Kinetics and mechanism of the reactions of n‐butanal and n‐pentanal with chlorine atoms

The kinetics and mechanism of the reaction of chlorine atoms with n‐butanal and n‐pentanal have been investigated in a 142‐L reaction cell coupled to a Fourier transform infrared (FTIR) spectrometer at 298 ± 2 K and at 800 ± 3 Torr. The rate coefficients for Cl + n‐butanal and Cl + n‐pentanal were measured using the relative rate technique with isopropanol and ethene as the reference compounds. The yield of acyl radicals was determined by measuring yields of acid chloride and carbon monoxide products from the reaction of Cl + aldehyde in the absence of oxygen. The rate coefficients for Cl + n‐butanal and Cl + n‐pentanal are (1.63 ± 0.59) × 10^?10 cm³ molecule^?1 s^{? 1} and (2.37 ± 0.82) × 10^?10 cm³ molecule^?1 s^?1, respectively. The yields of acyl radicals from the reactions are 0.66 ± 0.04 for n‐butanal and 0.45 ± 0.04 for n‐pentanal. Under ambient conditions, the acyl radicals generated will react almost exclusively with oxygen. Mechanistic implications of these measurements are discussed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 133–141, 2009