Chemiluminescence from the reactions of ozone with sulphur compounds

1984 ◽  
Vol 62 (3) ◽  
pp. 417-423 ◽  
Author(s):  
P. K. Arora ◽  
J. P. S. Chatha
Keyword(s):  
Gas Phase ◽  
Singlet State ◽  
Carbon Disulphide ◽  
Emission Spectra ◽  
Reaction Pathways ◽  
Ozone Molecule ◽  
Dimethyl Sulphide ◽  
Sulphur Compounds ◽  
Remarkable Similarity ◽  
Dimethyl Disulphide

Emissions from excited SO2 in its singlet state (1B1, and/or 1A2) and triplet state (3B1) have been observed in gas-phase chemiluminescent reactions of ozone with a number of sulphur compounds. The compounds studied are carbon disulphide, thiophene, diallyl sulphide, diallyl disulphide, dimethyl sulphide, dimethyl disulphide, and thiophenol. The reaction pathways responsible for the formation of excited molecules are discussed. The remarkable similarity between the emission spectra of the reactions and the chemiluminescence from the SO + O3 reaction confirms that SO is a precursor for the observed chemiluminescence. Disulphides are found to be more chemiluminescent than monosulphides. The absence of chemiluminescence from HCHO* in the reactions of ozone with allyl sulphide and disulphide indicates that the attack of ozone molecule is on the C—S bond in organic sulphides.

Quantum yields in the photolytic oxidation of some sulphur compounds

1981 ◽  
Vol 59 (18) ◽  
pp. 2750-2754 ◽  
Author(s):  
D. F. Sheraton ◽  
F. E. Murray
Keyword(s):  
Quantum Yield ◽  
Atmospheric Pressure ◽  
Photon Absorption ◽  
Quantum Yields ◽  
Methyl Mercaptan ◽  
Dimethyl Sulphide ◽  
Sulphur Compounds ◽  
Photo Oxidation ◽  
Dimethyl Disulphide ◽  
Oxidation In Air

The photolytic oxidation of methyl mercaptan, dimethyl sulphide, and dimethyl disulphide was studied in a batch photolysis apparatus. Short wavelength ultraviolet light was provided by a deuterium discharge lamp and monitored by a monochromator equipped with an extended response photomultiplyer tube. Sulphide concentrations were determined using a gas chromatograph equipped with a flame photometric detector having a sulphur response at 365 nm.The rate of photo-oxidation of methyl mercaptan was found to be a linear function of the photon absorption rate and exhibited a quantum yield of 12. The methyl mercaptan photo-oxidation rate was found to be unaffected by increased oxygen concentration, decreased atmospheric pressure, or the presence of sulphur dioxide.The quantum yield of dimethyl sulphide photo-oxidation was found to be dependent upon air pressure; the quantum yield of 4 at 1 atm pressure increased to 8 at 1/4 atm.The quantum yield of dimethyl disulphide photo-oxidation in air was found to be 1.9 at atmospheric pressure and a disulphide concentration of 7.04 × 10−5M.

Flavour sulphides are produced from methionine by two different pathways by Geotrichum candidum

2000 ◽  
Vol 67 (3) ◽  
pp. 371-380 ◽  
Author(s):  
YANN DEMARIGNY ◽  
CÉLINE BERGER ◽  
NATHALIE DESMASURES ◽  
MICHELINE GUEGUEN ◽  
HENRY E. SPINNLER
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Geotrichum Candidum ◽  
Gas Chromatography Mass Spectrometry ◽  
Specific Production ◽  
Dimethyl Sulphide ◽  
Sulphur Compounds ◽  
Nitrobenzoic Acid ◽  
Dimethyl Disulphide ◽  
Chromatography Mass Spectrometry

We have investigated the capacities of Geotrichum candidum strains to produce sulphides from methionine. This attribute is very important in cheese technology because of the flavouring potential of sulphur compounds. A spectrophotometric procedure using 5,5′-dithiobis(2-nitrobenzoic acid) to determine sulphides was tested on a collection of G. candidum strains, and confirmed by gas chromatography–mass spectrometry. The strains were distinguished on the basis of their ability to produce methanethiol. Gas chromatography–mass spectrometry also made it possible to identify other sulphides, such as dimethyl disulphide, dimethyl trisulphide and dimethyl sulphide. Using sonicated cells, the specific production of these four sulphides was studied in presence of L-[S-methyl-2H]methionine. Both methanethiol and dimethyl sulphide were produced from methionine, but two different pathways were used by G. candidum.

