THE HYDROGEN ISOTOPE EFFECT IN THE PYROLYSIS OF ETHYL-1,1,2,2-d4 CHLORIDE

1962 ◽  
Vol 40 (8) ◽  
pp. 1526-1532 ◽  
Author(s):  
Arthur T. Blades ◽  
P. W. Gilderson ◽  
M. G. H. Wallbridge
Keyword(s):  
Isotope Effect ◽  
Hydrogen Isotope ◽  
Pressure Effect ◽  
Relative Rate ◽  
Isotope Effects ◽  
Deuterium Atom ◽  
Qualitative Explanation ◽  
Relative Rate Constant ◽  
Hydrogen Isotope Effect ◽  
Constant Expression

The hydrogen isotope effect in the pyrolysis of ethyl-1,1,2,2-d4 chloride has been investigated in the temperature range 758–989 °C, yielding the relative rate constant expression[Formula: see text]where kH and kD are the rate constants for the production of C2D4 (and HCl) and of C2D3H (and DCl) per β-deuterium atom respectively.The isotope effect is pressure dependent, its value increasing with decreasing pressure. The pressure effect in ethyl chloride has also been studied, and a qualitative explanation is given for the pressure dependence of intermolecular and intramolecular isotope effects.The data are compared with the isotope effects in ethyl-d4 bromide and ethyl-d4 acetate, and the conclusion is reached that the evidence supports a four-centered transition-state complex in the case of the halides.

THE HYDROGEN ISOTOPE EFFECTS IN THE PYROLYSIS OF ETHYL-1,1,2,2-d4 BROMIDE AND OF ETHYL-d5 BROMIDE

1962 ◽  
Vol 40 (8) ◽  
pp. 1533-1539 ◽  
Author(s):  
Arthur T. Blades ◽  
P. W. Gilderson ◽  
M. G. H. Wallbridge
Keyword(s):  
Isotope Effect ◽  
Rate Constant ◽  
Hydrogen Isotope ◽  
Relative Rate ◽  
Isotope Effects ◽  
Side Reaction ◽  
Relative Rate Constant ◽  
Temperature Range ◽  
Rate Controlling Step ◽  
Constant Expression

The relative rate constant expression has been obtained for the decomposition of ethyl-1,1,2,2-d4 bromide under inhibiting conditions in the temperature range 697.6 to 999.1 °K,[Formula: see text]The pressure dependence of the isotope effect has been investigated both with and without inhibitor, and in each case it has been shown that the isotope effect increases with decreasing pressure.The relative rate constant expression for the ethyl-h5, ethyl-d5 bromide comparison was also obtained in the temperature range 730.9 to 964.8 °K,[Formula: see text]The isotope effect is again pressure dependent, falling to lower values as the pressure is decreased.The data are used to demonstrate that the inhibited decomposition of ethyl bromide is primarily a molecular process, and that the rate-controlling step involves a carbon–hydrogen bond break.A side reaction that produces small amounts of ethane has been observed.

THE SECONDARY HYDROGEN ISOTOPE EFFECTS IN THE PYROLYSIS OF ETHYL-d5 ACETATE AND ETHYL ACETATE-d3

1960 ◽  
Vol 38 (9) ◽  
pp. 1407-1411 ◽  
Author(s):  
Arthur T. Blades ◽  
P. W. Gilderson
Keyword(s):  
Ethyl Acetate ◽  
Rate Constant ◽  
Hydrogen Isotope ◽  
Experimental Error ◽  
Relative Rate ◽  
Isotope Effects ◽  
Relative Rate Constant ◽  
Temperature Ranges ◽  
Relative Rate Constants ◽  
Constant Expression

Rate constant expressions have been obtained for ethyl acetate and ethyl-d5 acetate in the temperature ranges 500–603 °C and 501–614 °C.[Formula: see text]By measuring the relative rate of production of C2H4 and C2D4 from identical mixtures of the two esters at the temperatures 387 and 490 °C, it has been possible to determine the temperature coefficient of the relative rate constant more accurately. This, coupled with the relative rate constants at 500 °C derived from the above equations, gives the relative rate constant expression.[Formula: see text]These data are compared with the intramolecular isotope effect in the decomposition of ethyl-1,1,2,2-d4 acetate, and the differences attributed to secondary isotope effects.The rate of decomposition of ethyl acetate-d3 was found to be identical within experimental error with that of the normal acetate.

The hydrogen isotope effect in the bromination of 2-carbethoxy cyclo pentanone

1956 ◽  
Vol 235 (1203) ◽  
pp. 453-468 ◽  
Keyword(s):  
Isotope Effect ◽  
Hydrogen Isotope ◽  
Deuterium Oxide ◽  
Isotope Effects ◽  
Activation Energies ◽  
Tunnel Effect ◽  
Fluoride Ion ◽  
Energy Barriers ◽  
Hydrogen Isotope Effect ◽  
Kinetics Of

Measurements are reported on the kinetics of the base-catalyzed bromination of 2-car-bethoxycyclopentanone, with either hydrogen or deuterium in the active position. The solvent throughout was deuterium oxide, the catalysts employed were the solvent, monochloroacetate ion and fluoride ion, and measurements were made at 5° intervals over the range 10 to 70°C. The observed activation energies are all greater for the deutero- than for the proto-ester, but the differences are greater than would be expected on current theories of isotope effects. The observed collision factors are in every case greater for deuterium than for hydrogen, especially for catalysis by fluoride ion, where the ratio of these factors is A D / A H = 24 ± 4. These observations can only be accounted for by invoking the tunnel effect, i. e. by supposing that the motion of the proton is markedly non-classical in nature. It is shown that this hypothesis leads to reasonable dimensions for the energy barriers involved, and some if its general consequences are discussed.

