R. A. Perry

Rate constants for the reaction of OH radicals with COS, CS2 and CH3SCH3 over the temperature range 299–430 K

Abstract Rate constants for the reaction of OH radicals with COS, CS 2 and CH 3 SCH 3 , which are involved in the global sulfur cycle, have been determined over the temperature range 299–430 K using a flash photolysis-resonance fluorescence technique. For COs and CS 2 upper limits at room temperature of k (COS) −15 cm 3 molecule −1 s −1 and k (CS 2 ) −14 cm 3 molecule −1 s −1 were determined, while for CH 3 SCH 3 the Arrhenius expression k (CH 3 SCH 3 ) = 5.47 × 10 −12 exp[(355 ± 300)/ RT ] cm 3 molecule −1 s −1 was obtained with a rate constant at room temperature of (9.8 ± 1.2) × 10 −12 cm 3 molecule −1 s −1 .

Rate constants for the reaction of the OH radical with CH3SH and CH3NH2 over the temperature range 299–426 °K

Rate constants for reaction of the OH radical with CH3SH and CH3NH2 were determined over the temperature range 299–426 °K by a flash photolysis–resonance fluorescence technique. The Arrhenius expressions obtained were k (CH3SH) =8.89×10−12e(790±300)/RT cm3 molecule−1 sec−1 and k (CH3NH2) =1.02×10−11e(455±300)/RT cm3 molecule−1 sec−1, with rate constants at room temperature of (3.39±0.34) ×10−11 and (2.20±0.22) ×10−11 cm3 molecule−1 sec−1 for CH3SH and CH3NH2, respectively.

Rate constants for the reactions OH+H2S→H2O+SH and OH+NH3 →H2O+NH2 over the temperature range 297–427 °K

Rate constants for the reactions OH+H2S→H2O+SH (k1) and OH+NH3→H2O+NH2 (k2) were determined over the temperature range 297–427 °K by a flash photolysis–resonance fluorescence technique. The Arrhenius expressions obtained were k1= (5.2±0.5) ×10−12 cm3 molecule−1sec−1, independent of temperature (297–424 °K); k2=2.93×10−12 e−(1710±300)/RT cm3 molecule−1sec−1 with rate constants at 298 °K of k1= (5.25±0.53) ×10−12 cm3 molecule−1sec−1 and k2= (1.64±0.16) ×10−13 cm3 molecule−1sec−1. These rate constants are compared and discussed with literature values.

Rate constants for the reaction of OH radicals with dimethyl ether and vinyl methyl ether over the temperature range 299–427 °K

Absolute rate constants for the reaction of OH radicals with dimethyl ether and vinyl methyl ether have been determined over the temperature range 299–427 °K using a flash photolysis–resonance fluorescence technique. The Arrhenius expressions obtained were k (CH3OCH3) =1.29×10−11 e−(770±300)/RT cm3 molecule−1⋅sec−1, and k (CH2=CHOCH3) =6.10 ×10−12 e(1015±300)/RT cm3 molecule−1⋅sec−1, with rate constants at room temperature of k (CH3OCH3) = (3.50±0.35) ×10−12 cm3 molecule−1⋅sec−1 and k (CH2=CHOCH3) = (3.35±0.34) ×10−11 cm3 molecule−1⋅sec−1.

Rate constants for the reactions of the OH radical with (CH3)2NH, (CH3)3N, and C2H5NH2 over the temperature range 298–426 °K

Rate constants for the reactions of the OH radical with (CH3)2NH, (CH3)3N, and C2H5NH2 have been determined over the temperature range 298–426°K by a flash photolysis–resonance fluorescence technique. The Arrhenius expressions obtained are with rate constants at room temperature of (6.54±0.66) ×10−11, (6.09±0.61) ×10−11, and (2.77±0.28) ×10−11 cm3 molecule−1 sec−1 for (CH3)2NH, (CH3)3N, and C2H5NH2, respectively. Possible mechanisms and atmospheric significance of these reactions are discussed.

Rate constants for the reaction of OH radicals with ethylene over the temperature range 299–425 °K

Absolute rate constants for the reaction of OH radicals with ethylene have been determined, using a flash photolysis–resonance fluorescence technique, over the temperature range 299–425 °K at total pressures of 25–663 torr of argon. The rate constants k2 were observed to be pressure dependent below ∼225 torr total pressure, in agreement with other recent studies. The rate constants were independent of total pressure over the range 225–663 torr of argon, and the Arrhenius expression obtained from data over this pressure range was k2=2.18×10−12 e(770±300)/RT cm3 molecule−1⋅sec−1 with a value at 299 °K of k2= (7.85±0.79) ×10−12 cm3 molecule−1⋅sec−1. This room temperature high pressure rate constant is in good agreement with a recent relative rate determination carried out at atmospheric pressure.

