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Distribution of stable isotopes in the River Sava in Serbia

Miljević N. R., Golobočanin D. D., Nadeždić M. L., Ogrinc N.

Nukleonika

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2008

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Vol. 53, suppl. 2

129--135

EN

Grab water samples were collected from the research ship ‘ARGUS’ at four locations in Serbia, Ostružnica (17 rkm), Šabac (103.6 rkm), Sremska Mitrovica (136.4 rkm), and Jamena (195.0 rkm) from the mid-river, and near the left and right banks during longitudinal survey of the River Sava performed in August 2006. The stable isotope ratios of hydrogen and oxygen (2H/1H and 18O/16O) were determined along with other physicochemical and biological parameters. The δ18O values of river water ranged from −9.2‰ to −8.5‰, and δ2H values ranged from −66‰ to −61‰. Samples taken from the mid-river along the main stem of the Sava at all examined locations appeared to be isotopically the same stream water with a value of −9.0 ± 0.1‰ for δ18O and −65 ± 1.0‰ for δ2H. The results are considered in relation to the isotopic changes known to occur in water subjected to evaporation and mixing.

2

Carbon-13 Isotope Effect for Carbon Dioxide Formation in the Reaction of Liquid Formic Acid with Uranium Trioxide

Zieliński M., Zielińska A., Ogrinc N., Papiernik-Zielińska H., Kobal I.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 6

889-894

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Introduction to Studies of Deuterium Isotope Effects on the Decarboxylation 13C KIE and on the Decarboxylation of the Phenylpropiolic Acid (PPA) in D3PO4/D2O Solution

Zieliński M., Zielińska A., Ogrinc N., Kobal I., Papiernik-Zielińska H.

Polish Journal of Chemistry

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2000

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Vol. 74, nr 12

1743-1749

EN

Carbon-13 kinetic isotope effect (KIE) in the decarboxylation of phenylpropiolic acid (PPA) in 85% D3PO4 in D2O has been studied and compared with the 13C KIE in decarboxylation of PPA in 85% H3PO4 in H2O. The decarboxylation of PPA in 85% D3PO4 in D2O solution proceeds with slower rate than in 85% H3PO4 solution in H2O in agreement with the proposed mechanism of decarboxylation, which involves the protonation of the triple bond of PPA in the rate determining step. The very negligible decarboxylation 13C KIE equal: (k12/k13)D = 1.0006 0.0012 in 85% D3PO4/D2O medium in the 70–90 graduate C interval, corroborates strongly the previous conclusions drawn from (k12/k13) values found in 85% H3PO4 water solutions. Formation of the sp2(C-D) bond in the decarboxylation transition state inD3PO4/D2Osolutions takes place with less steric requirements than the sp2(C–H) bond formation in H3PO4/H2O medium.

4

Carbon-13 Isotope Fractionation in the Decarboxylation of Phenypropiolic Acid in Orthophosphoric Acid and in Diphosphoric Acid

Zieliński M., Ogrinc N., Zielińska A., Koblyuk N., Papiernik-Zielińska H.

Polish Journal of Chemistry

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2000

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Vol. 74, nr 5

707-715

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Carbon-13 isotope effect for decarboxylation of phenylpropiolic acid (PPA) in concentrated phosphoric acids

Zieliński M., Zielińska A., Papiernik-Zielińska H., Ogrinc N., Kobal I.

Nukleonika

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2000

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Vol. 45, nr 2

121-124

EN

13C isotope effects on the decarboxylation of phenylpropiolic acid (PPA) in 93–97% H3PO4 and in 23% diphosphoric acid in orthophosphoric acid have been investigated from 293 to 353 K. The initial 13C fractionations in all three systems are in agreement with the 13C decarboxylation fractionations expected assuming the loss of the one carbon-carbon bond in the transition state. In 100% H3PO4 and in 23% diphosphoric acid in orthophosphoric acid later fractions of carbon dioxide are depleted in carbon-13 to a greater degree than expected, probably due to isotopic preequilibria between stable and decarboxylating forms of PPA. At 353 K and higher temperature strong deviations of the experimental rate constants and of the experimental 13C fractionations from the values extrapolated from lower temperature are observed. A tentative decarboxylation scheme operating in concentrated phosphoric acid media is proposed.

6

Carbon-13 fractionation in the oxidation of propionate of natural isotopic composition with permanganate and manganate

Zieliński M., Fry A., Zielińska A., Ogrinc N., Papiernik-Zielińska H., Kobal I.

Nukleonika

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2000

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Vol. 45, nr 4

221-224

EN

Carbon-13 fractionation in the oxidation of sodium propionate of natural isotopic composition with permanganate in water solution and with manganate in alkaline solution has been investigated and compared with carbon-14 kinetic isotope effects in the oxidation of (3-14C) – and (2-14C) propionate with permanganate. The experimental carbon-13 isotope ratios, R(13C/12C)cumul., corrected for dilution of R(13C/12C)a by carbon dioxide derived from all external sources and by carbon dioxide derived from (C-1) and from (C-3) of propionate at its complete and partial oxidations, used for calculation of 13C alfa KIE, provided the carbon-13 isotope effects corresponding to initial oxidation of alpha carbon, which correlate well with (2-14C) KIE determined previously, (k12/k13 -1)?100 ? 1/2(k12/k14 -1)?100 ? 1/2(4.6š0.3) at 373 K. The possibility of extension of isotope ratio measurements, using modern double collector mass spectrometers, from geochemical, biomedical, agriculture and environmental research to carbon-13 isotope effects studies in chemical organic reactions is briefly discussed.

7

C-13 isotope effects in the decarboxylation of phenylpropiolic acid (PPA) in water solution of formic acid (FA)

Zieliński M., Zielińska A., Ogrinc N., Kobal I., Paul H., Bernasconi S., Papiernik-Zielińska H.

Polish Journal of Chemistry

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1999

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vol. 73 nr 5

813-820

EN

Kinetics and the carbon-13 kinetic isotope effects in the decarboxylation of phenylpropiolic acid in HCOOH/H2O, 1:1/V:V, solution have been examined between 80-140.13oC. 13C KIE in the decarbonylation of formic acid, proceeding with measurable rate in this medium between 130-150oC, has determined also and compared with corresponding values found in the pure HCOOH/H2O solution. Kinetics and C-13 KIE in the decarboxylation of phenylpropiolic acid in pure water have been investigated subsequently between 100-143oC in all glass reaction vessels sealed under vacuum. The enthalpy of activation of decarboxylation of PPA in pure water, 30.20 kcal/mol, and the entropy of activation, DS* = -3.7 e.u., are by 6.7 kcal/mol and 12.5 e.u., respectively, higher than the DH* and DS* values found in the decarboxylation of PPA in pure formic acid. The C-13 KIE equal to 1.004-1.005 between 70-100oC in the pure HCOOH medium increased to C-13 KIE of 1.020 in the case of decarboxylation of PPA at 133.7oC in the initially pure water.