FREE RADICALS BY MASS SPECTROMETRY: XXII. PRIMARY DECOMPOSITION STEPS IN THE MERCURY-PHOTOSENSITIZED DECOMPOSITION OF METHANOL AND DIMETHYL ETHER

The Hg 3P1 photosensitized decomposition of methanol at low pressures proceeds mainly by a dissociation into CH3O radicals and H atoms. No formation of CH2OH radicals is observed. A subsidiary reaction to form CH3 and OH may also be a primary step. Formation of CH2OH radicals at higher pressures is attributed to an abstraction reaction of CH3O with CH3OH.Two primary modes of dissociation are found to occur for dimethyl ether:[Formula: see text]The relative probabilities of occurrence at low pressures are ∼45% and ∼50%, respectively. The possibility that the second reaction proceeds by formation of an excited molecule is discussed.

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FREE RADICALS BY MASS SPECTROMETRY: XXXII. THERMAL DECOMPOSITION OF CYCLOPENTYL RADICALS

Canadian Journal of Chemistry ◽

10.1139/v65-074 ◽

1965 ◽

Vol 43 (3) ◽

pp. 565-569 ◽

Cited By ~ 12

Author(s):

T. F. Palmer ◽

F. P. Lossing

Keyword(s):

Mass Spectrometry ◽

Thermal Decomposition ◽

Free Radicals ◽

Elevated Temperatures ◽

Bond Rupture ◽

Low Pressures

At low pressures and elevated temperatures cyclopentyl radicals are found to dissociate mainly by two modes of reaction: about 34% by loss of H atom to form cyclopentene, and about 66% by a C—C bond rupture to form ethylene and allyl radicals. Under the conditions employed no evidence for a third possible mode, the loss of H2 to form cyclopentenyl radical, could be found. It is estimated that an incidence of 2% of the latter could have been detected.

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Free radicals by mass spectrometry. XL. Primary processes and transient intermediates in the mercury (3P1) photosensitization of hydrazine

Canadian Journal of Chemistry ◽

10.1139/v69-227 ◽

1969 ◽

Vol 47 (8) ◽

pp. 1391-1393 ◽

Cited By ~ 4

Author(s):

A. Jones ◽

F. P. Lossing

Keyword(s):

Mass Spectrometry ◽

Free Radicals ◽

Mass Spectrometer ◽

Direct Evidence ◽

Flow Reactor ◽

Low Pressure ◽

Primary Decomposition ◽

Fast Flow ◽

Transient Intermediates ◽

Fast Flow Reactor

The low pressure mercury (3P1) photosensitized decomposition of hydrazine has been studied at 55 °C in a fast flow reactor coupled to a mass spectrometer. Direct evidence was obtained for the participation of N2H2, N2H3, NH2, and NH in the decomposition, and two primary decomposition modes were established[Formula: see text]

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Free radicals by mass spectrometry. Part II.—The thermal decomposition of ethylene oxide, propyline oxide, dimethyl ether, and dioxane

Discussions of the Faraday Society ◽

10.1039/df9531400034 ◽

1953 ◽

Vol 14 (0) ◽

pp. 34-44 ◽

Cited By ~ 46

Author(s):

F. P. Lossing ◽

K. U. Ingold ◽

A. W. Tickner

Keyword(s):

Mass Spectrometry ◽

Thermal Decomposition ◽

Free Radicals ◽

Ethylene Oxide ◽

Dimethyl Ether

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The combustion of gaseous methyl iodide studied by flash photolysis and kinetic spectroscopy

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1961.0143 ◽

1961 ◽

Vol 263 (1312) ◽

pp. 51-57 ◽

Cited By ~ 12

Keyword(s):

