Observing Proton Transfer Reactions Inside the MALDI Plume: Experimental and Theoretical Insight into MALDI Gas-Phase Reactions

2017 ◽  
Vol 28 (8) ◽  
pp. 1676-1686 ◽  
Author(s):  
Mario F. Mirabelli ◽  
Renato Zenobi
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Transfer Reactions ◽  
Gas Phase Reactions ◽  
Proton Transfer Reactions ◽  
Theoretical Insight ◽  
Insight Into

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.

Gas-phase proton-transfer reactions of the hydronium ion at 298 K

1979 ◽  
Vol 57 (12) ◽  
pp. 1518-1523 ◽  
Author(s):  
Gervase I. Mackay ◽  
Scott D. Tanner ◽  
Alan C. Hopkinson ◽  
Diethard K. Bohme
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Rate Constants ◽  
Transfer Reactions ◽  
Flowing Afterglow ◽  
Hydronium Ion ◽  
Proton Transfer Reactions

Rate constants measured with the flowing afterglow technique at 298 ± 2 K are reported for the proton-transfer reactions of H3O+ with CH2O, CH3CHO, (CH3)2CO, HCOOH, CH3COOH, HCOOCH3, CH3OH, C2H5OH, (CH3)2O, and CH2CO. Dissociative proton-transfer was observed only with CH3COOH. The rate constants are compared with the predictions of various theories for ion–molecule collisions. The protonation is discussed in terms of the energetics and mechanisms of various modes of dissociation.

An experimental study of the reactivity and relative basicity of the methoxide anion in the gas phase at room temperature, and their perturbation by methanol solvation

1982 ◽  
Vol 60 (20) ◽  
pp. 2594-2605 ◽  
Author(s):  
Gervase I. Mackay ◽  
Asit B. Rakshit ◽  
Diethard K. Bohme
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Rate Constants ◽  
Solvent Free ◽  
Transfer Reactions ◽  
Free Proton ◽  
Proton Transfer Reactions ◽  
Intrinsic Reactivity ◽  
Relative Acidity ◽  
Methoxide Anion

Flowing afterglow measurements at 296 ± 2 K are reported which explore three aspects of the gas-phase acid–base chemistry of the methoxide anion. Firstly, the intrinsic reactivity of this ion has been determined from measurements of rate constants for solvent-free proton-transfer reactions with molecules more acidic than methanol including CH2=C=CH2, C6H5CH3, C2H5OH, C2H2, CH3CN, CH3COCH3, CH3CHO, CH3NO2, and HCN. Secondly, equilibrium constant measurements have been performed for solvent-free proton-transfer reactions which provide a gas-phase scale of acidities for these molecules relative to the acidity of methanol. Finally, rate constants were measured for the reactions of these acids with methoxide ions solvated with up to three molecules of methanol. The results establish trends in reactivity as a function of step–wise solvation when relative acidity is preserved and when a reversal occurs in the relative acidity upon solvation.

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