γ-RADIATION-INDUCED HYDROGEN EXCHANGE REACTION IN LIQUID CYCLOHEXANE – HYDROGEN CHLORIDE SOLUTIONS

1966 ◽  
Vol 44 (22) ◽  
pp. 2645-2649 ◽  
Author(s):  
J. W. Fletcher ◽  
G. R. Freeman
Keyword(s):  
Exchange Reaction ◽  
Hydrogen Chloride ◽  
Hydrogen Exchange ◽  
Spectroscopic Method ◽  
Exchange Reactions ◽  
Radical Chain ◽  
Chloride System ◽  
Γ Radiation ◽  
Radiation Induced ◽  
A Chain

The overall exchange reactions[Formula: see text]have been initiated by radiolysis and measured by a nuclear magnetic resonance spectroscopic method. The reactions occur by a chain mechanism, with a chain length of ~ 104 in a 1 M solution of hydrogen chloride in cyclohexane. The mechanism is complex.The exchange reaction can also be initiated by the photolysis of chlorine or of hydrogen chloride.A chain exchange reaction does not occur between c-C6H12 and DI, D2S, or ND3. These results are consistent with the suggestion that the exchange reaction in the cyclohexane – hydrogen chloride system occurs by a free radical chain mechanism.This type of exchange reaction can cause difficulties in isotopic tracer studies.

scholarly journals A proton-magnetic-resonance study of hydrogen-exchange reactions of yeast tryptophan synthase

1991 ◽  
Vol 273 (3) ◽  
pp. 605-610
Author(s):  
C J Bailey ◽  
J P G Malthouse
Keyword(s):  
Exchange Reaction ◽  
Hydrogen Exchange ◽  
Ph Dependence ◽  
Proton Exchange ◽  
Free Enzyme ◽  
Tryptophan Synthase ◽  
Exchange Reactions ◽  
Exponential Decay Rate ◽  
Base Form ◽  
Catalytic Constant

1H n.m.r. was used to observe tryptophan formation from indole and L-serine, proton exchange at C-2 of L-tryptophan, and proton exchange at C-2 of L-serine, catalysed by yeast tryptophan synthase in the presence of 2H2O. Tryptophan synthesis took place with compulsory replacement of C-2 hydrogen by solvent hydrogen. The exponential decay rate (kobs) of the serine exchange reaction was insensitive to serine concentration in the range 2-20mM and was used to calculate kcat./Km values. However, kobs. was very sensitive to pH* values in the range 6.5-8.5 and the data require that the free enzyme is active in the base form resulting from two inseparable ionizations of pKa 7.3, and inactive after a third ionization controlled by a pKa of 7.5. Initial rates measured by u.v. absorbance and colorimetric procedures were used to calculate kinetic parameters of the tryptophan synthesis reaction. From pH 6.5 to 7, kcat./Km values for L-serine in the tryptophan synthesis and hydrogen exchange reactions were indistinguishable and increased rapidly under the control of two acid-base groups of pKa 6.7 and 7.2. Above pH 7, this equivalence breaks down because the exchange reaction alone is responsive to the third pKa value of the free enzyme. The pH dependence of the catalytic constant for tryptophan synthesis was qualitatively similar to that of the kobs. for serine exchange. A mechanism to explain the results is contrasted with recent proposals for the Escherichia coli system.

scholarly journals The exchange reactions between deuterium and hydrogen halides. II. Hydrogen bromide

1939 ◽  
Vol 173 (955) ◽  
pp. 531-542 ◽  
Keyword(s):  
Exchange Reaction ◽  
Hydrogen Chloride ◽  
Hydrogen Bromide ◽  
Bimolecular Reaction ◽  
Exchange Reactions ◽  
Hydrogen Halides ◽  
Type D ◽  
Analogous System ◽  
Theoretical Considerations

This investigation into the exchange reaction of deuterium and hydrogen bromide was carried out in order to substantiate some results obtained in Part I on the reactions of deuterium and hydrogen chloride. It was desired to find out how the change to the analogous system affects the bimolecular reaction observed in the hydrogen chloride case and also to obtain some more information concerning reactions of the type D + HA→DA + H, which from the theoretical considerations given in Part I have unusual characteristics.

Kinetics of hydrogen isotope exchange reactions - XXIX. Radiation-induced tritiation of 1, 4-dioxan in aqueous solutions

1975 ◽  
Vol 346 (1647) ◽  
pp. 443-467 ◽  
Keyword(s):  
Hydrogen Exchange ◽  
High Reactivity ◽  
Exchange Reactions ◽  
High Concentration ◽  
Γ Irradiation ◽  
Solvated Electrons ◽  
Radiation Chemical ◽  
Molecular Product ◽  
Chemical Studies ◽  
Radiation Induced

