What is formed when ethyl tetrahalide undergoes dehalogenation?

When ethyl tetrahalide (C₂H₂X₄) undergoes dehalogenation, the product formed is ethyne (C₂H₂), also known as acetylene. Dehalogenation is a type of elimination reaction in organic chemistry where halogen atoms are removed from a molecule, often in the presence of a reducing agent such as zinc (Zn) or sodium (Na) in alcoholic medium.

In this reaction, two molecules of a halogen atom are removed from adjacent carbon atoms, leading to the formation of a carbon–carbon triple bond. The overall process converts a saturated tetrahalide into an unsaturated alkyne. The general reaction can be represented as:

C₂H₂X₄ + 2Zn → C₂H₂ + 2ZnX₂

Here, zinc acts as the reducing agent, facilitating the removal of halogen atoms as zinc halide (ZnX₂). The resulting compound, ethyne, is the simplest alkyne, containing a triple bond between the two carbon atoms.

This reaction is one of the classical laboratory methods for preparing alkynes from tetrahalides. The type of halogen (Cl, Br, or I) affects the reaction rate, with diiodides reacting most readily due to weaker carbon–iodine bonds.

Ethene (C₂H₄) is formed through dehydrohalogenation, while ethyne (C₂H₂) results specifically from dehalogenation of tetrahalides. The difference lies in the number of halogen atoms removed and the type of bond formed in the product.

Thus, the dehalogenation of ethyl tetrahalide gives ethyne as the main product, demonstrating the conversion of a halogenated hydrocarbon into a simple alkyne through elimination and reduction reactions.