scholarly journals Deuterium Isotope Effects in the Oxidation of 2,3-Dimethyl-2-butene via the Bromohydroperoxide, by Singlet Oxygen and by Triphenyl Phosphite Ozonide

1972 ◽  
Vol 50 (24) ◽  
pp. 4034-4049 ◽  
Author(s):  
Karl R. Kopecky ◽  
Johan H. van de Sande
Keyword(s):  
Singlet Oxygen ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Bond Breaking ◽  
Triphenyl Phosphite ◽  
Deuterium Isotope Effect ◽  
Major Isomer ◽  
Deuterium Isotope Effects ◽  
Oxygen Oxidation ◽  
Cis And Trans

The partially deuterated alkenes (CH3)2C = C(CD3)2 (1b) and CH3CD3C = CCH3CD3 (1c) were prepared and converted to the corresponding allylic hydroperoxides by the routes shown in the title. Two bromohydroperoxides were formed from 1b in a 1.6:1 ratio with the major isomer having the OOH group on the carbon bearing the CH3's. On treatment with base at 0° this mixture formed two allylic hydroperoxides in a 2.2:1 ratio with the major isomer having the OOH group on the carbon bearing the CD3's, showing migration of the OOH group. This isomer predominated in a 1.4:1 ratio when 1b was oxidized with singlet oxygen at 15 or −52° and in a 1.6:1 ratio when 1b was oxidized with triphenyl phosphite ozonide at −70°. Under the same conditions C—H bond breaking also predominated in the oxidation of 1c, by 2.1:1 via the bromohydroperoxide, by 1.4:1 with singlet oxygen, and by 1.3:1 with triphenyl phosphite ozonide. Migration of the OOH group in the reaction of the bromohydroperoxide of 1b does not occur by way of a 1,2-dioxetane. A perepoxide may be the intermediate. Neither perepoxides nor 1,2-dioxetanes are involved in the singlet oxygen oxidation of 1b and c. At −70° the triphenyl phosphite ozonide oxidations do not proceed by way of these intermediates, either, or by way of singlet oxygen. The intermolecular deuterium isotope effect in the singlet oxygen oxidation of both cis- and trans-2,3-diphenyl-2-butene was found to be 1.1.

The Preparation and Acetolyses of 5-Deuteriated exo-2-Norbornyl-p-bromobenzenesulfonates

1972 ◽  
Vol 50 (5) ◽  
pp. 618-626 ◽  
Author(s):  
N. H. Werstiuk ◽  
R. R. MacDonald ◽  
R. W. Ouwehand ◽  
W. L. Chan ◽  
F. P. Cappelli ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Deuterium Isotope Effect ◽  
Hydrogen Deuterium ◽  
Deuterium Isotope Effects

The deuterionorborneols 2a, b, c, and e have been prepared and converted to the brosylates 1a, b, c, and e. The deuterium isotope effects determined spectrophotometrically for solvolysis in HOAc–KOAc are 1.00 ± 0.01, 1.01 ± 0.01, 0.99 ± 0.01, and 1.11 ± 0.01, respectively. These data establish that: (a) a steric deuterium isotope effect does not operate at C-5 and therefore probably not at C-6; (b) hyperconjugative stabilization of the norbornonium ion to the C-5 hydrogens is confirmed to be not important, and (c) provides the first experimental evidence that the hydrogen (deuterium) shift – internal return pathway contribution to the γ-deuterium isotope effects observed for 1d and e is minor.

Kinetic β-deuterium isotope effects for solvolysis of 1-methyl cyclopentyl chloride in an ethanol+ water mixture

1983 ◽  
Vol 61 (1) ◽  
pp. 116-117
Author(s):  
Ross Elmore Robertson ◽  
Edward Wong ◽  
John Marshall William Scott ◽  
Michael Jesse Blandamer ◽  
Rehmat Khan ◽  
...  
Keyword(s):  
Isotope Effect ◽  
Kinetic Data ◽  
Isotope Effects ◽  
Water Mixture ◽  
Deuterium Isotope Effect ◽  
Deuterium Isotope Effects

Kinetic data are reported for the solvolysis of 1-methyl cyclopentyl chloride in a 50% by volume ethanol+ water mixture. These data are combined with kinetic data for solvolysis of three deuterated analogues; 1-methyl-d3 cyclopentyl chloride, 1-methyl-2,2,5,5-d4 cyclopentyl chloride, and 1-methyl-d3-2,2,5,5-d4 cyclopentyl chloride, being the d3d4, and d7, derivatives respectively. The kinetic data are used to calculate the kinetic deuterium isotope effect, kH/kD. For these systems, the d7-isotope effect is close to the product of the d3 and d4 effects.

