Primary kinetic isotope effects and nature of hydrogen-transfer transition states. Reaction of a series of free radicals with thiols

1971 ◽  
Vol 93 (21) ◽  
pp. 5584-5586 ◽  
Author(s):  
William A. Pryor ◽  
Kenneth G. Kneipp
Keyword(s):  
Free Radicals ◽  
Hydrogen Transfer ◽  
Isotope Effects ◽  
Transition States ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope

Reactive mode composition factor analysis of transition states: the case of coupled electron–proton transfers

2019 ◽  
Vol 21 (45) ◽  
pp. 24912-24918 ◽  
Author(s):  
Mauricio Maldonado-Domínguez ◽  
Daniel Bím ◽  
Radek Fučík ◽  
Roman Čurík ◽  
Martin Srnec
Keyword(s):  
Factor Analysis ◽  
Kinetic Energy ◽  
Isotope Effects ◽  
Transition States ◽  
Kinetic Isotope Effects ◽  
Composition Factor ◽  
Kinetic Isotope ◽  
Proton Transfers ◽  
Relative Kinetic ◽  
Reactive Mode

The kinetic energy distribution in the reactive mode in transition states correlates the asynchronicity of CPET with relative kinetic isotope effects.

Mechanism of the benzidine rearrangement. Kinetic isotope effects and transition states. Evidence for concerted rearrangement

1981 ◽  
Vol 103 (4) ◽  
pp. 955-956 ◽  
Author(s):  
Henry J. Shine ◽  
Henryk Zmuda ◽  
Koon Ha Park ◽  
Harold Kwart ◽  
Ann Gaffney Horgan ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Transition States ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope

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.

Isotope effects in nucleophilic substitution reactions. VII. The effect of ion pairing on the substituent effects on SN2 transition state structure

1989 ◽  
Vol 67 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Zhu-Gen Lai ◽  
Kenneth Charles Westaway
Keyword(s):  
Nucleophilic Substitution ◽  
Isotope Effects ◽  
Transition States ◽  
Substituent Effects ◽  
Ion Pairing ◽  
Kinetic Isotope Effects ◽  
Ion Pair ◽  
Substitution Reactions ◽  
Kinetic Isotope ◽  
Free Ion

The secondary α-deuterium kinetic isotope effects and substituent effect found in the SN2 reactions between a series of para-substituted sodium thiophenoxides and benzyldimethylphenylammonium ion are significantly larger when the reacting nucleophile is a free ion than when it is a solvent-separated ion pair complex. Tighter transition states are found when a poorer nucleophile is used in both the free ion and ion pair reactions. Also, the transition states for all but one substituent are tighter for the reactions with the solvent-separated ion pair complex than with the free ion. Hammett ρ values found by changing the substituent on the nucleophile do not appear to be useful for determining the length of the sulphur–α-carbon bond in the ion pair and free ion transition states. Keywords: Isotope effects, ion pairing, nucleophilic substitution, SN2 reactions, transition states.

Isotope effects in solution: contrasts between muonium and hydrogen in reactions with acetone

1990 ◽  
Vol 68 (10) ◽  
pp. 1719-1724 ◽  
Author(s):  
David C. Walker
Keyword(s):  
Free Radicals ◽  
Physical Properties ◽  
Rate Constants ◽  
Nuclear Physics ◽  
Reaction Rate ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Reaction Rate Constants ◽  
Thiyl Radicals ◽  
Kinetic Isotope

Munonium atoms are hydrogen isotopes with positive muons rather than protons, deuterons, or tritons as nuclei. Thus, they have one ninth the mass of 1H, and microsecond lifetimes. By using nuclear physics counting techniques, muonium can be studied in a wide variety of media and its chemical and physical properties used to appraise hydrogen. Results are described for the interaction of muonium with acetone, showing two types of kinetic isotope effects, formation of free radicals, evidence for intermolecular "muonium bonding", and micelle-induced enhancements of reaction rate constants. Keywords: isotope effects, muonium atoms, muonium bonding, thiyl radicals, micelles.

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