scholarly journals KINETIC HYDROGEN ISOTOPE EFFECTS IN AROMATIC BROMODEPROTONATION

1966 ◽  
Vol 44 (3) ◽  
pp. 379-386 ◽  
Author(s):  
B. T. Baliga ◽  
A. N. Bourns
Keyword(s):  
Isotope Effect ◽  
Hydrogen Isotope ◽  
Salt Effect ◽  
Isotope Effects ◽  
Effect Study ◽  
Ion Concentration ◽  
Bromide Ion ◽  
Halogenation Reaction ◽  
Hydrogen Isotope Effect ◽  
Step Mechanism

The bromodeprotonation of sodium p-methoxybenzenesulfonate is an ordinary halogenation reaction in which a hydrogen ortho to the methoxy group is replaced by bromine. The kinetic data for this reaction do not distinguish between a one- and a two-step mechanism with Br2 as the brominating species. The two-step mechanism was confirmed by the observation of a variation in the kinetic hydrogen isotope effect, kH/kD, with changing bromide ion concentration. The observed isotope effects are 1.01, 1.07, 1.18, and 1.31 at bromide ion concentrations 0, 0.5, 1, and 2 M, respectively.The isotope effect study strongly establishes that in this reaction the small depression in rate produced by bromide ion, beyond that due to Br3− formation, arises mainly from a salt effect, and only a small amount of this depression is caused by return of the intermediate to reactants.

Kinetic hydrogen isotope effects in the ionization of some ketonic substances

1965 ◽  
Vol 286 (1406) ◽  
pp. 285-299 ◽  
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Hydrogen Isotope ◽  
Organic Molecule ◽  
Isotope Effects ◽  
Methyl Malonate ◽  
Ethyl Malonate ◽  
Hydrogen Isotope Effect ◽  
Catalytic Power ◽  
Basic Strength

The kinetic hydrogen isotope effect has been measured for the water-catalysed bromination of acetylacetone, monobromoacetylacetone, ethyl acetoacetate, ethyl α-bromoacetoacetate, ethyl α-methylacetoacetate, ethyl malonate, ethyl monobromomalonate, and methyl methyl - malonate and for the bromination of ethyl a-methylacetoacetate catalysed by six basic anions. All these reactions are of zero order with respect to bromine, so that the process studied is the rate of transfer of a proton or deuteron from the organic molecule to the catalyst. For ethyl a-methylacetoacetate there is a correlation between the basic strength of the catalyst, the rate of proton transfer, and the magnitude of the isotope effect. Various possible explanations are considered for the variation in isotope effect, and it is concluded that current interpretations in terms of a three-centre model of the transition state are inadequate. The isotope effect also varies considerably with the nature of the organic molecule, but is not in general related to its reactivity. There is, however, a correlation between the magnitude of the isotope effect and the exponent β of the Brönsted relation between basic strength and catalytic power, suggesting that both quantities depend on the position of the proton in the transition state.

Interpretation of the hydrogen isotope effect on the density limit in JET-ILW L-mode plasmas using EDGE2D-EIRENE

2021 ◽  
Vol 96 (12) ◽  
pp. 124028
Author(s):  
V Solokha ◽  
M Groth ◽  
G Corrigan ◽  
S Wiesen
Keyword(s):  
Isotope Effect ◽  
Hydrogen Isotope ◽  
Density Limit ◽  
Hydrogen Isotope Effect

Reaction selectivity, hydrogen isotope effect and steric hindrance in the aromatic halogenation of polyalkylbenzenes

1960 ◽  
Vol 1 (44) ◽  
pp. 30-34 ◽  
Author(s):  
Enrico Baciocchi ◽  
Gabriello Illuminati ◽  
Giancarlo Sleiter
Keyword(s):  
Isotope Effect ◽  
Steric Hindrance ◽  
Hydrogen Isotope ◽  
Reaction Selectivity ◽  
Hydrogen Isotope Effect

Hydrogen Isotope Fractionation in Aqueous Alkaline Earth Chloride Solutions

2007 ◽  
Vol 62 (12) ◽  
pp. 721-728 ◽  
Author(s):  
Masahisa Kakiuchi
Keyword(s):  
Isotope Effect ◽  
Hydrogen Isotope ◽  
Alkaline Earth ◽  
Platinum Catalyst ◽  
Pure Water ◽  
Pressure Ratio ◽  
Hydrogen Gas ◽  
Chloride Solutions ◽  
Aqueous Chloride ◽  
Hydrogen Isotope Effect

The D/H ratio of hydrogen gas in equilibrium with aqueous alkaline earth (Mg, Ca, Sr or Ba) chloride solutions measured at 25◦C using a hydrophobic platinum catalyst, was found to be higher than the D/H ratio equilibrated with the applied pure water. The hydrogen isotope effect between such solutions and pure water changes with the molality of the solutions. The order of the D/H ratios in alkaline earth chlorides is found to be BaCl2 > SrCl2 ≥ CaCl2 ≥ MgCl2. The hydrogen isotope effect in the aqueous chloride solutions of Mg, Ca, Sr or Ba ions is significantly larger than that in the aqueous chloride solutions of Li, Na, K or Cs ions. For MgCl2 and CaCl2 solutions, the hydrogen isotope effect is opposite to the oxygen isotope effect. The results are compared with the free energy change of transfer from H2O to D2O, and are discussed for the vapour pressure ratio of H2O and D2O of CaCl2 solutions.

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