Rate constants for reactions of chlorine atoms with propene (k(1)) and 1-butene (k(2)) were measured relative to that of chlorine atoms with n-butane (k(3)) at 295-400 K in 5-900 Torr of N-2 using gas chromatographic analysis. Experiments were also performed using an FTIR smog chamber to measure k1 relative to cyclohexane (k(4)) at 290-302 K in 700 Torr of N-2. In contrast to previous studies which reported large negative activation energies, no discernable influence of temperature on the kinetics of these reactions was observed for experiments conducted near ambient temperature and pressure (vertical bar E-a(1)vertical bar <= 300 cal mole(1), vertical bar E-a(2) <= 6 150 cal mole (1)). (C) 2010 Elsevier B.V. All rights reserved.