Purification and Vapor Pressure of Nitric Oxide

Hughes, Ernest E.

doi:10.1063/1.1732104

Cited by 33 publications

(11 citation statements)

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“…The major features of the photolysis of methanethiol with added ethylene may be explained by the reaction sequence CHsS + CzH4 CHaSC2H.j (22) CHsSCzH4 + CHsSH + CHaSCzHb + CHaS (23) CHBSH CHsSCzH4 + zCzH4 _ _ f higher sulfides + CH3S (24) CHsS + R + higher sulfides and dithiaalkanes (25) where R represents any radical, other than CHaS, in the system. A kinetic treatment of the above mechanism, excluding reactions forming sulfides other than CH3SCzHs, yields the expressions In addition to the usual steady-state assumptions, it is also assumed that: (a) the amount of light absorbed by the CH3SH remains constant, independent of the amount of product formed; (b) chain termination steps other than reaction 5 are of minor importance and may be excluded; (c) deactivation of the excited disulfide molecule occurs with unit efficiency and without disproportionation into CH3SH and CHzS and without production of CH, and HS radicals; and (d) the quantum yield of H atoms (or CH3S radicals) in reaction 3 is 1.0.…”

Section: Combination-disproportionation Reactions Of Chasmentioning

confidence: 99%

Reactions of thioyl radicals. IV. Photolysis of methanethiol

Steer¹,

Knight²

1968

J. Phys. Chem.

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The photolysis of methanethiol vapor a t 2537 A in the pressure range 5-800 torr has been studied, and the effect of temperature, light intensity, and of added CF,, CZHO, CzH4, and NO on the rate of formation of products has been determined. For the pure substrate the primary process is S-H bond cleavage, and the primary fragments abstract the sulfhydryl hydrogen of the substrate. The quantum yield of Hz formation, extrapolated to zero pressure, is 1.00 f 0.05. CHSS radicals, formed in either the primary process or as a result of abstractive attack by H atoms or radicals on the substrate, combine to form an excited disulfide molecule.The major condensable product, CHaSSCHs, arises via collisional deactivation of this excited species, which can also sensitize the decomposition G f the substrate to give eventually CH, and HzS, the other major products observed. At low pressures, CHaSSCHa* may decompose directly to CHaSH and CHZS. The observed increase above unit quantum yield in the rate of formation of Hz and CH3SSCH3, with increasing substrate pressure, is ascribed to an additional sequence of reactions involving the CH3S radical catalyzed decomposition of the substrate. With added ethylene the major products are Hz, CH3SSCH3, and CH3SC2H6. Methyl ethyl sulfide is produced in a chain reaction by the attack of CH3S on the olefinic double bond to form the composite radical, followed by H abstraction from CH3SH. With low pressures of added NO, the major products are HP, CH3SSCH8, and CH3SN0, the thionitrite being formed by the scavenging of CH3S radicals.At higher pressures of NO, a slow chain reaction in which Nz and CHPSNO are produced is operative. A kinetic treatment of the proposed mechanism shows qualitative agreement with observed trends in the data.Several rate-constant ratios have been determined.

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Section: Combination-disproportionation Reactions Of Chasmentioning

confidence: 99%

Reactions of thioyl radicals. IV. Photolysis of methanethiol

Steer¹,

Knight²

1968

J. Phys. Chem.

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“…The strong dependence of rate of production of Hz, propylene, and cyclohexene indicates that H-atom scavenging reactions by olefinic products, a well established phenomenon in sensitized alkane decompositions in general (16,17), is occurring to an appreciable extent here. Propylene is the olefin present in largest concentrations and therefore the most important reaction of this type will be The propyl radicals so formed account, via reaction 8, The reaction analogous to [7] with cyclohexene evidently occurs to a lesser extent, while ethylene, the olefin present in smallest concentrations, does not appear to compete successfully for H-atoms, as suggested by the time independence of its quantum yield.…”

Section: Discussionmentioning

confidence: 99%

“…Nitric oxide (Matheson) was pre-purified by the method of Hughes (7) and subsequently fractionated between -161 "C and -196 "C in the vacuum line. The NO for each run was distilled once, immediately prior to use, from -161 'C to remove any traces of NO2 formed in storage.…”

Section: Methodsmentioning

confidence: 99%

Photosensitization by Cd(³P₁) Atoms. II. Gas Phase Decomposition of Cyclohexane

Kalra¹,

Knight²

1972

Can. J. Chem.

