Three moles of propyne gas are passed through a red-hot iron tube at 873 K to undergo cyclic polymer — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Mesitylene is a benzene ring substituted with three methyl groups ($C_6H_3(CH_3)_3$). Within the benzenoid ring, there are 6 $C-C$ $\sigma$ bonds and 3 $C-H$ $\sigma$ bonds. There are 3 $C-C$ $\sigma$ bonds connecting the methyl groups to the ring. Finally, each of the three methyl groups has 3 $C-H$ $\sigma$ bonds, totaling 9. The total number of $\sigma$ bonds = $6 + 3 + 3 + 9 = 21$.