Cannizzaro’s (C7H6) n conundrum resolved: [1.1.1]orthocyclophane was first made 150 years ago

The product of the reaction of benzyl alcohol with a number of Lewis acids was shown by Cannizzaro in 1854 to have the empirical formula (C7H6) n , and this material has been the subject of much controversy for many decades. Its attribution as an isomer of 1,2,3,4,5,6-hexaphenylcyclohexane is shown to be incorrect, and instead it has been identified as 10,15-dihydro-5H-tribenzo[a,d,g]cyclononene, 3, the parent [1.1.1]orthocyclophane, the X-ray crystal structure of which is reported.