitates the transformation of molecules. When used in the context of organic chemistry reactions, zinc can effectively remove halogen atoms from organic compounds like ethylene dibromide. In its granulated form, zinc provides a large surface area for the reaction to take place, ensuring that the process happens efficiently.
Zinc's role in dehalogenation reactions is pivotal as it leads to the formation of alkenes by breaking the carbon-halogen bonds within haloalkanes. In the case of ethylene dibromide, zinc removes the bromide ions, leaving behind a double bond between the carbon atoms, which forms the alkene.

Alkenes are hydrocarbons containing at least one carbon-carbon double bond and are characterized by the suffix '-ene.' These unsaturated compounds are crucial in various chemical industries and serve as key intermediates for polymers, alcohols, and other organic compounds. The formation of alkenes can occur through dehalogenation reactions, where halogen atoms are removed from alkyl halides. Ethylene dibromide, when treated with a reducing agent like zinc, undergoes such a transformation.

Reaction Mechanism

During this process, the electrons from zinc reduce the carbon-halogen bonds, effectively removing the halogen atoms as halide ions. The loss of these atoms allows the remaining carbon atoms to form a double bond, resulting in an alkene. Ethene is the simplest alkene and is produced through the dehalogenation of ethylene dibromide.

Organic chemistry is the branch of science that deals with the structure, properties, and reactions of organic molecules containing carbon. Reactions in organic chemistry are numerous and varied, with dehalogenation being just one example. This field is fundamental to the development of pharmaceuticals, plastics, fuels, and countless other materials that are essential to modern life.
Understanding the various types of reactions, such as addition, substitution, elimination, and rearrangement reactions, allows chemists to synthesize complex molecules and manipulate molecular structures. In educational contexts, grasping these reaction mechanisms is crucial for students to excel in organic chemistry studies. Each reaction type has unique conditions and catalysts, like zinc's role in dehalogenation, which can lead to specific products such as the formation of alkenes from haloalkanes.