Formation and reactions of alkyl adamantanes in sediments: Carbon surface reactions

► Alkyl adamantanes formed via sealed tube heating of β-ionone with activated carbon. ► The mild conditions suggest such reactions could occur in sediments in the oil generation zone. ► Alkyl adamantanes also undergo demethylation, methyl transfer, isomerisation and hydrogen exchange on carbonaceous surfaces. ► First report of formation and rearrangement of alkyl adamantanes via carbon surface reactions. ► Evidence for acid-catalysed carbocation rearrangements not being the exclusive pathway to diamondoid formation.