Reactions of coals with carbon monoxide/deuterium oxide in the presence of alkaline catalysts. Establishment of mineral matter in the coal as the origin of kinetic isotope effects

The kinetics of the reactions of hydrogen peroxide and cyanide with native horseradish peroxidase, as well as reactions of compounds I and II with ferrocyanide have been studied in ordinary water and in deuterium oxide at 25 °C and ionic strength 0.11 using a stopped-flow apparatus. Rate constants for all reactions were measured over a wide range of acidity in both solvents from which equilibrium and kinetic isotope effects were evaluated. Protonation of an ionizable group on the enzyme with a pKa value of 4.15 ± 0.05 in water inhibits the reactions with both hydrogen peroxide and cyanide. A significant kinetic isotope effect, kH/kD = 1.6 ± 0.1, was measured for compound I formation whereas no significant kinetic isotope effect was found for cyanide binding. On the basis of these findings, a partial mechanism for compound I formation is proposed in which the group of pKa 4.15 plays a crucial role. The pH dependencies of the ferrocyanide reaction in the pH interval 4.5–10.8 confirmed the role of an acid group with a pKa of 5.2 for compound I and for compound II a pKa of 8.6 and another with a value lower than that encompassed by the pH range of the study. Equilibrium isotope effects were found but no kinetic isotope effects for either the reaction of compound I or of compound II This suggests that there are no rate-limiting proton transfers in the reactions between ferrocyanide and compounds I and II of horseradish peroxidase. The only reducing substrates which exhibit positive kH/kD values possess a labile proton.

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Spontaneous dissolution of metals in aqueous electrolytes. I. Kinetic isotope effects in the reaction of iron with hydrochloric acid solutions in protium and in deuterium oxide

The Journal of Physical Chemistry ◽

10.1021/j100683a008 ◽

1971 ◽

Vol 75 (14) ◽

pp. 2112-2116 ◽

Cited By ~ 1

Author(s):

I. R. Bellobono ◽

F. Mazza

Keyword(s):

Hydrochloric Acid ◽

Deuterium Oxide ◽

Isotope Effects ◽

Kinetic Isotope Effects ◽

Aqueous Electrolytes ◽

Acid Solutions ◽

Kinetic Isotope ◽

Hydrochloric Acid Solutions

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The thermally induced rearrangements of 2-vinyloxirane

Canadian Journal of Chemistry ◽

10.1139/v76-484 ◽

1976 ◽

Vol 54 (21) ◽

pp. 3364-3376 ◽

Cited By ~ 38

Author(s):

Robert J. Crawford ◽

Stuart B. Lutener ◽

Robert D. Cockcroft

Keyword(s):

Carbon Monoxide ◽

Gas Phase ◽

Isotope Effects ◽

Kinetic Isotope Effects ◽

Thermally Induced ◽

Rate Determining Step ◽

Kinetic Isotope ◽

Carbonyl Ylide ◽

Structural Isomerization ◽

Kinetics Of

The kinetics of the gas phase thermolysis of 2-vinyloxirane (4) have been studied over the temperature range 270–310 °C. The racemization of chiral 4 occurs six times faster than the structural isomerization to 2,3-dihydrofuran, (E)- and (Z)-2-butenal, and 3-butenal. The butenals undergo a slow thermolysis to propene and carbon monoxide. cis-Deuterio- and trans-3-deuterio-vinyloxirane have been synthesized and their interconversion is slow. Deuterium kinetic isotope effects on mono- and dideuterio-4 suggest that for the formation of the butenals the rate determining step involves rupture of the oxirane C—O bond. The dihydrofuran is produced by thermolysis of the oxirane C—C bond. The preferred mechanistic interpretation is that a carbon–oxygen diradical serves as an intermediate for butenal formation, and that a carbonyl-ylide is involved in the formation of the dihydrofuran.The relative rates, at 307.4 °C, of cis–trans-5-isomerization:dihydrofuran formation:racemization: butenal formation for 3-deuterio-2-vinyloxirane are 1.0:0.88:40.2:5.94, respectively.

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