The reaction of propyne CHCCH with hydrogen chloride HCl is an electrophilic addition reaction. The mechanism involves the following steps:1. Protonation of the alkyne: The hydrogen atom from HCl acts as an electrophile and attacks the electron-rich triple bond of propyne. The pi electrons from the triple bond form a bond with the hydrogen atom, creating a carbocation intermediate and leaving a chloride ion Cl in the solution. The carbocation intermediate has a double bond C=C and a positive charge on the carbon atom adjacent to the CH group.2. Nucleophilic attack by chloride ion: The chloride ion Cl , which is a nucleophile, attacks the positively charged carbon atom in the carbocation intermediate, forming a bond with it. This results in the formation of the final product.The product formed in this reaction is 1-chloro-2-propene CHC Cl =CH , also known as 1-chloropropene. This product is a haloalkene, which is formed by the addition of HCl across the triple bond of propyne.