The Oxidation of Formyl Radicals

Washida, Nobuaki; Martinez, Richard I.; Bayes, Kyle D.

doi:10.1515/zna-1974-0211

Cited by 74 publications

(47 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, conventional reaction schemes cannot rationalize H2 formation in a chain for experiments a t 25°C. The formyl radicals formed in the CH20-02 system will react almost exclusively with 0 2 , even in experiments at Poz = 0.05 torr, and H2 formation through reaction (4), which may occur in 02-free CH2O photolyses at 25"C, is unimportant here [21,22,30,31]. However, H2 formation through reaction (3) is expected to compete with the H-atom reaction ( 6 ) with 0 2 for the relatively low [02]/[CH20] ratios that we employed.…”

Section: 25(----)mentioning

confidence: 91%

“…Reaction (17) is exothermic by 33 kcal/mol, and it is conceivable that a fair fraction of the reaction will proceed by reaction (16) in which the initial HCO product will contain more than the -18 kcal/mol necessary for the decomposition of the radical: (16) and (19), all the CO molecules formed in CH2O-02 mixture photolysis a t 25°C must be generated in reactions (2) and (8), and for these conditions one expects +co -+ H~ 5 41 = 0.68; this is contrary to the experimental results. By analogy with the proposed HO2 radical addition to CH20, reaction (21), the addition of the peroxyformyl radical to CH20, and the subsequent rearrangement by H-atom transfer should be considered as well: (21) HCOOz + CH2O + (HC002CH20) -HC02 + HCOZH The relative insensitivity of + H~ to variations in the absorbed light intensity (Table 11) points to the first-order termination of the radical chains at the wall of the reaction cell for our conditions. A reaction such as (22) is suggested: Table 11) as a result of the slowing of the diffusion of HO2 (and/or other chain-carried radicals) to the wall and the increased length of the chains which would result for these conditions.…”

Section: Hco2(+ M) + H + C02(+ M)mentioning

confidence: 93%

“…There has been considerable interest in recent years concerning the relative importance of the two competing reactions (7) and (8) (8) is dominant [21,22,30]. However, in the recent study of the C1-atom-sensitized decomposition CH20-02 mixtures, Osif and Heicklen [14,15] estimated the ratio of R7/R8 z 5 f 1, independent of the pressure in the range of 60-700 torr.…”

Section: Mechanism Of the Formyl Radical Reactions With 0mentioning

confidence: 99%

See 2 more Smart Citations

Unusual H₂‐forming chain reaction in the 3130‐Å photolysis of formaldehyde‐oxygen mixtures at 25°C

Horowitz

Calvert

1978

Int J of Chemical Kinetics

View full text Add to dashboard Cite

A kinetic study has been made of the 3130-A photolysis of CH2O (8 torr) in 02-containing mixtures (0.02-8 torr) and in the presence of added CO2 (&300 torr) a t 25°C. Quantum yields of formation of H2, CO, and C02 and the loss of 0 2 were measured. + H~ and *co were much above unity. In an explanation of these unexpected results, a new H-atom-forming chain mechanism was postulated involving HO2 and HO addition to CH20: CH2O + hv -H + HCO (1) (18). When the results are rationalized in terms of this mechanism, the data suggest k16 >> k 17 and k16/k18 2 0.5. The data require that a reassessment of the relative rates of reactions (7) and (8) be made, since in the previous work HC02H formation was used as a monitor of the rate of reaction (7): HCO + 0 2 + M -HCOO2 + M (7). The present data from experiments at P C H~O = 8 torr and Po, = 1 4 torr give k7[M]/(k? [M] + kg) L 0.049 f 0.017. These data coupled with the k8 estimates of Washida and coworkers give k7 L (4.4 f 1.6) X 10" l2/mol2.sec for M = CH20. The reaction sequence proposed here is consistent with the observed detrimental effect of 0 2 addition on the laser-induced isotope enrichment in HDCO. In additional studies of CHzO-02-isobutene mixtures it was found that +H, was equal to 6 2 as estimated in 02-free CHzO-isobutene mixtures. These results suggest that the increase in CO (u = 1) product observed with O2 addition in CHPO photolysis does not result from perturbations in the fragmentation pattern of the excited CH20, but it is likely that it originates in the occurrence of the exothermic reaction HCO + 0 2 -HOz + CO ( u = 1).

show abstract

Section: 25(----)mentioning

confidence: 91%

Section: Hco2(+ M) + H + C02(+ M)mentioning

confidence: 93%

Section: Mechanism Of the Formyl Radical Reactions With 0mentioning

confidence: 99%

See 1 more Smart Citation

Unusual H₂‐forming chain reaction in the 3130‐Å photolysis of formaldehyde‐oxygen mixtures at 25°C

Horowitz

Calvert

1978

Int J of Chemical Kinetics

View full text Add to dashboard Cite

show abstract

“…Propionaldehyde Buryraldehyde H e t h v l nitrake E t h y l n i t r a t e I -B u t y l "lCralr a The radical input rate is the rate of reaction (131) required to make calculated rates of NO conversion or 0 9 production fit the experimental data. Fits are measured by % error [ 100 X (calc -expt)/expt] for times, and by calc/expt yield ratios for product yields.…”

Section: -B U~y L Nitrate Minor P R O D U C T S Y I E L D Smentioning

confidence: 99%

“…a All rate constants are given for 30°C. b Units: First order = see-', second order = cm3/molec.sec, third order = cm6/molec2-sec, zero order [reaction (131) only] = molec/cm3-sec.…”