Kinetics of the reactions of OH radicals with C2H2 and CO

Absolute rate constants for the reactions of OH radicals with C2H2 (k1) and CO (k2) have been determined using a flash photolysis–resonance fluorescence technique. Rate constants k1 were determined at room temperature over the pressure range 25–400 torr total pressure of argon, and over the temperature range 298–422 °K at ∼200 torr total pressure of argon. k1 was pressure dependent below ∼200 torr total pressure of argon, but was in the high pressure kinetic region at total pressures ?200 torr. The Arrhenius expression in the high pressure region was k1=1.91×10−12e−(620±400)/RT cm3 molecule−1 sec−1. Rate constants k2 were determined at 299±1 °K with argon and SF6 as diluent gases over the pressure range 25–643 torr total pressure. With argon as the diluent gas k2 showed, within experimental error, little or no pressure dependence as reported earlier from this laboratory. However, with SF6 as the diluent gas k2 increased from (1.53±0.16) ×10−13 cm3 molecule−1 sec−1 at 25 torr total pressure to (3.43±0.35) ...

Rate constants for the reactions of the OH radical with NO2 (M=Ar and N2) and SO2 (M=Ar)

Absolute rate constants for the reactions OH+NO2+M→HNO3+M (M=Ar, N2) OH+SO2+M→HSO3+M (M=Ar) have been determined at 298°K, using a flash photolysis–resonance fluorescence technique. Rate constants k1 and k2 were determined over the pressure range 25–648 torr for M=Ar, while a rate constant for the first reaction was also obtained for M=N2 at 25 torr total pressure. The low pressure third order rate constants were determined to be k1(M=Ar) = (1.02±0.10) ×10−30 cm6 molecule−2⋅sec−1 and k2(M=Ar) = (1.64±0.33) ×10−31 cm6 molecule−2⋅sec−1, in reasonable agreement with the literature values. The bimolecular rate constants at 760 torr total pressure were determined to be kbi1= (5.9±0.7) ×10−12 cm3 molecule−1⋅sec−1 (M=Ar), kbi1= (6.4±1.0) ×10−12 cm3 molecule−1⋅sec−1 (M=N2), and kbi2= (6.7±0.7) ×10−13 cm3 molecule−1⋅sec−1 (M=Ar). Extrapolation of the data led to limiting high pressure second order constants of k∞1?8.5×10−12 cm3 molecule−1⋅sec−1 and k∞2?8.3×10−13 cm3 molecule−1⋅sec−1.

Absolute rate constants for the reaction of OH radicals with allene, 1,3‐butadiene, and 3‐methyl‐1‐butene over the temperature range 299–424 °K

Absolute rate constants for the reaction of OH radicals with allene, 1,3‐butadiene, and 3‐methyl‐l‐butene have been determined over the temperature range 299–424 °K, using a flash photolysis–resonance fluorescence technique. The Arrhenius expressions obtained were k (allene) =5.59×10−12 e(305±300)/RT cm3 molecule−1 sec−1, k (1,3‐butadiene) =1.45×10−11 e(930±300)/RT cm3 molecule−1 sec−1, k (3‐methyl‐1‐butene) =5.23×10−12 e(1060±300)/RT cm3 molecule−1 sec −1, with rate constants at room temperature of (9.30±0.93) ×10−12, (6.85±0.69) ×10−11, and (3.10±0.31) ×10−11 cm3 molecule−1 sec−1 for allene, 1,3‐butadiene, and 3‐methyl‐l‐butene, respectively.

Rate constants for the reaction of OH radicals with CHFCl2 and CH3Cl over the temperature range 298–423 °K, and with CH2Cl2 at 298 °K

Rate constants for the reaction of OH radicals with CHFCl2 and CH3Cl have been determined over the temperature range 298–423 °K using a flash photolysis–resonance fluorescence technique. The Arrhenius expressions obtained were k1(CHFCl2) =1.75×10−12e−(2490±300)/RT cm 3 molecule−1 sec−1, k1(CH3Cl) =4.1×10−12 e−(2700±300)/RT cm3 molecule−1 sec−1. In addition, the rate constant for the reaction of OH radicals with CH2Cl2 was determined to be k1(CH2Cl2) = (1.45±0.20) ×10−13 cm3 molecule−1 sec−1 at 298.5 °K. These rate constants are in good agreement with literature values.