Singlet methylene removal by saturated and unsaturated hydrocarbons

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

doi:10.1016/0010-2180(94)00149-m

Cited by 21 publications

(39 citation statements)

References 33 publications

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“…[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%

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: Methodsmentioning

confidence: 99%

Temperature Dependences of Singlet Methylene Removal Rates

and¹,

Lawrance²,

and³

et al. 1996

J. Phys. Chem.

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“…The errors quoted correspond to 2u statistical errors from the weighted linear least-squares analysis plus estimated errors due to uncertainties in flow rates and total pressure. The uncertainties in flow rates were estimated from the manufacturer's published data and the experimental errors in our measurements of the flowmeter gas correction factors for the gases involved as described in a previous publication [18]. This rate constant may be compared with those for CH4 and SiH4, which have been reported previously.…”

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confidence: 99%

“…The intercept corresponds to the measured pseudo-first-order removal rate constant for the concentrations of CHzCO and N2 in the reaction mixture [14,17,18]. The errors quoted correspond to 2u statistical errors from the weighted linear least-squares analysis plus estimated errors due to uncertainties in flow rates and total pressure.…”

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confidence: 99%

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Comparison of singlet methylene removal rates by group IV hydrides

Gutsche

Lawrance

Staker

et al. 1995

Int J of Chemical Kinetics

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The technique of laser flash photolysisflaser absorption has been used to obtain an absolute removal rate constant of (3.85 2 0.18) X cm3 molecule-' s-l for singlet methylene, lCHz (glA1), with germane (Ge&) at ambient temperature. The removal rate constant is compared with the values for methane (CH4) and silane (SiH4) which have been determined previously. 0 1995 John Wiley & Sons, Inc.The simplest carbene, methylene (CHz), possesses a distinctive chemistry, playing significant roles in such reaction systems as flames, combustion, and planetary atmospheres. Carbenes form an important class of reactive intermediates in organic chemistry. The fundamental importance of CH2 has resulted in a significant literature devoted to this species in recent years [l]. An increased interest in the gas-phase kinetic studies of CH2 has occurred, largely due to the case with which the metastable singlet state (5lA1, abbreviated lCH2) may be observed by techniques such as laserinduced fluorescence (LIF) and laser resonant absorption (LRA). Since the first study [2] of lCH2 reaction rates using a direct method, several groups have measured bimolecular removal rate constants for lCH2 with a wide range of organic and inorganic molecules using laser-based methods 13-171.While removal rate constants have been measured for lCH2 reacting with a range of organic compounds, there has yet to be any detailed studies of reactions with organometallics. In this study we have used the technique of laser flash photolysisfiaser absorption to determine the absolute rate constant for the removal of lCH2 by germane (GeH4) at ambient temperature (298 * 2 K), apparently for the first time. The removal rate constant is compared with those measured previously for lCH2 with methane (CH4) and silane (SiH4).

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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: 97%

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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Singlet methylene removal by saturated and unsaturated hydrocarbons

Cited by 21 publications

References 33 publications

Temperature Dependences of Singlet Methylene Removal Rates

Temperature Dependences of Singlet Methylene Removal Rates

Comparison of singlet methylene removal rates by group IV hydrides

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

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