A Primary Hydrogen-Deuterium Isotope Effect Study on the Carbonyl Elimination Reaction of 9-Fluorenyl Nitrate with Various Bases

1975 ◽  
Vol 53 (2) ◽  
pp. 263-268 ◽  
Author(s):  
Peter James Smith ◽  
Lorraine Marion Noble
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Effect Study ◽  
Elimination Reaction ◽  
Deuterium Isotope Effect ◽  
Nitrogen Bases ◽  
Transition State Geometry ◽  
Hydrogen Deuterium ◽  
Deuterium Isotope Effects

The carbonyl elimination reaction of 9-fluorenyl nitrate with various nitrogen bases in anhydrous ethanol at 0 °C was examined. In all cases fluorenone was formed in 100% yield indicating that there was not any substitution. A reasonable Brønsted plot was obtained for reaction promoted by structurally similar bases with β = 0.84 which suggests a product-like transition state. As well, deviations from the Brønsted plot are discussed. Primary hydrogen-deuterium isotope effects were measured for reaction promoted by 11 different amine bases. A reasonable correlation was obtained for structurally similar bases when a plot of kH/kDvs. pKa was made. The conclusion is reached that when kH/kD reaches a maximum, ∼9.2 at 0 °C, it remains unchanged and hence is a poor measure of transition state geometry. As well, very poor correlations are found when the abstracting base is tertiary which leads to the conclusion that a comparison of kH/kD values is not warranted for structurally different bases.

Some Deuterium Isotope Effects. III.1aAn Inverse γ-Deuterium Isotope Effect

1960 ◽  
Vol 82 (24) ◽  
pp. 6315-6318 ◽  
Author(s):  
K. T. Leffek ◽  
J. A. Llewellyn ◽  
R. E. Robertson
Keyword(s):  
Isotope Effect ◽  
Isotope Effects ◽  
Deuterium Isotope Effect ◽  
Deuterium Isotope Effects

Kinetic deuterium isotope effects and kinetic solvent isotope effects for the solvolyses in water and in water + acetonitrile mixtures related to a series of substituted benzyl nitrates

1980 ◽  
Vol 58 (20) ◽  
pp. 2142-2145 ◽  
Author(s):  
Mohammed Ahsan ◽  
Ross Elmore Robertson ◽  
Michael Jesse Blandamer ◽  
John Marshall William Scott
Keyword(s):  
Aqueous Solution ◽  
Benzene Ring ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Bond Breaking ◽  
Relative Importance ◽  
Stage Process ◽  
Deuterium Isotope Effects ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

In aqueous solution, the α-deuterium isotope effects in the solvolyses of benzyl nitrates derivatives depend on the nature of the substituent in the benzene ring. In addition, the isotope effect for some derivatives depends on mole fraction of added acetonitrile while for others the isotope effect is insensitive to solvent composition. However, the kinetic solvent isotope effects for para-methyl and meta-trifluoromethyl derivatives remain unchanged when acetonitrile is added. These observations are accounted for in terms of a model which describes the solvolytic reaction as a two-stage process and contrasts the relative importance of bond-making and bond-breaking.

