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Solvent Deuterium Isotope Effect in the Acid Catalyzed Decarboxylation of Phenylpropiolic Acid in 85 % D3PO4 in D2O

Zieliński M., Zielińska A., Papiernik-Zielińska H.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 2

211-219

EN

A comparative study of the solvent deuterium isotope effect in the decarboxylation of phenylpropiolic acid (PPA) in 85% perdeuteriated orthophosphoric acid, D3PO4/D2O, has been carried out and the ratio of the decarboxylation rate constants, k(H2O)/k(D2O) equal 1.88š0.07, interpreted as caused by different dissociation constants, Kh/Kd, of normal and perdeuteriated phosphoric acids in H2O and in D2O respectively, and by the deuterium discriminations in the subsequent steps of hydrogen transfer from the solvent H3O+/D3O+ to triple bond of PPAand finally by proton transfer from _-complex to nearest C_-carbon and sp2(C_-H) covalent bond formation. The detachment of carbon dioxide from PPA(decarboxylation step) is the fast process taking place or directly after the rate determining T.S. formation or stepwise by hydration of the vinyl cation and formation of the benzoylacetic acid intermediate compound, which then decarboxylates in the kinetically insignificant step. The discussion is supplemented by calculating the k(H2O)/k(D2O) ratios for decarboxylation scheme involving protonation of the triple bond in the rate determining step and for the reaction scheme involving fast isotope equilibrium between protonated water and protonated triple bond, followed by the rate determining transfer of proton from _-complex to the usual sp2 (C-H) covalent bond. Agood agreement between experimental solvent D2O I.E. and values calculated for reaction scheme involving proton transfer in the r.d.s. (what follows also from the 13CK.I.E. determinations in decarboxylation of PPAinH3PO4/H2OandD3PO4/D2Osolvents) was found.

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Comments on teh Isotopic and Chemical studies of the Thermal Decomposition of Ammonium Nitrate

Zieliński M., Zielińska A., Papiernik-Zielińska H.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 10

1519-1524

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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.

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Carbon-13 Kinetic Isotope Effect for the Decarbonylation of Liquid Formic Acid Assisted with Uranium Trioxide, Uranium Peroxide and Uranyl Formate

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

Polish Journal of Chemistry

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2000

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Vol. 74, nr 10

1427-1427

EN

13C KIE’s in the decarbonylation of liquid formic acid (FA) in the presence of uranium trioxide, UO3, uranium peroxide, UO4, and in the presence of uranyl formate, UO2(HCOO)2, produced in the reaction of the above two uranium oxides with FA have been investigated between 90–120°C. Decarbonylation of HCOOH assisted with uranium trioxide proceeds with normal 13C KIE, expected assuming that 13C–16O bond is broken in the transition state, (k12/k13) KIE = 1.0496/at 100°C. The decarbonylation of liquid formic acid in the presence of uranium peroxide and uranyl formate is accompanied with 13C KIE of intermediate value, which is higher than the 13C KIE observed in the decarbonylation of pure FA, but smaller than the maximum 13C KIE expected for complete rupture of the single carbon–oxygen bond in the decarbonylation T.S. of the protonated formic acid. A mechanism of decomposition of formic acid in the presence of uranium oxides is proposed.

6

Carbon-13 Isotope Fractionation in the decarboxylation of Phenylpropiolic Acid (PPA) Below and Above Its melting Point and in the Decarboxylation of PPA in Phenylacetylene Medium

Zieliński M., Zielińska A., Papiernik-Zielińska H.

Polish Journal of Chemistry

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2000

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Vol. 74, nr 8

1143-1148

EN

C-13 isitipe fractionation in the decarboxylation of pure phenylpropiolic acid (PPA) below and above its melting point and the decarboxylation of PPA in phenylacetylene solutions has been investigated in sealed under vacuum reaction vessels.

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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.

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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.

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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.

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(13)C kinetic isotope effects in the decarboxylation of phenylpropiolic acid (PPA) assisted with formic acid and (13)C KIE in the decarbonylation of formic acid in the presence of PPA

Zieliński M., Zielińska A., Paul H., Papiernik-Zielińska H.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 12

2551-2555

EN

Carbon-13 kinetic isotope effects, (13)C-KIE, in the decarboxylation of phenylpropiolic acid (carboxyl C-13) in formic acid medium and (13)C KIE in the decarbonylation of liquid formic acid assisted with PPA and acetophenone have been studied in the 70-100 degree C temperature interval. The kinetic and isotope results have been discussed and interpreted as indicating that the formation of C alpha-H bond, preceded by the protonation of acetylenic bond of PPA, is the rate determining step followed by carbon dioxide splitting. The (13)CO-KIE in the carbon monoxide generation assisted with PPA is much larger than the (13)CO-KIE observed in the generation of CO in the presence of phenylacetylene. Thus the decaeboxylation of PPA and decarbonylation of formic acid are interrelated processes proceeding in the reaction cage.

