The dissociative photoionization of energy-selected cis-1-bromopropene, trans-1-bromopropene, 2-bromopropene, 3-bromopropene (allyl bromide) and bromocyclopropane was investigated by imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. Br loss was the only dissociation channel observed in the measured energy range. Cis-1-bromopropene, trans-1-bromopropene and 2-bromopropene cations are metastable at the 0K appearance energy of Br loss, whereas allyl bromide and bromocyclopropane cations dissociate quickly. The experimental onsets, supported by ab initio calculations, show that allyl bromide, cis- and trans-1-bromopropene, and bromocyclopropane dissociatively photoionize by Br loss to form the allyl cation, CH 2 CHCH 2 + . Due to the high barrier between the 2- and 3-bromopropene cations, the 2-bromopropene cation dissociates into the other, less stable C 3 H 5 + isomer, the 2-propenyl cation, CH 3 CCH 2 + . The 0K appearance energy of the allyl cation from the cis- and trans-1-bromopropenes, allyl bromide and bromocyclopropane was determined to be 10.581±0.014eV, 10.561±0.012eV, 10.522±0.005eV and 10.211±0.005eV, respectively. Similarly, the 0K appearance energy of the 2-propenyl cation from 2-bromopropene was determined to be 10.930±0.015eV. Using a mixed theoretical and experimental thermochemical network, the 0K heats of formation of cis-1-bromopropene, trans-2-bromopropene, allyl bromide, 2-bromopropene, and bromocyclopropane were determined as 64.7±2.9, 66.4±2.8, 70.3±2.6, 58.5±2.9, and 104.3±4kJmol −1 , respectively.