Physical Properties of Alkynes

Alkynes are unsaturated hydrocarbons that have at least one triple bond between two carbon atoms. In this sub-lesson, we will be discussing the physical properties of alkynes, including their melting and boiling points, solubility, and acidity.

Melting and Boiling Points

Alkynes have higher melting and boiling points compared to alkanes and alkenes due to the presence of the triple bond. The triple bond is a strong bond that requires more energy to break, resulting in higher melting and boiling points. As the number of carbons in the alkyne chain increases, the melting and boiling points also increase.

Solubility

Alkynes are generally insoluble in water due to their nonpolar nature. However, they are soluble in nonpolar solvents such as benzene, toluene, and chloroform. The solubility of alkynes decreases as the size of the alkyne chain increases.

Acidity

Alkynes are weakly acidic due to the presence of the sp hybridized carbon in the triple bond. The acidity of alkynes is lower than that of alcohols and carboxylic acids but higher than that of alkanes and alkenes. The acidity of alkynes increases as the number of alkyl groups attached to the triple bond decreases.

Summary

In this lesson, we learned about the physical properties of alkynes. Alkynes have higher melting and boiling points compared to alkanes and alkenes due to the presence of the triple bond. They are generally insoluble in water but soluble in nonpolar solvents. Alkynes are weakly acidic due to the presence of the sp hybridized carbon in the triple bond.

Test Your Knowledge:

Why do alkynes have higher melting and boiling points compared to alkanes and alkenes?

How does the solubility of alkynes change as the size of the alkyne chain increases?