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Carbon-13 isotope effects in the decarbonylation of liquid formic acid in the presence of pyrophosphoric acid II. (sup 13)C KIE in the decarbonylation of HCOOH in the presence of H4P2O7

Zieliński M., Zielińska A., Paul H., Papiernik-Zielińska H.

Nukleonika

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1998

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Vol. 43, nr 1

49-56

EN

Carbon-13 isotope fractionation in the decomposition of liquid formic acid of natural isotopic composition in the presence of pyrophosphoric acid has been studied in the temperature range 20-70°C. The initial fractionation of (sup 13)C in the decarbonylation of formic acid catalyzed by dehydrating species depends on the initial ratio of the substrate-formic acid to the dehydrating pyrophosphoric acid introduced into the reaction vessel. The (sup 13)CO fractionation increases with reaction time from the lowest value, which is close to that (sup 13)C KIE expected for the (sup13)C-(sup 1)H bond rupture in the rate determining step, to the highest boundary values observed in the thermal decomposition of pure liquid formic acid and approaching gradually the values of (sup 13)C KIE expected for the (sup 13)C-(sup 16)OH bond splitting in the rate determining step. The observed time and temperature dependences of the (sup 13)C fractionation are explained by the dependence of the (sup 13)C fractionation in catalysed dehydration of F.A. on the degree of solvation of dehydrating species with water molecules derived from the decomposing formic acid.

PL

Przeprowadzono trzy serie doświadczeń mających na celu wyznaczenie zależnego od czasu i temperatury efektu izotopowego 13C w reakcji dekarbonylacji kwasu mrówkowego zachodzącej w obecności kwasu pirofosforowego. Wyjaśniono, że początkowe wartości stosunku k12/k13 wyznaczone na podstawie składu izotopowego (tj. stosunków izotopowych 13C/12C) pierwszych porcji tlenku węgla zbieranych w toku dekarbonylacji HCOOH, określonego na spektrometrach masowych FINNIGAN i FISONS OPTIMA, są zbliżone do współczynników rozfrakcjonowania 13C w reakcjach, w których rozerwanie wiązania 13C-1H zachodzi w etapie krytycznym reakcji chemicznej. Te początkowe dolne wartości k12/k13 wzrastają w toku dalszej dekarbonylacji kwasu mrówkowego do wartości efektu kinetycznego 13C obserwowanego w reakcji rozpadutermicznego czystego kwasu mrówkowego w fazie ciekłej. Wyjaśniono, że systematyczny spadek stałej szybkości reakcji dekarbonylacji w miarę jej postępu i regularny wzrost efektu izotopowego13C jest spowodowany zmianą stopnia solwatacji/uwodnienia cząsteczek kwasu fosforowego i zmianą ich struktury. Uwodnione cząsteczki kwasu ortofosforowego, powstające z rozpadu kwasu pirofosforowego w toku dehydratacji HCOOH nie wpływają w sposów znaczący na efekt kinetyczny 13C w badanej reakcji.

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A contribution to studies of carbon-13 kinetic isotope effect of the decarbonylation of liquid formic acid in the presence of phosphoric acids I. (sup 13)C KIE in the decarbonylation of HCOOH in the presence of phosphoric acids and P2O5

Zieliński M., Zielińska A., Papiernik-Zielińska H.

Nukleonika

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1998

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Vol. 43, nr 1

41-48

EN

A brief review of earlier (sup 13)C KIE studies of the decarbonylation of liquid formic acid (F.A.) and supplementary data concerning the (sup 13)C fractionation observed in the decomposition of this acid in the presence of inorganic dehydrating phosphoric acids and phosphoric anhydride are presented and discussed. The previous ad hoc interpretations of the experimental results are supported by more extensive numerical calculations relating to the cumulative (sup 13)C fractionation found in the carbon monoxide production in the presence of orthophosphoric acid, pyrophosphoric acid and P2O5 in liquid F.A. The full paper is given in the four internally related parts.

PL

Zbadano efekt kinetyczny (sup 13)C w reakcji dekarbonylacji ciekłego kwasu mrówkowego o naturalnym składzie izotopowym, zachodzącej w obecności 85% kwasu ortofosforowego, w obecności kwasu pirofosforowego oraz w obecności czystego bezwodnika kwasu fosforowego i P2O5 uwodnionego częściowo 85% kwasem ortofosforowym. Wyniki doświadczalnych oznaczeń (sup 13)C KlE przedstawionych w trzech pierwszych częściach poddano szczegółowej analizie teoretycznej w części czwartej pracy.