Free Radicals ◽

Gas Phase ◽

Methyl Iodide ◽

Flash Photolysis ◽

Oh Radicals ◽

Methyl Radicals ◽

Kinetic Spectroscopy ◽

Slow Combustion ◽

Low Pressures ◽

Explosive Combustion

The combustion of gaseous methyl iodide has been studied under conditions of slow and explosive combustion and the behaviour of the methyl iodide, the free radicals OH and IO and the products formaldehyde and iodine has been followed by kinetic spectroscopy. At fairly low pressures ( l.0 to 5.5 cm Hg) the behaviour of the methyl iodide and the OH radicals under conditions of slow and explosive combustion indicates that the reaction between methyl radicals and oxygen proceeds by CH 3 + O 2 → H 2 CO + OH. At higher pressures, under slow combustion conditions, formaldehyde is detectable in the gas phase by reaction between methyl radicals and oxygen. Under slow combustion conditions also, the behaviour of the IO radicals and iodine suggests that the iodine atoms produced by the primary photolytic dissociation of m ethyl iodide are temporarily removed in the form of IO radicals, from which the final product iodine is then formed by 2IO → I 2 + O 2 .

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Free radicals by mass spectrometry. XXXVIII. Primary steps in the mercury-photosensitized decompositions of dimethyl sulfide and dimethyldisulfide

Canadian Journal of Chemistry ◽

10.1139/v68-144 ◽

1968 ◽

Vol 46 (6) ◽

pp. 833-839 ◽

Cited By ~ 12

Author(s):

A. Jones ◽

S. Yamashita ◽

F. P. Lossing

Keyword(s):

Mass Spectrometry ◽

Free Radicals ◽

Dimethyl Sulfide ◽

Primary Decomposition

The reaction between mercury (3P1) atoms and dimethylsulfide at 55 °C has been shown to be exclusively[Formula: see text]Two primary modes of dissociation have been established for the corresponding reaction with dimethyldisulfide.[Formula: see text]The former reaction accounts for ~20% of the primary decomposition at 55 °C. No reaction leading to H-atom removal was found for either compound.The subsequent reactions of CH3S and CH3SS radicals, chiefly combination and disproportionation, have been investigated briefly.

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Phenolic constituents and inhibitory effects of the leaf of Rauvolfia vomitoria Afzel on free radicals, cholinergic and monoaminergic enzymes in rat’s brain in vitro

Journal of Basic and Clinical Physiology and Pharmacology ◽

10.1515/jbcpp-2020-0144 ◽

2020 ◽

Vol 0 (0) ◽

Author(s):

Olubukola H. Oyeniran ◽

Adedayo O. Ademiluyi ◽

Ganiyu Oboh

Keyword(s):

Lipid Peroxidation ◽

Free Radicals ◽

Methanolic Extract ◽

Array Detector ◽

Oh Radicals ◽

Inhibitory Effects ◽

Methanolic Extracts ◽

Phenolic Constituents ◽

Rauvolfia Vomitoria

AbstractObjectivesRauvolfia vomitoria is a medicinal plant used traditionally in Africa in the management of several human diseases including psychosis. However, there is inadequate scientific information on the potency of the phenolic constituents of R. vomitoria leaf in the management of neurodegeneration. Therefore, this study characterized the phenolic constituents and investigated the effects of aqueous and methanolic extracts of R. vomitoria leaf on free radicals, Fe2+-induced lipid peroxidation, and critical enzymes linked to neurodegeneration in rat’s brain in vitro.MethodsThe polyphenols were evaluated by characterizing phenolic constituents using high-performance liquid chromatography coupled with diode array detector (HPLC-DAD). The antioxidant properties were assessed through the extracts ability to reduce Fe3+ to Fe2+; inhibit ABTS, DPPH, and OH radicals and Fe2+-induced lipid peroxidation. The effects of the extracts on AChE and MAO were also evaluated.ResultsThe phenolic characterization of R. vomitoria leaf revealed that there were more flavonoids present. Both aqueous and methanolic extracts of R. vomitoria leaf had inhibitory effects with the methanolic extract having higher significant (p≤0.05) free radicals scavenging ability coupled with inhibition of monoamine oxidases. However, there was no significant (p≤0.05) difference obtained in the inhibition of lipid peroxidation and cholinesterases.ConclusionThis study suggests that the rich phenolic constituents of R. vomitoria leaf might contribute to the observed antioxidative and neuroprotective effects. The methanolic extract was more potent than the aqueous extract; therefore, extraction of R. vomitoria leaf with methanol could offer better health-promoting effects in neurodegenerative condition.

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