Kinetic isotope effect of the 16O + 36O2 and 18O + 32O2 isotope exchange reactions: Dominant role of reactive resonances revealed by an accurate time-dependent quantum wavepacket study

Isotopic vibrational frequencies and the corresponding partition-function ratios for several compounds containing Ge70 and Ge76 have been calculated at various temperatures. The theoretical equilibrium constants for germanium isotope-exchange reactions derived from these partition-function ratios indicate that noticeable germanium isotope fractionation might be effected with laboratory reactions. Calculated kinetic isotope effects in the breaking of diatomic bonds also predict observable alterations of the Ge70/Ge76 ratio.A kinetic isotope effect of 1.0% observed in the chemical reduction of GeO2 to GeO is discussed.

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Kinetic isotope effect in hydrogen isotope exchange between water and phosphines

Journal of Radioanalytical and Nuclear Chemistry ◽

10.1007/bf02387486 ◽

1998 ◽

Vol 230 (1-2) ◽

pp. 303-305

Author(s):

A. Wawer ◽

J. Szyd⊚owski

Keyword(s):

Isotope Effect ◽

Hydrogen Isotope ◽

Isotope Exchange ◽

Kinetic Isotope Effect ◽

Hydrogen Isotope Exchange ◽

Kinetic Isotope

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Strong inverse kinetic isotope effect observed in ammonia charge exchange reactions

Nature Communications ◽

10.1038/s41467-019-13976-8 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 6

Author(s):

L. S. Petralia ◽

A. Tsikritea ◽

J. Loreau ◽

T. P. Softley ◽

B. R. Heazlewood

Keyword(s):

Isotope Effect ◽

Potential Energy Surfaces ◽

Kinetic Isotope Effect ◽

Valuable Insight ◽

Isotopic Substitution ◽

Exchange Reactions ◽

Kinetic Isotope ◽

Reaction Complex ◽

Energy Surfaces ◽

Insight Into

AbstractIsotopic substitution has long been used to understand the detailed mechanisms of chemical reactions; normally the substitution of hydrogen by deuterium leads to a slower reaction. Here, we report our findings on the charge transfer collisions of cold $${{\rm{Xe}}}^{+}$$Xe+ ions and two isotopologues of ammonia, $${{\rm{NH}}}_{3}$$NH3 and $${{\rm{ND}}}_{3}$$ND3. Deuterated ammonia is found to react more than three times faster than hydrogenated ammonia. Classical capture models are unable to account for this pronounced inverse kinetic isotope effect. Moreover, detailed ab initio calculations cannot identify any (energetically accessible) crossing points between the reactant and product potential energy surfaces, indicating that electron transfer is likely to be slow. The higher reactivity of $${{\rm{ND}}}_{3}$$ND3 is attributed to the greater density of states (and therefore lifetime) of the deuterated reaction complex compared to the hydrogenated system. Our observations could provide valuable insight into possible mechanisms contributing to deuterium fractionation in the interstellar medium.

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Kinetic Isotope Effect Studies on the Reaction of Benzyl Nitrate with Base in Varions Solvents

Canadian Journal of Chemistry ◽

10.1139/v71-644 ◽

1971 ◽

Vol 49 (23) ◽

pp. 3856-3865 ◽

Cited By ~ 1

Author(s):

Carol A. Pollock ◽

P. J. Smith

Keyword(s):

Transition State ◽

Isotope Effect ◽

Kinetic Isotope Effect ◽

Nitrogen Isotope ◽

Minor Role ◽

Solvent Mixtures ◽

Elimination Reaction ◽

Kinetic Isotope ◽

Role Of Solvent

The role of solvent and base on the nature of the transition state for the concerted one-step carbonyl elimination reaction of benzyl nitrate has been examined using rate and kinetic isotope effect techniques. The primary hydrogen–deuterium isotope effect was found to increase with increasing strength of the abstracting base, kH/kD = 5.94 and 6.41 at 30° for reaction with EtO−/EtOH and t-BuO−/t-BuOH, respectively. The nitrogen isotope effect decreased with increasing strength of the abstracting base, 2.07, 1.82, and 1.54% for reaction with OH−/40 vol % EtOH–H2O, EtO−/EtOH, and t-BuO−/t-BuOH, respectively. The conclusion is reached that an increase in the strength of the abstracting base leads to a more reactant-like transition state with decreased rupture of both the C—H and O—N bonds. The role of solvent on the nature of the transition state was examined by determining rates and nitrogen isotope effects for reaction in various ethanol–water and ethanol–dimethyl sulfoxide mixtures. The nitrogen effect was found to remain essentially constant in solvent mixtures ranging from 65 vol % EtOH–H2O on the one hand to 80 vol% EtOH–DMSO on the other hand where the rate constants differed by a factor of 100 fold. It is concluded that solvent plays only a very minor role in determining transition state structure for the concerted elimination reaction of a neutral substrate with base.

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