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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

2000

Vol. 74, nr 8

1143-1148

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.

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

1999

vol. 73 nr 5

813-820

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.