Alkynes are more reactive than alkanes and alkenes due to the presence of a triple bond between two carbon atoms. This triple bond consists of one sigma bond and two pi bonds. The pi bonds are weaker and more exposed than the sigma bond, making them more susceptible to attack by various reagents. This increased reactivity can be utilized in various organic synthesis reactions to form a wide range of products.One of the most common reactions that demonstrate the reactivity of alkynes is the addition reaction. In these reactions, the triple bond of the alkyne is partially or fully broken, and new atoms or groups are added to the carbon atoms. A specific example is the hydrohalogenation reaction, where a hydrogen halide HX, where X is a halogen is added to the alkyne.For example, let's consider the reaction of propyne CH3CCH with hydrogen bromide HBr :CH3CCH + HBr CH3C Br =CH2In this reaction, one of the pi bonds in the triple bond is broken, and the hydrogen atom from HBr is added to one carbon atom, while the bromine atom is added to the other carbon atom. The product is a brominated alkene, also known as 1-bromo-1-propene.This reaction can also be carried out with excess HBr to form a dibrominated alkane:CH3C Br =CH2 + HBr CH3C Br 2CH3In this second step, the remaining pi bond in the alkene is broken, and another hydrogen and bromine atom are added to the carbon atoms, resulting in a dibrominated alkane, also known as 1,1-dibromopropane.These reactions demonstrate the increased reactivity of alkynes compared to alkanes and alkenes, and their ability to undergo addition reactions to form various products in organic synthesis.