Section: (3)mentioning

confidence: 99%

Computer modeling of smog chamber data: Progress in validation of a detailed mechanism for the photooxidation of propene and n‐butane in photochemical smog

Carter

Lloyd

Sprung

et al. 1979

Int J of Chemical Kinetics

162

153

View full text Add to dashboard Cite

A detailed mechanism is presented far reactions occurring during irradiation of part-permillion concentrations of propene and/or n-butane and oxides of nitrogen in air. Data from an extensive series of well-characterized smog chamber experiments carried out in our 5800-liter evacuable chamber-solar simulator facility designed for providing data suitable for quantitative model validation were used to elucidate several unknown or uncertain kinetic parameters and details of the reaction mechanism.The mechanism was then tested against the data base from the smog chamber runs. In general, most calculated concentration-time profiles agreed with experiments to within the experimental uncertainties. Fits were usually attained to within f20% or better for ozone, NO, propene, and n-butane, to within -+30% or better for NOz, PAN, methyl ethyl ketone, 2-butyl nitrate, butyraldehyde, and (in runs not containing propene) methyl nitrate, to within --f50% or better for the minor products 1-butyl nitrate and propene oxide, and to within a factor of 2 for methyl nitrate in propene-containing runs. Propionaldehyde was consistently underpredicted in all runs; it is probably a chamber contaminant. For formaldehyde and acetaldehyde, the major products in both systems, fits to within -420% were often obtained, yet for a number of experiments, significantly greater discrepancies were observed, probably as a result of experimental and/or analytical problems.The good fits to experimental data were attained only after adjusting several rate constants or rate constant ratios related to uncertainties concerning chamber effects or the chemical mechanism. The largest uncertainty concerns the necessity to include in the mechanism a significant rate of radical input from unknown sources in the smog chamber. Other areas where fundamental kinetic and mechanistic data are most needed before a predictive, detailed propene + n-butane-NO,-air smog model can be completely validated concern other chamber effects, the 03 + propene mechanism, decomposition rates of substituted alkoxy radicals, CARTER E T AL.primary quantum yields for radical production as a function of wavelength for aldehyde and ketone photolyses, and the mechanisms and rates of reactions of peroxy radicals with NO and NOz.

show abstract

Stratospheric Ozone: An Introduction to Its Study

Series

1976

1976, Chemistry and Physics of the Stratosphere

View full text Add to dashboard Cite

An analysis is made of the varions re actions in which ozone and atomic oxyge n are involve d in the stratosphère. At the présent time, hydrogen. nitrogen. and chlorine compounds in the ranges parts per million, parts per billion, and parts per I rillion may have significant chemical effects. I n the upper stratosphère, above the ozone peak. where there is no slrong departure from photochemical equilibrium conditions, the action of hydroxyl arid hydroperoxyl radicals of nitrogen dioxide and chlorine monoxide on atomic oxygen and of atomic chlorine on ozone can be introduced. A précise détermination of their ex act effects requires Knowledge of (1) the vertical distribution of the HjO. CH,. and Hj dissociation by reaction of thèse molécules with electronically excited oxygen atom OCf): (2) the ratio of the OH and HOj concentrations and their absolute values, which dépend on insufficiently known rate coefficients: (3) the various origins of nitric oxide production, with their vertical distributions relaled to latitude and season; and (4) the various sources giving différent chlorine compounds lhat may be dissociated in the stratosphère. I n the lower stratosphère, below the ozone peak. there is no important photochemical production of Oj, but there exist various possibilities of transport. The prediclability of the action of chemical reactions dépends strongly on important interactions between OH and HOj radicals with CO and NO. respectively. which affect the ratio n(OH)/n(\\Oi) at the tropopause level; between OH and NOj. which lead to the formation of nitric acid with its downward transport toward the troposphère; between NO and HO2. which lead to NO? and its subséquent photodissociation; between CI O and NO. which also lead to NOj and become more important than the reaction of CI O with O; and between Cl and various molécules, such as CH. and Hj, which lead to HCl with its downward transport toward the troposphère. Ail thèse chemical processes are subjeci to many changes since they occur in the lower stratosphère where seasonal. latiludinal, and even daytoday variations of the ozone concentrations are observed in associa tion with advective and dynamic transports, which dépend on meteorological conditions as indicated by variations of tropopause heights.

show abstract

The Oxidation of Formyl Radicals

Cited by 74 publications

References 0 publications

Unusual H₂‐forming chain reaction in the 3130‐Å photolysis of formaldehyde‐oxygen mixtures at 25°C

Unusual H₂‐forming chain reaction in the 3130‐Å photolysis of formaldehyde‐oxygen mixtures at 25°C

Computer modeling of smog chamber data: Progress in validation of a detailed mechanism for the photooxidation of propene and n‐butane in photochemical smog

Stratospheric Ozone: An Introduction to Its Study

Contact Info

Product

Resources

About

The Oxidation of Formyl Radicals

Cited by 74 publications

References 0 publications

Unusual H2‐forming chain reaction in the 3130‐Å photolysis of formaldehyde‐oxygen mixtures at 25°C

Unusual H2‐forming chain reaction in the 3130‐Å photolysis of formaldehyde‐oxygen mixtures at 25°C

Computer modeling of smog chamber data: Progress in validation of a detailed mechanism for the photooxidation of propene and n‐butane in photochemical smog

Stratospheric Ozone: An Introduction to Its Study

Contact Info

Product

Resources

About

Unusual H₂‐forming chain reaction in the 3130‐Å photolysis of formaldehyde‐oxygen mixtures at 25°C

Unusual H₂‐forming chain reaction in the 3130‐Å photolysis of formaldehyde‐oxygen mixtures at 25°C