Berechnung kinetischer Isotopeneffekte für die Reaktion von Methyljodid mit Cyanid-Ion

1966 ◽  
Vol 21 (9) ◽  
pp. 1377-1384
Author(s):  
A. V. Willi
Keyword(s):  
Transition State ◽  
Secular Equation ◽  
Isotope Effects ◽  
Force Constants ◽  
Bond Breaking ◽  
Bending Force ◽  
A Value ◽  
Order Of Magnitude ◽  
Deuterium Isotope Effects ◽  
The Difference

Kinetic carbon-13 and deuterium isotope effects are calculated for the SN2 reaction of CH3I with CN-. The normal vibrational frequencies of CH3I, the transition state I · · · CH3 · · · CN, and the corresponding isotope substituted reactants and transition states are evaluated from the force constants by solving the secular equation on an IBM 7094 computer.Values for 7 force constants of the planar CH3 moiety in the transition state (with an sp2 C atom) are obtained by comparison with suitable stable molecules. The stretching force constants related to the bonds being broken or newly formed (fCC, fCC and the interaction between these two stretches, /12) are chosen in such a way that either a zero or imaginary value for νʟ≠ will result. Agreement between calculated and experimental methyl-C13 isotope effects (k12/ k13) can be obtained only in sample calculations with sufficiently large values of f12 which lead to imaginary νʟ≠ values. Furthermore, the difference between fCI and fCC must be small (in the order of 1 mdyn/Å). The bending force constants, fHCI and fHCC, exert relatively little influence on k12/k13. They are important for the D isotope effect, however. As soon as experimental data on kH/kD are available it will be possible to derive a value for fHCC in the transition state if fHCI is kept constant at 0.205 mdynA, and if fCI, fCC and f12 are held in a reasonable order of magnitude. There is no agreement between experimental and calculated cyanide-C13 isotope effects. Possible explanations are discussed. — Since fCI and fCC cannot differ much it must be concluded that the transition state is relatively “symmetric”, with approximately equal amounts of bond making and bond breaking.

?-Secondary deuterium isotope effect and solvent isotope effects in catalysis by subtilisin BPN?

1990 ◽  
Vol 3 (4) ◽  
pp. 260-265 ◽  
Author(s):  
Ildiko M. Kovach ◽  
Son Do ◽  
Richard L. Schowen
Keyword(s):  
Isotope Effect ◽  
Isotope Effects ◽  
Deuterium Isotope Effect ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

2,4-Diazapentadienes. II. A Carbanion Cyclization

1972 ◽  
Vol 50 (5) ◽  
pp. 678-689 ◽  
Author(s):  
D. H. Hunter ◽  
S. K. Sim
Keyword(s):  
Isotope Effect ◽  
Solvent Effects ◽  
Isotope Effects ◽  
Substituent Effects ◽  
Deuterium Exchange ◽  
Hydrogen Deuterium Exchange ◽  
Deuterium Isotope Effect ◽  
Potassium Methoxide ◽  
Proton Shift ◽  
Hydrogen Deuterium

The mechanism of the cyclization and 1,3-proton shift of 1,3,5-triaryl-2,4-diaza-1,3-pentadienes (1) catalyzed by phenyllithium and by potassium methoxide–methanol has been studied. On the basis of substituent effects, hydrogen–deuterium exchange, isotope effects, and solvent effects, it was deduced that both the cyclization and prototropy involve a common W-shaped carbanion which rapidly cyclizes. A kinetic deuterium isotope effect of 2 was calculated for protonation of this intermediate carbanion in methanol.

SOME DEUTERIUM KINETIC ISOTOPE EFFECTS: IV. β-DEUTERIUM EFFECTS IN WATER SOLVOLYSIS OF ETHYL, ISOPROPYL, AND tert-BUTYL COMPOUNDS

1960 ◽  
Vol 38 (11) ◽  
pp. 2171-2177 ◽  
Author(s):  
K. T. Leffek ◽  
J. A. Llewellyn ◽  
R. E. Robertson
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Alkyl Halides ◽  
Tert Butyl ◽  
Kinetic Isotope ◽  
Deuterium Isotope Effects ◽  
Intramolecular Forces

The secondary β-deuterium isotope effects have been measured in the water solvolytic reaction of alkyl halides and sulphonates for primary, secondary, and tertiary species. In every case the kinetic isotope effect was greater than unity (kH/kD > 1). This isotope effect may be associated with varying degrees of hyperconjugation or altered non-bonding intramolecular forces. The experiments make it difficult to decide which effect is most important.

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