Under the influence of tritium β-radiation, 1, 4-dioxan undergoes hydrogen exchange with the solvent water. The inhibition of the reaction by known electron scavengers (Ag + , Cu 2+ , Ni 2+ , Co 2+ , Zn 2+ , H + 3 O and also by species with high reactivity towards hydroxyl radicals but negligible reactivity towards solvated electrons (N - 3 , Br - , SCN - ) has been examined in detail. γ-Irradiation similarly induces hydrogen exchange. The action of scavengers is interpreted as requiring the involvement of two separately scavengeable primary radiolysis products in the sequence of reactions leading to exchange. Evidence is presented that the reactions of these species occur in spur regions, and the scheme RH + OH˙→ R˙ + H 2 O e - aq → R - HTO → RT is considered to explain the main features of the mechanism. The presence of electron scavengers, even at high concentration, does not totally inhibit the exchange, and a secondary exchange route, involving a lower valency state of inhibitor cations, is considered responsible for the ‘unscavengeable’ portion of the reaction, by providing an alternative exchange route, e. g. R˙ + Ni + → R - + Ni 2+ HTO → RT Analogies are drawn between the exchange reaction and other radiation-induced reactions that are thought to involve spur processes (such as the formation of H 2 O 2 as a molecular product in the radiolysis of water). Some implications of the present results for the interpretation of radiation-chemical studies in water-alcohol mixtures are indicated.

Radiation-induced Rearrangement of Ethylene Glycol in Aqueous Solution

1971 ◽  
Vol 49 (14) ◽  
pp. 2382-2389 ◽  
Author(s):  
C. E. Burchill ◽  
K. M. Perron
Keyword(s):  
Hydrogen Peroxide ◽  
Ethylene Glycol ◽  
Aqueous Solutions ◽  
Transfer Reaction ◽  
Major Product ◽  
Hydrogen Atom Transfer ◽  
Γ Irradiation ◽  
Radical Chain ◽  
Radiation Induced ◽  
A Chain

Under γ-irradiation, aqueous solutions of ethylene glycol containing hydrogen peroxide form acetaldehyde as a major product via a free-radical chain rearrangement. The yield of acetaldehyde is essentially unchanged when hydrogen peroxide is replaced by N2O or HClO4. A mechanism is proposed in which the glycol radical, ĊOHCH2OH, rearranges to the acetaldehyde precursor, ĊH2CHO, followed by the hydrogen atom transfer reaction;[Formula: see text]thus propagating a chain reaction.2The rearrangement is also induced by the photo-dissociation of H2O2 in aqueous solutions of ethylene glycol.

Transalkylierung und protonenkatalysierte C-C-Spaltung bei n-Butyl-und n-Pentylbenzol in der Gasphase / Transalkylation and Proton Catalyzed C-C-Cleavage of Gaseous n-Butyl and w-Pentyl Benzenes

1979 ◽  
Vol 34 (3) ◽  
pp. 495-501 ◽  
Author(s):  
C. Wesdemiotis ◽  
H. Schwarz ◽  
C. C. Van de Sande ◽  
F. Van Gaever
Keyword(s):  
Hydrogen Exchange ◽  
Closed Shell ◽  
Open Shell ◽  
Molecular Ions ◽  
Exchange Reactions ◽  
Intramolecular Exchange ◽  
Carbon Carbon Bond ◽  
Exchange Processes ◽  
Reaction Channels ◽  
Alkyl Benzenes

Abstract The investigation of several 13carbon and deuterium labelled n-butyl and n-pentyl benzenes demonstrate that chemical ionization (reagent gas: methane) induces specific carbon-carbon bond cleavages of the alkyl group. The extent of competing reaction channels as for instance direct alkene elimination versus dealkylation/reprotonation is analyzed. Partial hydrogen exchange processes between reagent ions and substrate molecules are restricted to the phenyl ring. Intramolecular exchange reactions between the side chain and the aromatic ring which are typical for the open shell molecular ions of alkyl benzenes are not observed for analogous closed shell cations.

Preparation of Functionalized Diorganomagnesium Reagents in Toluene via Bromine or Iodine/Magnesium-Exchange Reactions

Synthesis ◽  
2021 ◽  
Author(s):  
Alexandre Desaintjean ◽  
Fanny Danton ◽  
Paul Knochel
Keyword(s):  
Exchange Reaction ◽  
Nitro Group ◽  
General Formula ◽  
Functional Groups ◽  
Exchange Reactions ◽  
Acyl Chlorides ◽  
Aryl Iodides ◽  
Highly Sensitive ◽  
Wide Range ◽  
Magnesium Exchange

A wide range of polyfunctionalized di(hetero)aryl- and dialkenyl-magnesium reagents were prepared in toluene within 10 to 120 min between −78 °C and 25 °C via an I/Mg- or Br/Mg-exchange reaction using reagents of the general formula R2Mg (R = sBu, Mes). Highly sensitive functional groups, such as a triazene or a nitro group, were tolerated in these exchange reactions, enabling the synthesis of various functionalized (hetero)arenes and alkenes derivatives after quenching with several electrophiles including allyl bromides, acyl chlorides, aldehydes, ketones, and aryl iodides.

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