IUPAC Subcommittee on Gas Kinetic Data Evaluation

Providing evaluated kinetic data on the web since 1999.

IUPAC Subcommittee on Gas Kinetic Data Evaluation

Website: http://www.iupac-kinetic.ch.cam.ac.uk/ See website for latest evaluated data. Datasheets can be downloaded for personal use only and must not be retransmitted or disseminated either electronically or in hardcopy without explicit written permission.

This datasheet last evaluated: 2006-08-01 ; last change in preferred values: 2006-08-01 ; last peer-reviewed publication: 2004-03-09


HO + CH3SCH3H2O + CH2SCH3 (1) Δ Hο = -105 kJ mol-1
HO + CH3SCH3CH3S(OH)CH3 (2) Δ Hο ∼ approx -43 kJ mol-1
HO + CH3SCH3CH3S + CH3OH (3) Δ Hο = -77 kJ mol-1
HO + CH3SCH3CH3 + CH3SOH (4) Δ Hο ∼ approx 0 kJ mol-1

Rate Coefficient Data

Absolute Rate Coefficients

Rate Coefficient (k) / Temperature / ReferenceTechniques and Comments
cm3molecule-1s-1Kelvin
k 1 = 6.8×10 -11 exp[-(138±46)/T]248–363Wine et al., 1981FP-RF
k 1 = (4.26 ± 0.56)×10 -12 298
k 1 = (3.22 ± 1.16)×10 -12 298Martin et al., 1985DF-EPR
k 1 = 2.5×10 -12 exp[-(130±102)/T]297–400Wallington et al., 1986FP-RF
(6.28 ± 0.10)×10 -12 (1 bar of air)298Hynes et al., 1986PLP-LIF (a)
k 1 = 1.36×10 -11 exp[-(332±96)/T]276–397Hynes et al., 1986FP-RF
k 1 = 4.46×10 -12 298
k 1 = 1.18×10 -11 exp[-(236±150)/T]260–393Hsu et al., 1987DF-RF (b)
k 1 = (5.54 ± 0.15)×10 -12 298
k 1 = 1.35×10 -11 exp[-(285±135)/T]297–368Abbatt et al., 1992DF-LIF (c)
k 1 = (4.98 ± 0.46)×10 -12 297 ± 2
k 1 = (4.95 ± 0.35)×10 -12 298Barone et al., 1996PLP-LIF

Relative Rate Coefficients

Rate Coefficient (k) / Temperature / ReferenceTechniques and Comments
cm3molecule-1s-1Kelvin
k 1 = (5.00 ±0.50)×10 -12 296Wallington et al., 1986RR-FTIR (d)
k = (8.00 ±0.20)×10 -12 (1 bar air)296
k 1 = (4.40 ±0.40)×10 -12 298Barnes et al., 1988RR-GC (e)
k = (8.00 ±0.50)×10 -12 (1 bar air)298
k = 1.56×10 -12 exp[(369±27)]/T250–299Albu et al., 2006RR-FTIR (f)
[O 2 ] = 0 mbar
k = 1.31×10 -14 exp[(1910±69)]/T
[O 2 ] = 207 mbar
k = 1.56×10 -12 exp[(1587±24)]/T
[O 2 ] = 380 mbar
k = (780 ± 1.80)×10 -12 (1 bar air)298

Branching Ratios

Branching RatioTemperature / ReferenceTechniques and Comments
Kelvin
k 1 /k = 0.84 ± 0.15298Stickel et al., 1993(g)
k 1 /k = 0.84 ± 0.26298Turnipseed et al., 1996(h)
k 3 /k < 0.04298Turnipseed et al., 1996(i)
k 4 /k < 0.07298Zhao et al., 1996(j)

Comments

(a) The effect of O 2 was investigated over the temperature range 261–321 K. The measured rate coefficient was observed to depend on the O 2 concentration, and the rate coefficient given in the table is that measured at 1 bar (750 Torr) total pressure of air. The rate coefficient measured in the absence of O 2 is ascribed to reaction (1).

(b) Rate coefficient not affected by the addition of up to 1.3 mbar (1 Torr) of O 2 .

(c) HO generated from the H + NO 2 reaction. The total pressure was varied over the range 14.1–130 mbar (10.6–97.5 Torr) of N 2 . The measured rate coefficient was invariant to the total pressure over this range.

(d) Reference reactant was cyclohexane. The measured ratio k(HO + CH 3 SCH 3 ) / k(HO + cyclohexane) was converted to an absolute rate coefficient using k(HO + cyclohexane) = 6.92 ×10 -12 cm 3 molecule -1 s -1 (Atkinson, 2003).

(e) Reference reactant was ethene. Rate coefficient ratios, k(HO + CH 3 SCH 3 ) / k(HO + ethene) at various partial pressures of O 2 in a total pressure of 1 bar were converted to an absolute rate coefficient using k(HO + ethene) = 8.0 ×10 -12 cm 3 molecule -1 s -1 .

(f) Mainly C 2 H 4 but also C 3 H 6 and 2-methylpropene were used as reference reactants with k(HO + C 2 H 4 ) = 1.96 × 10 -12 exp(438/T), k(HO + C 3 H 6 ) = 4.85 × 10 -12 exp(504/T), k(HO + C 2 H 4 ) = 9.47 × 10 -12 exp(504/T), Atkinson, 1997).

