Intrinsic acidities of substituted phenols and benzoic acids determined by gas-phase proton-transfer equilibriums

1977 ◽  
Vol 99 (7) ◽  
pp. 2222-2230 ◽  
Author(s):  
T. B. McMahon ◽  
P. Kebarle
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Benzoic Acids ◽  
Substituted Phenols

Stabilities in the gas phase of the hydrogen bonded complexes, YC6H4OH-X−, of substituted phenols, YC6E4OH, with the halide anions X− (Cl−, Br−, I−)

1990 ◽  
Vol 68 (11) ◽  
pp. 2070-2077 ◽  
Author(s):  
Gary J. C. Paul ◽  
Paul Kebarle
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Proton Transfer ◽  
Gas Phase ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Closed Shell ◽  
Bond Energies ◽  
Substituted Phenols ◽  
Hydrogen Bonded

The equilibria, YPhOH + Br− = YPhOH-Br−, involving 26 differently substituted phenols, were determined with a pulsed high pressure mass spectrometer. The −ΔG0 evaluated from the equilibrium constants represent the hydrogen bond free energies in YPhOH-Br−. These data and data for X− = Cl− and I−, determined previously in this laboratory, are used to examine the substituent effects on the hydrogen bonding. It was found that the hydrogen bond energies in YPhOH-X− increase approximately linearly with the gas phase acidities of the phenols, YPhOH. This is in agreement with earlier observations that showed the bond energies in AH-B−, where AH were oxygen and nitrogen acids and B− closed shell anions, increase with increasing acidity of AH.A detailed analysis of the substituent effects, which is possible for YPhOH-X−, shows that the relationship with the acidity of AH can be divided into two parts. One is the increasing extent of actual proton transfer from AH on formation of the hydrogen bonded complex. Such proton transfer occurs in YPhOH-X− only for the series X− = Cl−. The second effect, which occurs for Cl− and is dominant for Br− and I−, is not directly related to the acidity of the phenols (or AH in general) but depends on a similarity of the substituent effects on the acidity and the stabilization of YPhOH-X− (or AH-B− in general). The dominant contribution to YPhOH-X− stabilization in this case is due to the field effects of the substituents, i.e., π delocalization plays only a small part. Therefore, the correlation with the acidity of YPhOH, where π delocalization is important, is not very close. Keywords: hydrogen bonding, substituent effects, ion–molecule equilibria, stability constants, thermochemistry.

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.

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.

scholarly journals Reactions between neutral molecules and cation-radicals in the gas-phase: Can protonation occur without proton transfer?

2015 ◽  
Vol 390 ◽  
pp. 39-48
Author(s):  
Yury V. Vasil’ev ◽  
Douglas F. Barofsky ◽  
Joseph S. Beckman ◽  
Benjamin J. Bythell
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Cation Radicals
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