Direct measurement of the reaction CH3+OH and its pathways between 300 and 480 K

Oser, Harald; Stothard, N.D.; Humpfer, R.; Grotheer, Horst-Henning; Just, Th.

doi:10.1016/s0082-0784(06)80073-1

Cited by 16 publications

(36 citation statements)

References 17 publications

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“…If this was true, it was to be expected that this channel may be a product route of the reaction CH3 + OH even at ambient temperature. In fact we failed to detect any signals of Ha and/or HCOH/HzCO in our low temperature studies [4,5] between 300 and 500 K nor found anything else in these channels experimentally. At 700 K, however, we clearly observed a primary formation of molecular hydrogen along with 30 amu signals from HCOH and/or H2CO.…”

Section: Introductioncontrasting

confidence: 57%

“…As pointed out in our earlier studies [4,5], due to the presence of a large excess of H20 needed for the OH source, reaction (161, i.e., 'CH2 + H2O + CH3 + OH which is the reverse of (Id) drives this latter reaction in an early steady state (for other products of rc. 16 see below).…”

Section: Reaction Products For Ch3 + Oh At 700 Kmentioning

confidence: 74%

“…The need to calibrate both reactants and to measure both types of profiles contrasts to the more commonly studied radical/atom + inert molecule systems. OH source: As described in our earlier articles [4,5] we used OH as excess component and prepared it at the upstream end of the reactor in a fixed source by applying the well-known reaction HzO + F -OH + HF, the F atoms being generated in a microwave discharge of Fz diluted in He. The OH concentration was determined using a scavenger gas which was added to the flow through the movable injector and thus enabled us to measure the OH profiles in the absence of CH3.…”

Section: Generation and Calibration Of Radicalsmentioning

confidence: 99%

“…This is seen in the insert of Figure 3 showing log[CH31 curves with slopes increasing with reaction time. The effect of the OH profile and how it enters the simulation are discussed in [4,5].…”

Section: Measurement Of the Excess Component Ohmentioning

confidence: 99%

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Formation of HCOH + H₂ through the reaction CH₃ + OH. Experimental evidence for a hitherto undetected product channel

Humpfer¹,

Oser²,

Grotheer³

1995

Int J of Chemical Kinetics

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In an extension of our earlier studies at lower temperatures [4,51 the title reaction was measured directly in a flow reactor at temperatures of 600 and 700 K. The pressure of 0.65 mb was chosen that low in order to reduce the contribution of the stabilization channel. OH was used in an excess over CH3. Both reactants along with the reaction products were monitored by mass spectrometry. CH3 profiles served as the major observable quantity for the extraction of rate data. This had to be done by using computer simulation since it was impossible to work under pseudo-first-order conditions.The obtained total rate coefficients were divided into channel rate coefficients by means of branching ratios as determined by the mass spectrometric measurement of the reaction products. For CH3 + OH, this led to a rate coefficient, k l , into the stabilization channel, and another one, kl,+f referring to the sum of two Hz-eliminating channels yielding the biradical HCOH and to a minor extent H2CO. These latter channels have not been measured before.In order to distinguish between them we switched over from OH to OD to get(1'0 -HzCO + HD so that the biradical and/or aldehyde channels could be determined by their by-products Hz and HD, respectively. The use of OD makes it also possible to measure the channelthrough its by-product, HDO.within our error limits no significant isotope effect takes place. units of cm, molec, and s:A comparison of the rate coeficients of both systems, i.e., CH3 + OH and CH3 + OD, indicates thatFor the rate coefficient into the HCOH channel, we arrive at a preliminary Arrhenius expression in k1, = 9.1 x 10-l~ exp(-1500/~).The H2CO channel could not be detected at our lower temperature rendering us with a rate coefficient at 700 K klf(700 K) = 1.7 X 10-l'Since simulation is needed for the deduction of the total rate coefficients as well as of the branching ratios, an uncertainty factor of 1.5 has to be attributed to these numbers. 0

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Section: Introductioncontrasting

confidence: 57%

Section: Reaction Products For Ch3 + Oh At 700 Kmentioning

confidence: 74%

Section: Generation and Calibration Of Radicalsmentioning

confidence: 99%

Section: Measurement Of the Excess Component Ohmentioning

confidence: 99%

See 2 more Smart Citations

Formation of HCOH + H₂ through the reaction CH₃ + OH. Experimental evidence for a hitherto undetected product channel

Humpfer¹,

Oser²,

Grotheer³

1995

Int J of Chemical Kinetics

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“…Figure 6 shows a comparison of our calculated rate constants (obtained from MRPT(6,4)/ACCD//CAS(6,4)/ACCD data and related dissociation rate constants and equilibrium constants) and literature data. [57][58][59][60][61][62][63] These recombination rate constants (in cm 3 molecule À1 s À1 ) are best fitted to:…”

