Gas-Phase Reactions of Carbocations with Amines. Isotope Effects in Proton Transfer

1994 ◽  
Vol 98 (23) ◽  
pp. 5931-5934 ◽  
Author(s):  
Giuseppi Laguzzi ◽  
Thomas H. Osterheld ◽  
John I. Brauman
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Isotope Effects ◽  
Gas Phase Reactions

An experimental study of the reactivity of the hydroxide anion in the gas phase at room temperature, and its perturbation by hydration

1981 ◽  
Vol 59 (11) ◽  
pp. 1615-1621 ◽  
Author(s):  
Scott D. Tanner ◽  
Gervase I. Mackay ◽  
Diethard K. Bohme
Keyword(s):  
Experimental Study ◽  
Proton Transfer ◽  
Gas Phase ◽  
Rate Constants ◽  
Room Temperature ◽  
Gas Phase Reactions ◽  
Flowing Afterglow ◽  
Hydroxide Anion

Flowing afterglow measurements are reported which provide rate constants and product identifications at 298 ± 2 K for the gas-phase reactions of OH− with CH3OH, C2H5OH, CH3OCH3, CH2O, CH3CHO, CH3COCH3, CH2CO, HCOOH, HCOOCH3, CH2=C=CH2, CH3—C≡CH, and C6H5CH3. The main channels observed were proton transfer and solvation of the OH−. Hydration with one molecule of H2O was observed either to reduce the rate slightly and lead to products which are the hydrated analogues of the "nude" reaction, or to stop the reaction completely, k ≤ 10−12 cm3 molecule−1 s−1. The reaction of OH−•H2O with CH3—C≡CH showed an uncertain intermediate behaviour.

Collision-induced elimination of alkenes from deprotonated unsaturated ethers in the gas phase. Reactions involving specific .beta.-proton transfer

1990 ◽  
Vol 112 (7) ◽  
pp. 2537-2541 ◽  
Author(s):  
Russell J. Waugh ◽  
Roger N. Hayes ◽  
Peter C. H. Eichinger ◽  
K. M. Downard ◽  
John H. Bowie
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Gas Phase Reactions

Hydration of acetone in the gas phase and in water solvent

2010 ◽  
Vol 88 (1) ◽  
pp. 56-64 ◽  
Author(s):  
Kiyull Yang ◽  
Yih-Huang Hsieh ◽  
Chan-Kyung Kim ◽  
Hui Zhang ◽  
Saul Wolfe
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Isotope Effects ◽  
Bond Formation ◽  
Transition States ◽  
Water Solvent ◽  
Cooperative Process

In water solvent, the hydration of acetone proceeds by a cyclic (cooperative) process in which concurrent C–O bond formation and proton transfer to oxygen take place through a solvent and (or) catalyst bridge. Reactivity is determined primarily by the concentration of a reactant complex and not the barrier from this complex. This situation is reversed in the gas phase; although the concentrations of reactive complexes are much higher than in solution, the barriers are also higher and dominant in determining reactivity. Calculations of isotope effects suggest that multiple hydron transfers are synchronous in the gas phase to avoid zwitterionic transition states. In solution, such transition states are stabilized by solvation and hydron transfers can be asynchronous.

Activation of methane by gaseous platinum(II) ions PtX+ (X = H, Cl, Br, CHO)

2005 ◽  
Vol 83 (11) ◽  
pp. 1936-1940 ◽  
Author(s):  
Detlef Schröder ◽  
Helmut Schwarz
Keyword(s):  
Mass Spectrometry ◽  
Key Words ◽  
Electrospray Ionization ◽  
Gas Phase ◽  
Bond Activation ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Methane Activation ◽  
Gas Phase Reactions ◽  
Kinetic Isotope

The gas-phase reactions of methane with the platinum(II) ions PtX+ with X = H, Cl, Br, and CHO are studied by mass spectrometry. The PtX+ ions are generated by electrospray ionization of methanolic solutions of hexachloroplatinic acid and hexabromoplatinic acid, respectively. Small to moderate intramolecular kinetic isotope effects determined for the C—H(D) bond activation of CH2D2 suggest that the activation of methane by gaseous PtX+ cations is subject to thermochemical control by the product channels. In addition, the PtCl2+ cation is also able to activate methane, whereas PtCl3+ is unreactive under the conditions chosen. Key words: gas-phase reactions, mass spectrometry, methane activation, platinum bromide, platinum chloride.

Oxidative dealkylation of aromatic amines by "bare" FeO+ in the gas phase

1999 ◽  
Vol 77 (5-6) ◽  
pp. 774-780 ◽  
Author(s):  
Mark Brönstrup ◽  
Detlef Schröder ◽  
Helmut Schwarz
Keyword(s):  
Gas Phase ◽  
Bond Activation ◽  
Isotope Effects ◽  
Gas Phase Reactions ◽  
Electron Transfer Mechanism ◽  
Gas Phase Chemistry ◽  
Kinetic Isotope ◽  
Phase Chemistry ◽  
Cytochrome P 450 ◽  
Mass Spectrometric Techniques

The gas-phase oxidations of aniline, N-methylaniline, and N,N-dimethylaniline by FeO+ cation are examined by using mass spectrometric techniques. Although bare FeO+ is capable of hydroxylating aromatic C—H bonds, the fate of the oxidation of arylamines is determined by docking of the FeO+ unit at nitrogen. The major reactions of the metastable aniline/FeO+ complex are losses of molecular hydrogen, ammonia, and water, all involving at least one N-H proton. N-alkylation results in a complete shift of the course of the reaction. The unimolecular processes observed can be regarded as initial steps of an oxidative dealkylation of the amines mediated by FeO+. More detailed mechanistic insight is obtained by examining the C—H(D) bond activation of N-methyl-N-([D3]-methyl)aniline by bare and ligated FeO+ species. The gas-phase reactions of FeO+ with methylanilines show some similarities to the enzymatic dealkylation of amines by cytochrome P-450. The kinetic isotope effects observed experimentally suggest an electron transfer mechanism for the gas-phase reaction.Key words: mass spectrometry, gas-phase chemistry, iron, dealkylation, N,N-dimethylaniline.

Marcus theory and the existence or non-existence of transition states in gas phase deprotonation of carbon acids

1984 ◽  
Vol 62 (8) ◽  
pp. 1465-1469 ◽  
Author(s):  
Saul Wolfe
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Transition States ◽  
Marcus Theory ◽  
Energy Change ◽  
Transfer Reactions ◽  
Gas Phase Reactions ◽  
Proton Transfer Reactions ◽  
Carbon Acids ◽  
Computational Level

At the 3-21G (3-21G*) computational level, the intrinsic barriers associated with proton transfer between XCH2− and CH3X have been found to be essentially constant (ca. 10 kcal/mol) for X = H, F, SH, Cl. According to the Marcus rate-equilibrium treatment of proton transfer reactions, this result means that transition states should not exist for gas phase reactions [Formula: see text], when the energy change exceeds 20 kcal/mol. This prediction has been confirmed for two cases (X = H, F) in which the energy change is less than 20 kcal/mol, and two cases (X = SH, Cl) in which the energy change is greater than 20 kcal/mol.

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