Removal Rate Constants for Singlet Methylene with Oxygen-Containing Organic Species

Gutsche, Greg J.; Lawrance, Warren D.; Staker, Warren S.; King, Keith D.

doi:10.1021/j100031a013

Cited by 11 publications

(28 citation statements)

References 8 publications

(10 reference statements)

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“…Of the other species shown in Table 2, reaction of 1 CH 2 with alcohols probably involves insertion into the O-H bond which is significantly more reactive than C-H bonds, 15 and, as discussed by us previously, 15 aldehydes and ketones, including formaldehyde, can react with 1 CH 2 to form CdO insertion products. 39 This may occur via attachment of 1 CH 2 to the 1 CH 2 + CH 4 f [C 2 H 6 ]* f CH 3 + CH 3 1 oxygen atom forming the [H 2 C-O-CH 2 ]* intermediate complex in the case of formaldehyde or the [CH 2 C-O-CH 2 ]* complex in the case of ketene, followed by rearrangement, or by direct insertion into the CdO double bond.…”

Section: Discussionmentioning

confidence: 73%

“…As discussed previously, the relative precision of the rate constants is better than is indicated by the quoted errors. 15 The temperature dependences of the 1 CH 2 bimolecular removal rate constants were investigated typically at six temperatures for each substrate over the range of ca. 298-462 K. The rate constants were fitted to the normal Arrhenius equation given by …”

Section: Resultsmentioning

confidence: 99%

“…[13][14][15][16] We give here a brief overview and provide details relevant to the temperature dependence experiments. The same stainless steel reaction cell is used for the high-temperature work as was used for the ambient temperature studies.…”

Section: Methodsmentioning

confidence: 99%

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Temperature Dependences of Singlet Methylene Removal Rates

and¹,

Lawrance²,

and³

et al. 1996

J. Phys. Chem.

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The technique of laser flash photolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene, 1 CH 2 (a ˜1A 1 ), in the temperature range 298-462 K. The temperature dependences of the removal rate constants for N 2 , CH 4 , C 2 H 4 , C 2 H 6 , H 2 O, H 2 CO, CH 2 CO, CH 3 F, C 2 F 6 , and CH 3 OH were measured and the Arrhenius parameters determined. For the reacting species, CH 4 , C 2 H 4 , C 2 H 6 , H 2 O, H 2 CO, CH 2 CO, CH 3 F, and CH 3 OH, the rate constants exhibit negative temperature dependences with activation energies covering the range -0.7 ( 0.7 kJ mol -1 for CH 3 F to -3.5 ( 1.0 kJ mol -1 for CH 3 OH. In contrast, positive temperature dependences are observed for the nonreacting species, N 2 and C 2 F 6 , with activation energies of 1.8 ( 0.9 and 1.6 ( 2.0 kJ mol -1 , respectively. Good agreement was obtained with previously reported measurements for the N 2 , CH 4 , CH 2 CO, C 2 H 4 , and C 2 H 6 temperature dependences. For the nonreacting species, comparison is made with theoretical predicted temperature dependences for collision-induced intersystem crossing from 1 CH 2 (a ˜1A 1 ) to 3 CH 2 (X ˜3B 1 ).

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Section: Discussionmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 99%

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Temperature Dependences of Singlet Methylene Removal Rates

and¹,

Lawrance²,

and³

et al. 1996

J. Phys. Chem.

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“…This effect has also been seen in our previous kinetic studies of singlet CH 2 and SiH 2 . [16][17][18][21][22][23][24][25][26][27][28] We have shown previously that the rate constants are independent of photolysis wavelength, indicating that vibrational relaxation is not an issue in this system. 9 The rate constants reported here were obtained with total cell pressures in the range 10-200 Torr.…”

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confidence: 99%

Rate constants for the gas-phase reactions of germylene with CH3OCH3, CH3OH, CD3OD and D2O at ambient temperature

Alexander

King

Lawrance

2003

Phys. Chem. Chem. Phys.

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Gas-phase rate constants for the reactions of germylene, GeH 2 , with dimethylether (CH 3 OCH 3 ), methanol (CH 3 OH), deuterated methanol (CD 3 OD), and deuterated water (D 2 O), have been determined at ambient temperature (295 K) and total pressures over the range 10-200 Torr of the bath gas SF 6 . The second-order rate constants are pressure dependent up to the maximum pressures investigated. The behaviour of GeH 2 with these reactants is very similar to the behaviour observed for silylene, SiH 2 . Over the same pressure range the GeH 2 reaction rate constants are smaller than those observed for SiH 2 .

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“…The particular apparatus and techniques used in our studies of singlet methylene have been presented in detail in previous publications describing our (0,0,0) ambient and temperature dependent studies [19,20,[22][23][24][25][26][27]. We here give a brief overview, and provide details relevant to the (0,1,0) experiments.…”

Section: Methodsmentioning

confidence: 99%

Singlet Methylene Removal Rate Constants from the (0,1,0) Vibrational Level: Enhancement via Complex-Mediated Vibrational Relaxation

Buntine¹,

Gutsche²,

Staker³

et al. 2001

Zeitschrift Für Physikalische Chemie

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The technique of laser flash photolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene, 1 CH 2 (ã 1 A 1 ), from the vibrationally excited (0,1,0) level. (0,1,0) removal rate constants are reported for the 13 species N . With the exception of the slowest three reacting species, CH 4 , CH 3 F and C 2 F 4 , for the species which are known to react from the (0,0,0) level the removal rate constants are essentially identical for the (0,0,0) and (0,1,0) levels. The removal rate constants for CH 4 , CH 3 F and C 2 F 4 increase by factors of 1.2, 2.2 and 1.45 respectively with vibrational excitation to (0,1,0). For the species N 2 , CF 4 , and C 2 F 6 , which do not appear to react from (0,0,0), the removal rate constants are increased in the (0,1,0) state. The increase is very large for N 2 , for which the factor is 4, and is substantial for CF 4 and C 2 F 6 , which show factors of 2.55 and 2.7 respectively. The increased removal rate constants for N 2 and for the fluorine-containing species are attributed to the formation of an association complex between 1 CH 2 (0,1,0) and the partner followed by dissociation to 1 CH 2 (0,0,0) and the partner. We refer to this as complex-mediated vibrational relaxation (CMVR). Removal rate constants for the (0,0,0) level are likely to be in error when experimental conditions allow the simultaneous production of 1 CH 2 (0,1,0) from the methylene precursor and where CMVR, which typically has comparable efficiency to collision induced intersystem crossing, provides a growth term for the (0,0,0) population. The species for which CMVR is likely to be significant are those for which reaction is either absent or a minor pathway and where there are electron-rich centres for the empty orbital of 1 CH 2 to "bind", allowing the formation of a long lived 1 CH 2 -collider complex.

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Removal Rate Constants for Singlet Methylene with Oxygen-Containing Organic Species

Cited by 11 publications

References 8 publications

Temperature Dependences of Singlet Methylene Removal Rates

Temperature Dependences of Singlet Methylene Removal Rates

Rate constants for the gas-phase reactions of germylene with CH3OCH3, CH3OH, CD3OD and D2O at ambient temperature

Singlet Methylene Removal Rate Constants from the (0,1,0) Vibrational Level: Enhancement via Complex-Mediated Vibrational Relaxation

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