(g) For the reaction DO + CH 3 SCH 3 , HDO was monitored by tunable diode laser absorption spectroscopy, and the branching ratio obtained by assuming a unit HDO yield from the DO radical reaction with n-hexane and cyclohexane. The branching ratio was independent of total pressure of N 2 [13–40 mbar (10–30 Torr)], temperature (298–348 K) and replacement of 13 mbar (10 Torr) total pressure of N 2 by 13 mbar total pressure of O 2 . From the temporal profiles of the HDO signals, rate coefficients k 1 for the reaction of the DO radical with CH 3 SCH 3 of (5.4 ± 0.4)×10 -12 cm 3 molecule -1 s -1 at 298 K and 13 mbar (10 Torr) N 2 , (5.8 ± 1.9)×10 -12 cm 3 molecule -1 s -1 at 298 K and 40 mbar (30 Torr) N 2 , and (4.4 ± 1.0)×10 -12 cm 3 molecule -1 s -1 at 348 K and 13 mbar (10 Torr) N 2 were also obtained, in agreement with the rate coefficients for the HO radical reaction.

(h) Indirect measurement of CH 3 SCH 2 by addition of O 2 and NO and measuring CH 3 S formation by LIF.

(i) Direct detection of CH 3 S by LIF

(j) Direct detection of CH 3 using TDLAS

Preferred Values

k1cm3molecule-1s-14.8-124.8×10-12±0.10  if   T 298 k2cm3molecule-1s-12.2-122.2×10-12±0.2  if   T 298   and   P 1 bar air k1cm3molecule-1s-1{4.8-124.8×10-12±0.10  if   T 298 1.12-11PlusMinus -250150 T1.12×10-11exp( -250±150)/T  if   240 T 400 k2cm3molecule-1s-19.5-39 O_2[O2] 5270 T1 7.5-29 O_2[O2] 5610 T9.5×10-39 O_2[O2]O_2[O2]exp( 5270 /T)/{1+ 7.5×10-29 O_2[O2]O_2[O2]exp( 5610 /T)}  if   240 T 360   and   P 1 bar

Comments on Preferred Values

It is now recognized (Hynes et al., 1986; Barone et al., 1996; Atkinson, 1994; Wallington et al., 1986; Barnes et al., 1988; Albu et al., 2006) that this reaction proceeds via the two reaction steps (1) and (2). The CH 3 S(OH)CH 3 adduct radical decomposes sufficiently rapidly such that in the absence of O 2 only the rate coefficient k 1 is measured. In the presence of O 2 the CH 3 S(OH)CH 3 radical reacts by CH 3 S(OH)CH 3 + O 2 products. Hence only in the presence of O 2 is the addition channel (2) observed, with the rate coefficient being dependent on the O 2 concentration but, to at least a first approximation, not on the concentration of other third bodies such as N 2 , Ar or SF 6 (Hynes et al., 1986; Abbatt et al., 1992). HO 2 is formed at 50% yield in the reaction of CH 3 S(OH)CH 3 with O 2

The most recent absolute rate coefficients measured in the absence of O 2 (Wine et al., 1981; Hynes et al., 1986; Hsu et al., 1987; Abbatt et al., 1992; Barone et al., 1996) confirm that the earlier absolute rate coefficients of Atkinson et al. (1978) and Kurylo (1978) are erroneously high, and those of Mac Leod et al. (1984) were in error because of wall reactions. Wine et al., (1981), Hynes et al. (1986), Hsu et al.(1987) and Abbatt et al. (1992) all determined a positive dependence on temperature for the abstraction process. In contrast, Wallington et al. (1986) and Albu et al. (2006) found slight negative temperature dependences. Albu et al. (2006) could not rule out that this is due to the presence of O 2 impurity in their relative rate experiments at atmospheric pressure. The relative rate study of Wallington et al. (1986) showed that previous relative studies carried out in the presence of NO were dubious. The preferred rate coefficients k 1 for the abstraction channel (1) are therefore based on the studies of Wine et al. (1981), Hynes et al. (1986), Hsu et al. (1987), Abbatt et al.(1992) and Barone et al. (1996).

The dependence of k on [O 2 ] has been investigated by Wallington et al. (1986), Barnes et al. (1988), Hynes et al. (1986), Williams et al. (2001) and Albu et al. (2006). Hynes et al (1986), Williams et al (2001) and Albu et al. (2006) show that the degree of enhancement of the overall rate coefficient due to O 2 is strongly temperature dependent.

The rate coefficient given for the HO radical addition channel (2) utilises the data of Hynes et al. (1986), Williams et al. (2001) and Albu et al (2006). The expression for k 2 reproduces the [O 2 ] and temperature dependence of k obs ( (k obs = k 1 + k 2 + k 3 + k 4 k 1 +k 2 ) ) of Hynes et al. (1986), Williams et al. (2001) and Albu et al. (2006) at pressures close to one atmosphere (where the rate coefficients for HO addition to CH 3 SCH 3 and the reverse dissociation step may be in the falloff region). The recommended parameterisation returns a room temperature overall rate coefficient (k 1 +k 2 ) for 1 bar of air of k = 7 × 10 -12 cm 3 molecule -1 s -1 , which lies between values of 8 × 10 -12 cm 3 molecule -1 s -1 , obtained in relative rate measurements in one atmosphere of air (Wallington et al., 1986; Barnes et al., 1988; Albu et al., 2006) and the Hynes et al. (1986) absolute value of 6.3 × 10 -12 cm 3 molecule -1 s -1 , The agreement at lower temperatures is even better than this.

References

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