Section: Ohmentioning

confidence: 99%

Implementation of a variational code for the calculation of rate constants and application to barrierless dissociation and radical recombination reactions: CH₃OH = CH₃ + OH

Oliveira¹,

Bauerfeldt²

2012

Int J of Quantum Chemistry

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Here, a new implementation for calculating canonical variational rate constants is introduced and tested against methanol dissociation rate constants and the (high pressure) radical recombination reaction, CH 3 þ OH ! CH 3 OH. Reaction paths are described at the CASSCF level, with energy corrections at MRMP2. Molecular properties for both stationary and non-stationary points along the reaction path are used for the calculation of rate constants. Different models for the low vibrational frequencies are discussed: harmonic oscillator and free rotor models. The CH 3 þ OH ! CH 3 OH recombination rate constants are determined from dissociation rate constants and equilibrium constants. Our calculated rate constants agree with previously reported data for these reactions, suggesting the good performance of our implemented code in calculating canonical variational rate constants. The rate expressions are suggested: as: k dis (T) ¼ 8.42 Â 10 þ16 Â e À96.18/RT and k rec (T) ¼ 2.05 Â 10 À10 Â (T/298) À0.24 Â e À0.30/RT , in units s À1 and cm 3 molecule À1 s À1 , respectively, and over the temperature range 300-2000 K, with activation energies in kcal/mol.

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Involvement of the notch pathway in the regulation of matrix metalloproteinase 13 and the dedifferentiation of articular chondrocytes in murine cartilage

Blaise

Mahjoub

Salvat

et al. 2009

Arthritis & Rheumatism

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Objective. To demonstrate the activation of the Notch signaling pathway during changes in the phenotype of chondrocytes in vitro, and to assess the influence of Notch on the production of chondrocyte markers.Methods. Serial monolayer primary cultures of murine articular chondrocytes (MACs), as a model of chondrocyte dedifferentiation, were prepared. MACs were cultured with or without a Notch inhibitor and transfected with different Notch-expressing vectors. The Notch pathway and chondrocyte marker profiles were assessed by quantitative reverse transcriptionpolymerase chain reaction, immunoblotting, and immunocytochemistry.Results. Successive passages of MACs resulted in a loss of type II collagen and aggrecan (chondrocyte differentiation markers), an increase in type I collagen (dedifferentiation marker), an increase in Notch ligands, and augmented target gene activity. The Notch inhibitor decreased the type II collagen protein content but had no effect on Col2a1 messenger RNA, while transfection with the constitutive active forms of the Notch1 receptor led to a decrease in type II collagen in transfected cells. In assays to investigate the mechanism of type II collagen breakdown, matrix metalloproteinase 13 (MMP-13) synthesis was regulated in a Notchdependent manner, whereas MMP-2 synthesis was unchanged.Conclusion. The Notch signaling pathway is associated with decreased type II collagen production during the dedifferentiation of MACs in vitro. This may be correlated with the increase in MMP-13 production linked to activation of Notch.

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Direct measurement of the reaction CH3+OH and its pathways between 300 and 480 K

Cited by 16 publications

References 17 publications

Formation of HCOH + H₂ through the reaction CH₃ + OH. Experimental evidence for a hitherto undetected product channel

Formation of HCOH + H₂ through the reaction CH₃ + OH. Experimental evidence for a hitherto undetected product channel

Implementation of a variational code for the calculation of rate constants and application to barrierless dissociation and radical recombination reactions: CH₃OH = CH₃ + OH

Involvement of the notch pathway in the regulation of matrix metalloproteinase 13 and the dedifferentiation of articular chondrocytes in murine cartilage

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Direct measurement of the reaction CH3+OH and its pathways between 300 and 480 K

Cited by 16 publications

References 17 publications

Formation of HCOH + H2 through the reaction CH3 + OH. Experimental evidence for a hitherto undetected product channel

Formation of HCOH + H2 through the reaction CH3 + OH. Experimental evidence for a hitherto undetected product channel

Implementation of a variational code for the calculation of rate constants and application to barrierless dissociation and radical recombination reactions: CH3OH = CH3 + OH

Involvement of the notch pathway in the regulation of matrix metalloproteinase 13 and the dedifferentiation of articular chondrocytes in murine cartilage

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Formation of HCOH + H₂ through the reaction CH₃ + OH. Experimental evidence for a hitherto undetected product channel

Formation of HCOH + H₂ through the reaction CH₃ + OH. Experimental evidence for a hitherto undetected product channel

Implementation of a variational code for the calculation of rate constants and application to barrierless dissociation and radical recombination reactions: CH₃OH = CH₃ + OH