γ-Deuterium Isotope Effects on Solvolysis of 7-Halonorbornyl Brosylates-6-d

1973 ◽  
Vol 51 (20) ◽  
pp. 3473-3476 ◽  
Author(s):  
Nick H. Werstiuk ◽  
George Timmins ◽  
Frank P. Cappelli
Keyword(s):  
Isotope Effect ◽  
Isotope Effects ◽  
Neighboring Group ◽  
Deuterium Isotope Effects

The γ-deuterium isotope effects for the solvolysis of anti- and syn-7-chloro-, anti- and.syn-7-bromo-exo-2-norbornyl brosylates-6-endo-d and.syn-7-chloro-exo-2-norbornyl brosylate-5,6-exo,exo-d2 in 80:20 EtOH–H2O, 0.04 M NaOAc at 65° are 1.11 ± 0.01, 1.11 ± 0.01, 1.13 ± 0.01, 1.05 ± 0.01, and 1.11 ± 0.01, respectively. The results indicate that the γ-isotope effect observed in the solvolysis of exo-norbornyl brosylate likely is not derived via neighboring group (non-vertical) participation of the C1—C6 bond.

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.

The photodissociation of ammonia in the absorption system. Part I. Deuterium isotope effects in the photodissociation

1977 ◽  
Vol 55 (8) ◽  
pp. 1380-1386 ◽  
Author(s):  
S. Koda ◽  
R. A. Back
Keyword(s):  
Hydrogen Atom ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Quantum Yields ◽  
Absorption System ◽  
System Part ◽  
Deuterium Isotope Effects

The photolyses of mixtures of NH3, NH2D, NHD2, and ND3 have been studied at wave lengths of 2144, 2139, 2062, and 1850 Å in the presence of C3H8 as a hydrogen atom scavenger. Quantum yields of dissociation have the same values for all four species, presumably unity. Analysis of the H2 and HD produced permitted evaluation of intramolecular deuterium isotope effects in the photodissociation of NH2D and ND2H. At the two shortest wavelengths dissociation of H was favored by a factor of 2 or 3, while at 2144 and 2139 Å the isotope effect was much larger. Implications for the mechanism of the predissociation of the Ã-state of ammonia are discussed briefly. The system does not appear to be useful for the photochemical separation of deuterium.

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.

Deuterium Isotope Effects in the Reduction of Cyclohexanones. The Concepts of Steric Approach Control and Product Development Control

1972 ◽  
Vol 50 (3) ◽  
pp. 388-394 ◽  
Author(s):  
Donald C. Wigfield ◽  
David J. Phelps
Keyword(s):  
Product Development ◽  
Transition State ◽  
Isotope Effect ◽  
Steric Hindrance ◽  
Isotope Effects ◽  
Development Control ◽  
Control Product ◽  
Deuterium Isotope Effects ◽  
Early Transition

Definitions for the terms stericapproachcontrol and productdevelopmentcontrol in relation to the degree of bonding in the transition state are put forward. Kinetic deuterium isotope effects in the reduction of a graded series of ketones by NaBH4 and NaBD4 have been measured. These effects are inverse, and show no systematic dependence on the degree of steric hindrance of the ketone. This evidence appears to invalidate the steric approach control – product development control explanation of the axial to equatorial product ratios (1). The primary isotope effect is very small, which is consistent with an early transition state in these reductions, as demanded by other explanations of product ratios, but since several other factors causing small isotope effects may be applicable, the evidence does not constitute proof of an early transition state.The main conclusions of this work have already been published in preliminary form (2).

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.

Secondary deuterium isotope effects on both rate and product determining steps in the thermolysis of 4-methylene-1-pyrazoline

1981 ◽  
Vol 59 (16) ◽  
pp. 2556-2567 ◽  
Author(s):  
Moon Ho Chang ◽  
Robert J. Crawford
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Bond Rupture ◽  
Cleavage Process ◽  
Kinetic Isotope ◽  
Product Distributions ◽  
Deuterium Isotope Effects ◽  
Allylic Radical

The secondary deuterium kinetic isotope effect in the thermolysis of 4-methylene-1-pyrazoline and four of its deuterated isomers has been studied. The value of δΔG≠/n is 142 cal mol−1 if it is a single C—N cleavage process or 71 cal mol−1 if it is a concerted rupture of two C—N bonds. The product distributions can only be rationalized in terms of a mechanism involving a rate determining C—N bond rupture to form a diazenyl diradical intermediate which then can close to methylenecyclopropanes by three possible modes. This requires a secondary isotope effect in the product determining step of 1.33 ± 0.05, for the rotation of CH2 (CD2) out of the plane of the allylic radical in the intermediate.

DEUTERIUM ISOTOPE EFFECTS IN ABSTRACTION OF HYDROGEN ATOMS FROM PHENOLS

1962 ◽  
Vol 40 (4) ◽  
pp. 701-704 ◽  
Author(s):  
R. A. Bird ◽  
G. A. Harpell ◽  
K. E. Russell
Keyword(s):  
Isotope Effect ◽  
Rate Constants ◽  
Isotope Effects ◽  
Hydrogen Abstraction ◽  
Degree Of Polymerization ◽  
Hydrogen Atoms ◽  
Transfer Constant ◽  
Deuterium Isotope Effects

The effect of six deuterated phenols on the rate and degree of polymerization of styrene has been studied. The rate and degree of polymerization are decreased by deuterated phenols to a much less extent than by the corresponding phenols. Approximate transfer constants are estimated, and it is found that the transfer constant for hydrogen abstraction from the deuterated phenol is less than 0.2 of the transfer constant for the normal phenol. The rates of reaction of 2,2-diphenyl-1-picrylhydrazyl with three deuterated phenols have been determined. The rate constants for deuterated 2,6-di-t-butylphenol and 4-bromophenol are less than 0.15 of those for the corresponding phenols, but the isotope effect appears to be small with 4-nitrophenol.

Deuterium isotope effects on the 119Sn shielding constants and spin–spin coupling constants in stannane and the stannonium cation

1987 ◽  
Vol 65 (7) ◽  
pp. 1469-1473 ◽  
Author(s):  
Kevin L. Leighton ◽  
Roderick E. Wasylishen
Keyword(s):  
Isotope Effect ◽  
Isotope Effects ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Chemical Shielding ◽  
Equilibrium Bond Length ◽  
Shielding Constants ◽  
Spin Coupling Constants ◽  
Deuterium Isotope Effects ◽  
Spin Spin Coupling

Deuterium induced isotope effects on the 119Sn chemical shielding constants have been measured for stannane and the stannonium cation; they are found to be approximately −0.403 ppm/D and −0.05 ppm/D respectively. The 119Sn shifts in the series SnDnH4−n (n ≤ 4) deviate from additivity as predicted by Jameson and Osten. The primary and secondary isotope effects on Sn–H spin–spin coupling for stannane were obtained and are −2.8 Hz and −1.7 Hz respectively. The primary isotope effect for Sn–H spin–spin coupling for the stannonium cation was found to be −11.6 ± 7 Hz; an accurate value for the secondary isotope effect on the spin–spin coupling could not be obtained. The derivative of the 119Sn shielding constant and J (Sn,H) with respect to extensions in the equilibrium bond length have been calculated for stannane.

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.

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