Kinetic isotope effects and aliphatic diazo-compounds. Part III. Solvent isotope effects for 3-diazobutan-2-one and ethyl diazopropionate

1972 ◽  
pp. 2190 ◽  
Author(s):  
W. J. Albery ◽  
A. N. Campbell-Crawford
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Diazo Compounds ◽  
Kinetic Isotope ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

Heavy Atom Kinetic Isotope Effects in HCN Elimination from Some Tricyanides in Methanol [1]

1978 ◽  
Vol 33 (12) ◽  
pp. 1496-1502
Author(s):  
Fouad M. Fouad ◽  
Patrick G. Farrell
Keyword(s):  
Transition State ◽  
Opposite Direction ◽  
Isotope Effects ◽  
Heavy Atom ◽  
Transition States ◽  
Kinetic Isotope Effects ◽  
The Other ◽  
Kinetic Isotope ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

AbstractRates of HCN elimination from polycyanides N,N-dimethyl-4-(1,2,2-tricyanoethyl)-aniline (1), 9-cyano-9-dicyanomethyl fluorene (2), 1,1-diphenyl-1,2,2-tricyanoethane (3), and 2-phenyl-1,1,2-tricyanopropane (4) have been studied in methanol. Elimination from 1 occurs via (E 1 c B)R, mechanism. On the other hand olefin formation from 2-4 has been shown to occur via (E 1)anion pathway. Heavy atom kinetic isotope effects indicated that product stability is not the sole factor controlling the transition state geometries. Values of k12/k14 were found to be in the order 2 > 3 > 4 > 1 which implied transition states with more carbanion-like structure in the opposite direction. Solvent isotope effects and enthalpies of activation were also determined and discussed in terms of transition states geometries.

Mechanism of decarboxylation of substituted anthranilic acids at high acidity

1970 ◽  
Vol 48 (21) ◽  
pp. 3349-3353 ◽  
Author(s):  
G. E. Dunn ◽  
S. K. Dayal
Keyword(s):  
Sulfuric Acid ◽  
Anthranilic Acid ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Carboxyl Group ◽  
Kinetic Isotope ◽  
Anthranilic Acids ◽  
Ph Range ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

The rates of decarboxylation of 4-methyl-, 4-methoxy-, and unsubstituted anthranilic acids have been determined in aqueous buffers over the pH range 2.5–3.8. Electron-releasing substituents increase the rates of ring-protonation about equally for an acid and its anion, and decrease the ratio of decarboxylation to deprotonation of the protonated acid. Rates, 13C-carboxyl kinetic isotope effects, and deuterium solvent isotope effects have been determined for the decarboxylation of anthranilic acid in aqueous sulfuric acid up to 10 M. No evidence for decarboxylation by cleavage of the unionized carboxyl group was obtained.

ChemInform Abstract: KINETIC ISOTOPE EFFECTS AND ALIPHATIC DIAZO-COMPOUNDS. PART VII. THE DECOMPOSITION OF DIAZOMALONATE IONS

1976 ◽  
Vol 7 (21) ◽  
pp. no-no
Author(s):  
W. JOHN ALBERY ◽  
CHRISTOPHER W. CONWAY ◽  
JOHN A. HALL
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Diazo Compounds ◽  
Kinetic Isotope

Kinetic isotope effects and aliphatic diazo-compounds. Part VII. The decomposition of diazomalonato ions

1976 ◽  
pp. 473 ◽  
Author(s):  
W. John Albery ◽  
Christopher W. Conway ◽  
John A. Hall
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Diazo Compounds ◽  
Kinetic Isotope

scholarly journals Inverse Solvent Isotope Effects in Enzyme-Catalyzed Reactions

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1933
Author(s):  
Patrick L. Fernandez ◽  
Andrew S. Murkin
Keyword(s):  
Isotope Effect ◽  
Isotope Effects ◽  
Solvent Isotope Effect ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions ◽  
Solvent Isotope ◽  
Rate Limiting ◽  
Solvent Isotope Effects

Solvent isotope effects have long been used as a mechanistic tool for determining enzyme mechanisms. Most commonly, macroscopic rate constants such as kcat and kcat/Km are found to decrease when the reaction is performed in D2O for a variety of reasons including the transfer of protons. Under certain circumstances, these constants are found to increase, in what is termed an inverse solvent kinetic isotope effect (SKIE), which can be a diagnostic mechanistic feature. Generally, these phenomena can be attributed to an inverse solvent equilibrium isotope effect on a rapid equilibrium preceding the rate-limiting step(s). This review surveys inverse SKIEs in enzyme-catalyzed reactions by assessing their underlying origins in common mechanistic themes. Case studies for each category are presented, and the mechanistic implications are put into context. It is hoped that readers may find the illustrative examples valuable in planning and interpreting solvent isotope effect experiments.

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