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The photodecomposition of cyclohexane sensitized by Cd(3Pl) atoms has been studied in the vapor phase at 355 "C. The primary decomposition gives hydrogen atoms and cyclohexyl radicals. The volatile products of the decomposition are H,, cyclohexene, propylene, ethane, ethylene, methane, propane, butadiene, and methylcyclopentane. Products other than H2 and cyclo-C6Hlo arise from unimolecular reactions of cyclohexyl radicals, the most important such process being the production of propylene and allyl radicals. Hydrogen yields decrease rapidly with time because of H-atom scavenging reactions involving olefinic products. The quantum yield of molecular hydrogen formation at the shortest exposure time examined is 0.53.La photodecomposition du cyclohexane sensibiliske par des atomes de Cd(3Pl ) a kt6 Ctudiee en phase vapeur a 355 'C. La dkomposition initiale donne des atomes d'hydrogene et des radicaux cyclohexyles. Les produits volatils de la d~com~osition sont Hz, le cyclohexene, le propyl&e, I'bthane, ~'~t h~l e n e , le mbthane, le propane, le butadikne et le mbthylcyclopentane. Les produits differents de Hz et du cyclo-C6Hlo proviennent de reactions unimolkulaires a partir des radicaux cyclohexyles; le processus le plus important etant la formation de radicaux propyknes et allyles. Les rendements en hydrogene diminuent rapidement avec le temps par suite des rbactions qui piegent les atomes d'H et qui impliquent des produits olefiniques. Le rendement quantique correspondant a la formation d'hydrogene molbculaire pendant le temps d'exposition examine le plus court est de 0.53.

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“…The nitric oxide used was Matheson C.1' . grade and was purified by the method of Hughes (16). The procedure followed to ensure colnplete mixing of propionaldehyde and nitric oxide was the same as described previo~~sly (14).…”

Section: Methodsmentioning

confidence: 99%

Kinetics and Mechanisms of the Thermal Decomposition of Propionaldehyde: Part Ii. The Reaction in the Presence of Nitric Oxide

Laidler¹,

Eusuf²

1965

Can. J. Chem.

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'I'hc decomposition of propionaldehyde in the presence of various amounts of nitric oxidc has been studied in the temperature range 520-560 OC and a t propionaldehyde pressures from 30 to 300 mm Hg. The reaction is inhibited by sniall amounts of nitric oxide, and larger a~nounts give rise to strong catalysis. The order of the maximally inhibited reaction is 1.5 and the degfee of inhibition decreases with a n increase of propionaldehyde pressure. In the catalyt~c region the order of the overall reaction is 1.25 with respect to propio~~aldehyde, and the relative rate (the ratio of rates in the presence and absence of nitric oxide) is independent of propionaldehyde pressure. The overall rate in the catalytic region call be expressed as IXTRODUCTIOSAlthough a number of investigations have been carried out on the thermal decoinposition of propionaldehyde in the presence of nitric oxide, the ntechanisln of the reaction has been a matter of controversy. Staveley and Hinshelwood (I) investigated the therinal decomposition of propionaldehyde; they found that the reaction was inhibited by small amounts of nitric oxide and that there was catalysis a t high nitric oxide pressures. They suggested that the maximally inhibited reaction was a non-chain lnolecular process. Smith and Hinshel\vood (2) found that both nitric oxide and propylene reduced the rate by the same amount, and also concluded that the maxiinally inhibited reaction was a molecular process. A recent investigation by Szab6 and 3IArta (3,4) showed that the overall order of the reaction in the presence of nitric oxide was three-halves with respect to propionaldehyde and approxi~nately one-half with respect to nitric oxide a t high nitric oxide pressures. These workers attempted to explain the above facts bjr adding the reactions [ii] [ i i ' ]CaHeNO + C?Hj + products CzH5N0 + C?HeNO + products to the scheme of the uninhibited reaction originally suggested by Boyer and Wiclause ( 5 ) . Analysis of the results of Szab6 and iVIArta (3,4) on the basis of their mechanism reveals that ETi -EBi = 2.4 kcal per lnoleand ETL -2E31 = -2.9 kcal per mole. These relationships indicate unreasonably high activation energies for the chain-ending steps, and suggest that the mechanism does not represent the complete picture. Recently Ho (6) studied the therinal decoinposition of different aldehydes in the presence of nitric oxide, propylene, Canadian Journal of Chemistry. Volu~ne 43 (1905) Can. J. Chem. Downloaded from www.nrcresearchpress.com by 54.191.190.102 on 05/10/18For personal use only.

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Purification and Vapor Pressure of Nitric Oxide

Cited by 33 publications

References 2 publications

Reactions of thioyl radicals. IV. Photolysis of methanethiol

Reactions of thioyl radicals. IV. Photolysis of methanethiol

Photosensitization by Cd(³P₁) Atoms. II. Gas Phase Decomposition of Cyclohexane

Kinetics and Mechanisms of the Thermal Decomposition of Propionaldehyde: Part Ii. The Reaction in the Presence of Nitric Oxide

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Purification and Vapor Pressure of Nitric Oxide

Cited by 33 publications

References 2 publications

Reactions of thioyl radicals. IV. Photolysis of methanethiol

Reactions of thioyl radicals. IV. Photolysis of methanethiol

Photosensitization by Cd(3P1) Atoms. II. Gas Phase Decomposition of Cyclohexane

Kinetics and Mechanisms of the Thermal Decomposition of Propionaldehyde: Part Ii. The Reaction in the Presence of Nitric Oxide

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Photosensitization by Cd(³P₁) Atoms. II. Gas Phase Decomposition of Cyclohexane