The Reaction of Methyl Radicals With Formaldehyde

Blake, A. R.; Kutschke, K. O.

doi:10.1139/v59-215

Cited by 25 publications

(18 citation statements)

References 12 publications

(8 reference statements)

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“…apart from ethane >> rnetl~ane > ethylene no other significant products were found, in agreement with earlier studies (3,6,8,11).…”

Section: Materials and Experimental Techniquesupporting

confidence: 92%

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Thermal decomposition of di-tert-butyl peroxide at high pressure

Shaw¹,

Pritchard²

1968

Can. J. Chem.

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The thermal decomposition of di-tert-butyl peroxide has been studied in the presence of carbon dioxide at total pressures from 0.05 to 15 at111 and temperatures from 90-130 "C. The first-order rate .constant for the decomposition is independent of total pressure in this range, with Arrhenius parameters E = 37.8 f 0.3 kcal/mole and log A (s-') = 15.8 + 0.2. A reevaluation of previous data on this reaction leads us to recommend E = 37.78k0.06 kcal/mole and log A (s-') = 15.80 F 0.03 over the temperature range 90-350 "C; extension of this range to higher temperatures using a shock tube would be worthwhile.Canadian Journal of Chemistry, 46, 2721 (1968) It has been postulated by Birss (1) and by Bose and Hinshelwood (2) that in the thermal decomposition of di-tert-butyl peroxide (DTBP), a second channel exists between reactants and products which they called induced decomposition. The evidence upon which these arguments are based is in our view not very strong, and we believe that the postulate is unnecessary. It was found that the rate of decomposition at 160 "C increased with pressure between 50 and 600 mm. However, since the explosion limit of the peroxide decomposition is estimated (3) to be around 600 mm at 150 "C, the probable cause of the rise in rate with pressure becomes apparent. It was also found that added gases, namely SF,, CF,, CO,, CCl,, SiF,, and N,O caused an acceleration of the reaction, whereas acetone, 17-hexane, and N2 were without effect. It was recognized later by Archer and Hinshelwood (4) that in the case of CCI,, the acceleration may have been partly a chemical effect involving chloriile atoms. More recently, Flowers, Batt, and Bellson (5) showed that the peroxide decomposition was strongly catalyzed by HC1 by a mechanism involving chlorine atoms, and further evidence for the existence of chlorine atoms in the peroxide/CCl, reaction is available (6). Also, Batt and Cruickshank (7) have shown that CH,F is formed in the peroxide/SF, decomposition. We suggest that all these observed acceleratioils in the presence of CF,, SiF,, CO,, and N,O are due either to chemical reaction of some kind or to the presence of trace quantities of chlorinated impurities; it is reasonable to suppose that the N,, acetone, and hexane used in the above experiments were free from chlorinated impurities. Our own experiments described below show that carefully purified CO, has no effect on the rate of peroxide decomposition up to a pressure of 15 atm, and we believe that the idea of induced decom~osition should not be included in the current theoretical description of unimolecular reactions. Materials and Experimental TechniqueCommercial di-tert-butyl peroxide contains about 0.2% of minor impurities including 0.04% acetone (8); these were removed by preparative scale gas chromatography. Carbon dioxide was made from commercial dry-ice: the gas was condensed onto phosphorus pentoxide it1 vacuo, degassed, and then sublimed into a storage vessel; mass-spectrometer analysis failed to reveal any impurity.Each experiment wa...

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“…apart from ethane >> rnetl~ane > ethylene no other significant products were found, in agreement with earlier studies (3,6,8,11).…”

Section: Materials and Experimental Techniquesupporting

confidence: 92%

“…At small percentage conversions, the rate of formation of acetone can be used as a measure of the rate of decomposition of the peroxide (3,11). Thus, since it was not in general possible to transfer the whole contents of the reaction vessel to the vapor phase chromatographic (v.p.c.)…”

Section: Materials and Experimental Techniquementioning

confidence: 99%

Thermal decomposition of di-tert-butyl peroxide at high pressure

Shaw¹,

Pritchard²

1968

Can. J. Chem.

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“…deter~nined by equation [2] varies with the isobutane pressure, which coilfirnls the earlier observation (1). Unlilce the addition of hydrogen (2), however, the addition of isobutane to acetone-dG did not affect the ratio IIcD1/R&yD6[A] in any way.…”

Section: E X P E R I M E N T a Lsupporting

confidence: 83%

The Reaction Between Methyl Radicals and Isobutane

Blake¹,

Henderson²,

Kutschke³

1961

Can. J. Chem.

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A B S T R A C TI t has been confirmed that the apparent rate constant for the reaction between methyl radicals, produced by the photolysis of deuterated acetone, and isobutane increases with decreasing isobutane pressure. A n explanation is proposed to account for this observation suggesting that the production of methane by disproportionation between methyl and t-butyl radicals was not negligible as has been assumed previously. I N T R O D U C T I O NObservations made recently in this laboratory indicated that values of the apparent rate constants for the abstraction of hydrogen by methyl radicals, calculated using conventional methods, depended on the pressure of the added hydrogen donor. The reaction of methyl radicals with isobutane using the pyrolysis of di-t-butyl peroxide a s a source of methyl radicals is an exanlple of such a system (I). When mixtures of deuterated acetone and hydrogen were photolyzed, the rate constant for the reaction of methyl radicals with hydrogen was found to be a function of the hydrogen pressure (2). In view of the apparent similarities between the two systems, an investigation of the photolysis of deuterated acetone -isobutane ~llixtures was made. E X P E R I M E N T A LThe apparatus and methods of analysis were similar to those employed in the photolysis of the deuterated acetone -hydrogen mixtures (2, 3). The deuterated acetone consisted of 98.2% acetone-ds and 1.8% acetone-d5. Phillips Research Grade isobutane was outgassed by bulb-to-bulb distillations a t -160" C. The temperature of the reaction cell was 471% 0.5" K for all experiments. R E S U L T S A N D DISCUSSIONIn the photolysis of mixtures of deuterated acetone and isobutane, it is usually assumed that methane and ethane are formed b y the following reactions:When the deuterated acetone was photolyzed alone ( 2 ) , small amounts of CD3H were formed due to the presence of acetone-d5 in the sample, and its yield was given bywhere [ A ] is the acetone concentration in molecules/cc. Allowance for this CDjH was made when calculating values of k,/kalt2.

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“…Multiplying, one obtains Ic,k,,,-1i2, the quotient determined at lower temperatures in previous work (4,5).…”

mentioning

confidence: 91%

“…Including literature data from 357-1005 K, the Arrhenius plot for this quotient is a curve. The reaction of methyl radicals with formaldehyde [9] CH, + CHzO -+ CH, + CHO has one of the smallest activation energies known for The radicals formed in reactions 3, and decomtransfer Of a from a atom to pose rapidly to form CH,O; the radical formed in a methyl radical (1) Recent experiments, using CH, reaction decomposes to form CO. and CH2O generated in the P Y~~~Y~~~ Of diMaking the steady-stafe assumption for each ether at to 1223 (2) and loo' (3)7 radical, assuming long chains and integrating the have indicated that the reaction is faster at these rate equations for product formation, tile following temperatures than predicted from Arrhenius parameters determined at 357-435 K (4,5 actions, have been omitted. The assumptions will be reconsidered in the Discussion.…”

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confidence: 99%