To bond or not to bond – What if the temperature is the question?

Bond formation in 1,8-dimethylenenaphthalene neutrals and cations (C 12 H 10 (+•) , 154 amu) was probed with mass spectrometry, pyrolysis/photoelectron photoion coincidence spectroscopy (py-PEPICO) and theory. The mass-analyzed ion kinetic energy (MIKE) spectra and neutralization–reionization (NR) mass spectra obtained for m / z 154 from directly ionized acenaphthene ( 1 ) and dissociatively ionized 1,8-bis(bromomethyl) naphthalene (C 12 H 10 Br 2 , 1,8-BM) were distinguishable. Combined with theory, the results were interpreted as the two sources forming 1 +• ions with different average internal energy contents. Pyrolytic debromination of 1,8-BM was found to produce both acenaphthene 1 and acenaphthylene. • 1,8-Bis(bromomethyl)naphthalene undergoes dissociative EI to form high energy acenaphthene ions ( m / z 154). • Neutralization of the m/z 154 ions from 1,8-bis(bromomethyl)naphthalene leads to high energy neutrals that dissociate. • Pyrolysis of 1,8-bis(bromomethyl)naphthalene forms both acenaphthene and acenaphthylene.