The production of sulphur compounds in Cheddar cheese and their significance in flavour development

1976 ◽  
Vol 43 (2) ◽  
pp. 313-320 ◽  
Author(s):  
D. J. Manning ◽  
Helen R. Chapman ◽  
Zena D. Hosking
Keyword(s):  
Cheddar Cheese ◽  
Dimethyl Sulphide ◽  
Gas Chromatograph ◽  
Sulphur Compounds ◽  
Cheese Flavour ◽  
Photometric Detector

SummaryA method is described for determining H2S, methanethiol and dimethyl sulphide in Cheddar-cheese headspace. Cheeses ranging in age from 2 to 12 months were analysed using a gas chromatograph equipped with a photometric detector. These cheeses were presented to a trained flavour panel for the assessment of quality and intensity of Cheddar cheese flavour.An attempt is made to correlate the concentration of sulphur compounds in the headspace with the average flavour scores. The results suggest that the flavour intensity of the cheese is related to the concentration of methanethiol in the headspace.

Laser excitation and emission spectra of the hexafluorobenzene cation in the gas phase

1981 ◽  
Vol 103 (2) ◽  
pp. 326-329 ◽  
Author(s):  
Trevor Sears ◽  
Terry A. Miller ◽  
V. E. Bondybey
Keyword(s):  
Gas Phase ◽  
Laser Excitation ◽  
Emission Spectra

The gas-phase photochemistry and thermal decomposition of glyoxylic acid

1985 ◽  
Vol 63 (2) ◽  
pp. 542-548 ◽  
Author(s):  
R. A. Back ◽  
S. Yamamoto
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Absorption Spectrum ◽  
Gas Phase ◽  
Singlet State ◽  
Glyoxylic Acid ◽  
Static System ◽  
First Order ◽  
Increasing Temperature ◽  
Homogeneous Formation

The photolysis of glyoxylic acid vapour has been studied at five wavelengths, 382, 366, 346, 275, and 239 nm, and pressures from about 1 to 6 Torr, at a temperature of 355 K. Major products were CO2 and CH2O, initially formed in almost equal amounts, while minor products were CO and H2. Except at 382 nm, the system was complicated by the rapid secondary photolysis of CH2O. Three primary processes are suggested, each involving internal H-atom transfer followed by dissociation.The absorption spectrum is reported and shows the three distinct absorption systems. A finely-structured spectrum from about 320 to 400 nm is attributed to a transition to the first excited π* ← n+ singlet state; a more diffuse absorption ranging from about 290 nm to a maximum at 239 nm is assigned to the π* ← n− state, while a much stronger absorption beginning below 230 nm is attributed to the π* ← π transition. Product ratios vary with wavelength and depend on which excited state is involved.The thermal decomposition was studied briefly in a static system at temperatures from 470 to 710 K and pressures from 0.4 to 8 Torr. Major products were again CO2 and CH2O, but the latter was always less than stoichiometric. First-order rate constants for the apparently homogeneous formation of CO2 are described by Arrhenius parameters log A (s−1) = 7.80 and E = 30.8 kcal/mol. Carbon monoxide and H2 were minor products, and the CO/CO2 ratio increased with increasing temperature and showed some surface enhancement at lower temperatures. The SF6-sensitized thermal decomposition of glyoxylic acid, induced by a pulsed CO2 laser, was briefly studied, with temperatures estimated to be in the 1100–1600 K range, and the CO/CO2 ratio increased with increasing temperature, continuing the trend observed in the static system.

Influence of pH on the Absorption and Fluorescence Spectra of 6,7-Dihydroxycoumarin in Aqueous Solution

1982 ◽  
Vol 37 (3) ◽  
pp. 262-265 ◽  
Author(s):  
Jerzy Grzywacz ◽  
Stanisława Taszner
Keyword(s):  
Aqueous Solution ◽  
Fluorescence Spectra ◽  
Singlet State ◽  
Ph Value ◽  
Emission Spectra ◽  
Excited Singlet ◽  
Acid Base ◽  
Wide Ph Range ◽  
Ph Range ◽  
Influence Of Ph

Abstract Absorption and emission spectra of 6,7-dihydroxycoumarin [6,7-DHC] in aqueous solution over a wide pH range are reported. The absorption spectra proved to be strongly sensitive to the pH-value of the solution, whereas the emission spectra change in this range only insignificantly. An interpretation is attempted on the basis of the differences of the acid-base properties of the 6,7-DHC molecule in its ground and excited singlet state. For this purpose the pKa's and pKax's values have been calculated. It has been stated that in the excited state the phototautomer form is very unlikely.

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