Hydrolysis of Phosphotriesters:  Determination of Transition States in Parallel Reactions by Heavy-Atom Isotope Effects

2001 ◽  
Vol 123 (38) ◽  
pp. 9246-9253 ◽  
Author(s):  
Mark A. Anderson ◽  
Hyunbo Shim ◽  
Frank M. Raushel ◽  
W. W. Cleland
Keyword(s):  
Isotope Effects ◽  
Heavy Atom ◽  
Transition States ◽  
Parallel Reactions ◽  
Hydrolysis Of

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.

Understanding the transition states of phosphodiester bond cleavage: Insights from heavy atom isotope effects

Biopolymers ◽  
2003 ◽  
Vol 73 (1) ◽  
pp. 110-129 ◽  
Author(s):  
Adam G. Cassano ◽  
Vernon E. Anderson ◽  
Michael E. Harris
Keyword(s):  
Bond Cleavage ◽  
Isotope Effects ◽  
Heavy Atom ◽  
Transition States ◽  
Phosphodiester Bond

Probing transition states of concerted rearrangements for synchronicity: Use of heavy-atom kinetic isotope effects

1986 ◽  
Vol 138 (1-2) ◽  
pp. 107-112
Author(s):  
Henry J. Shine ◽  
Lidia Kupczyk-Subotkowska ◽  
Witold Subotkowski ◽  
Ewa Gruszecka
Keyword(s):  
Isotope Effects ◽  
Heavy Atom ◽  
Transition States ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope

scholarly journals An investigation into the butyrylcholinesterase-catalyzed hydrolysis of formylthiocholine using heavy atom kinetic isotope effects

2016 ◽  
Vol 65 ◽  
pp. 57-60 ◽  
Author(s):  
Emily J. Fogle ◽  
John F. Marlier ◽  
Anthony Stillman ◽  
Xin Gao ◽  
Yashas Rao ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Heavy Atom ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Hydrolysis Of

The hydrolysis of substituted benzyl nitrates in water. II. Effect of ortho-substitution

1976 ◽  
Vol 54 (22) ◽  
pp. 3614-3619 ◽  
Author(s):  
Kalavelil Matthew Koshy ◽  
Ross Elmore Robertson ◽  
George Stanley Dyson ◽  
Surendra Singh
Keyword(s):  
Transition State ◽  
Isotope Effects ◽  
Mixed Solvents ◽  
Product Formation ◽  
Internal Factors ◽  
Methyl Substitution ◽  
Reaction Rule ◽  
Deuterium Isotope Effects ◽  
Hydrolysis Of

The relative effects of methyl substitution on the rates of hydrolysis of benzyl nitrates in water showed but small differences from earlier reports involving the displacement of Cl− in mixed solvents. The values of the α-deuterium isotope effects for the hydrolysis of the 2,4- and 2,6-dimethyl homologs were similar to that for the p-methylbenzyl nitrate suggesting an approach to limiting hybridization in each case. In spite of this similarity, there was a large negative shift in the value of ΔCP≠ for the hydrolysis of the 2,6-dimethylbenzyl nitrate compared to the values for the 2-methyl and 4-methyl members of the series. The value of ΔCP≠ for the 3-methyl was about the same as for the unsubstituted member. The mechanistic implications of these results while in agreement with the Swain–Thornton reaction rule emphasize the importance of external as well as internal factors in the determination of charge development and separation at the transition state. Steric hindrance or charge dispersal in the cation, or both, in limiting the rate of product formation, delay the attainment of the transition state and hence favor more negative values of ΔCP≠.

DETERMINATION OF MICRO-AMOUNTS OF 5β-PREGNAN-3α-OL-20-ONE IN URINE USING INFRARED-SPECTROMETRY

1962 ◽  
Vol 41 (2) ◽  
pp. 234-246 ◽  
Author(s):  
H. J. van der Molen
Keyword(s):  
Infrared Spectrum ◽  
Quantitative Determination ◽  
Acid Hydrolysis ◽  
Chromatographic Separation ◽  
Pure Form ◽  
Infrared Spectrometry ◽  
Hydrolysis Of

ABSTRACT A procedure for the quantitative determination of 5β-pregnan-3α-ol-20-one in urine is described. After acid hydrolysis of the pregnanolone-conjugates in urine, the free steroids are extracted with toluene. Pregnanolone is isolated in a pure form as its acetate; after chromatographic separation of the free steroids on alumina, the fraction containing pregnanolone is acetylated and rechromatographed on alumina. Quantitative determination of the isolated pregnanolone-acetate is carried out with the aid of the infrared spectrum recorded by a micro KBr-wafermethod. The reliability of the method under various conditions is discussed under the headings, specificity, accuracy, precision and sensitivity. It is possible to determine 30–40 μg pregnanolone in a 24-hours urine portion with a precision of 25%.

Sign in / Sign up

Export Citation Format

Share Document