Towards a complete account of diastereotopic hydrogen isotope exchange of carbon acids. III. Base-catalyzed exchange of sulfoxides. Evidence for exchange by inversion

1985 ◽  
Vol 63 (8) ◽  
pp. 2100-2109 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Sujit Banerjee
Keyword(s):  
Steady State ◽  
Rate Constants ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Hydrogen Isotope Exchange ◽  
Upper Limit ◽  
Steady State Assumption ◽  
Carbon Acids ◽  
State Assumption ◽  
Complete Account

The rate constants for deuteroxide and hydroxide catalyzed H → D and D → H exchange of benzodihydrothiophene oxide (1a) and several of its deuterated analogs 1b, 1c, and 1d at 30.00 ± 0.05 °C are reported along with the rate constants for D → H exchange of deuterated benzyl methyl sulfoxides 2b and 2c. Application of the steady-state assumption to schemes involving equilibrating pyramidal anions yield equations which are used to fit experimentally determined (kf/ks)H → D and (kf/ks)D → H ratios. The analysis supports our view that exchange of the diastereotopic protons (deuterons) occurs by inversion. The inversion component contributes significantly to exchange of the "slow" proton (deuteron) of a diastereotopic pair and this accounts for the observation that (kf/ks)D → H < (kf/ks)H → D. This study establishes an upper limit of 6 kcal for the barrier to inversion of the carbanions derivable from 1 and 2, if pyramidal anions are formed.

Towards a complete account of the mechanism of hydrogen isotope exchange of diastereotopic protons of carbon acids. II. Acid- and base-catalyzed enolization of bicyclo[2.2.1]heptan-2-ones. Evidence for exchange by inversion

1985 ◽  
Vol 63 (2) ◽  
pp. 534-541 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Sujit Banerjee
Keyword(s):  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Significant Contribution ◽  
Hydrogen Isotope Exchange ◽  
Acid And Base ◽  
Carbon Acids ◽  
Acid Catalyzed ◽  
Rate Ratios ◽  
Carbon Acid ◽  
Complete Account

A study of acid- and base-catalyzed hydrogen isotope exchange of bicyclo[2.2.1]heptan-2-one (1a) and its 3-deuteriated analogs has been carried out. We find that the kexo/kendo ratio (658 ± 66) for deuteroxide-catalyzed H → D exchange of 1a at C-3 is 7.2 ± 1.5 times greater than the kexo/kendo ratio (91 ± 9) for hydroxide-catalyzed D → H exchange of 1b. For acid-catalyzed exchange in CH3COOD(H)–D(H)Cl the rate ratios are 156 ± 20 and 29 ± 2 for H → D and D → H exchange, respectively. Equations which relate the observed selectivity kexo/kendo (kfast/kslow) to the intrinsic selectivity and the primary, secondary, and solvent KIEs are developed. The differences between the rate ratios for H → D and D → H exchange are interpreted on the basis of a significant contribution of an inversion pathway to exchange of the slow proton (deuteron). The significance of our study – it relates to the mechanism of hydrogen isotope exchange of diastereotopic protons (deuterons, tritons) of any carbon acid – is discussed.

Base-catalyzed hydrogen isotope exchange of thiocamphor: α-thioenolization rate constants

1978 ◽  
Vol 56 (19) ◽  
pp. 2605-2606 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Paul Andrews
Keyword(s):  
Exchange Rate ◽  
Rate Constants ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Deuterium Exchange ◽  
Hydrogen Isotope Exchange

The rates of base-catalyzed protium–deuterium exchange (α-thioenolization) of the exo and endo protons of thiocamphor (1), in 2:1 dioxane-D2O at 25.0 ± 0.5 °C, have been determined by monitoring the uptake of deuterium mass spectrometrically. The exo and endo exchange rate constants, 2.20 × 10−2 and 5.60 × 10−4 M−1 s−1, respectively, are 23.2 and 12.3 times larger than the rate constants for exo and endo exchange in camphor (2). Factors which may determine the rate enhancements are discussed.

scholarly journals Are rate and selectivity correlated in iridium-catalysed hydrogen isotope exchange reactions?

2021 ◽  
Author(s):  
Daria S. Timofeeva ◽  
David M Lindsay ◽  
W. J. Kerr ◽  
David James Nelson
Keyword(s):  
Functional Groups ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Reaction Rate ◽  
Exchange Reactions ◽  
Reaction Selectivity ◽  
Hydrogen Isotope Exchange ◽  
The Relationship

Herein we examine the relationship between reaction rate and reaction selectivity in iridium-catalysed hydrogen isotope exchange (HIE) reactions directed by Lewis basic functional groups. We have recently develped a directing...

Hydrogen isotope exchange between D2 and H2O catalyzed by platinum plate

1989 ◽  
Vol 67 (5) ◽  
pp. 857-861 ◽  
Author(s):  
Shin-Ichi Miyamoto ◽  
Tetsuo Sakka ◽  
Matae Iwasaki
Keyword(s):  
Kinetic Model ◽  
Exchange Reaction ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Reaction Rate ◽  
Hydrogen Adsorption ◽  
Platinum Catalyst ◽  
Isotope Exchange Reaction ◽  
Hydrogen Isotope Exchange ◽  
Supported Platinum

The reaction rate of hydrogen isotope exchange between D2 and H2O catalyzed by platinum plate is studied. The exchange reaction is described with the kinetic model which is the modification of that for the exchange reaction catalyzed by alumina-supported platinum catalyst. For the comparison of experimental results with this model relative amount of the number of sites for hydrogen adsorption was estimated from the initial rate of hydrogen isotope exchange between H2 and D2 on the same surface. The results show that the kinetic model is applicable for the plate catalyst if the number of the sites for hydrogen absorption, which is very sensitive to the surface state of the catalyst, was estimated not from the macroscopic surface area but from our scheme. Keywords: hydrogen isotope exchange reaction, platinum plate as catalyst.

Two-film effects on the kinetics of hydrogen isotope exchange between CHCl3 and D2O in two liquid phase system

1993 ◽  
Vol 25 (5) ◽  
pp. 363-374
Author(s):  
Matae Iwasaki ◽  
Tetsuo Sakka ◽  
Shigeyuki Ohashi ◽  
Yoshikazu Miyake ◽  
Hiroshi Matsushita
Keyword(s):  
Liquid Phase ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Phase System ◽  
Hydrogen Isotope Exchange ◽  
Kinetics Of
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