2-Methyl-1,5-hexadiene on mercury-photosensitized irradiation, undergoes internal cycloaddition to afford 1-methylbicyclo[2. 1. 1]hexane (as major product). High-temperature pyrolysis of 2-methyl-1,5-hexadiene affords 1,5-hexadiene and 2,5-dimethyl-1,5-hexadiene. 2-Methyl-1,5-hexadiene undergoes stereoselective and regioselective reaction with dialkylaluminum chloride (Et2AlCl) and titanium alkoxide [Ti(OPr-i)4, a catalyst] followed by oxidation to afford the corresponding five-membered 3-alkylcycloalkyl methanol. 2-Methyl-1,5-hexadiene is formed as a major product during the condensation reaction between allyl chloride and methallyl chloride in the presence of magnesium.