Ring opening fragmentations of ionized cyclohexylamines

Fragmentations of cyclohexylamine and dicyclohexylamine ions were studied using FTMS. Fragmentations of the molecular ions were initiated by the ring opening of cyclohexyl group to form the distonic molecular ions. The structures of fragment ions were determined by rearranging the distonic molecular ion. The major fragment ions were found to be XHCNH2+ and c-C6H11HNCHX+ for cyclohexylamine and dicyclohexylamine, respectively, where X is CHCH2 and CH2CHCH2. The formations of CH2CHCHNH2+ and c-C6H11HNCHCHCH2+ for cyclohexylamine and dicyclohexylamine, respectively, were more favorable than the formations of the other fragment ions because of the easy rearrangement of the distonic molecular ions. Experimental and calculation results suggest that the formations of fragment ions with acyclic structures were more favorable than those with cyclic ones. It was also found that for dicyclohexylamine the formations of fragment ions with cyclohexyl group, such as c-C6H11HNCHX+ were more favorable than those without cyclohexyl group, such as XHCNH2+.