2-Chloropropene and 2-bromopropene have been decomposed in single pulse shock tube experiments. The only products under all conditions are propyne and allene. The high pressure rate expressions are k(2-BrC₃H₅ ⇒ propyne/allene + HBr) = 10^14.9exp(−32 830/RT) s⁻¹k(2-ClC₃H₅ ⇒ propyne/allene + HCl) = 10^14.8exp(−34 200/RT) s⁻¹ in the temperature range 1100 to 1250 K and pressures of 150 to 800 kPa. The propyne to allene ratios are 1.8 and 1.6 for the brominated and chlorinated compounds respectively with minimal temperature dependence. Results are compared with those for the alkyl compounds and ab-initio calculations on 2-chloropropene. Differences in energy transfer efficiencies for 2-chloropropene and 4-methylcyclohexene decompositions are explored.