Gas-Phase Basicity of Formaldehyde by the Thermokinetic Method

2000 ◽  
Vol 6 (2) ◽  
pp. 109-112 ◽  
Author(s):  
Guy Bouchoux ◽  
Danielle Leblanc
Keyword(s):  
Fourier Transform ◽  
Proton Transfer ◽  
Equilibrium Constant ◽  
Gas Phase ◽  
Cyclotron Resonance ◽  
Transfer Reactions ◽  
Ion Cyclotron Resonance ◽  
Proton Transfer Reactions ◽  
Ft Icr

A series of proton transfer reactions monitored in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer allows the determination of the gas-phase basicity ( GB) and the proton affinity ( PA) of formaldehyde. The values determined by the thermokinetic method, GB(CH2O) = 681.5 ± 0.7 kJ mol−1 and PA(CH2O) = 711.5 ± 2.1 kJ mol−1 are in excellent agreement with data originating from proton transfer equilibrium constant determinations or from G2 calculations.

Gas phase basicity of dihydropyran and dihydro-1,4-dioxin

1986 ◽  
Vol 64 (7) ◽  
pp. 1295-1297 ◽  
Author(s):  
G. Bouchoux ◽  
I. Hanna ◽  
R. Houriet ◽  
E. Rolli
Keyword(s):  
Double Bond ◽  
Proton Transfer ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Cyclotron Resonance ◽  
Transfer Reactions ◽  
Molecular Orbital Calculations ◽  
Ion Cyclotron Resonance ◽  
Lower Reactivity ◽  
Proton Transfer Reactions

The gas phase basicity (GB) of dihydropyran 1 and dihydro-1,4-dioxin 2 is measured in equilibrium proton transfer reactions conducted in an ion cyclotron resonance spectrometer. GB(1) is found to be greater than GB(2) by 37 kJ mol−1, this difference parallels the lower reactivity of 2 observed in solution under acidic condition. Conclusion as to the favoured protonation of the C—C double bond, giving rise for both 1 and 2 to oxycarbonium cations, is drawn from comparison with analogous compounds and substantiated by molecular orbital calculations (MNDO) on the protonated structures.

Gas-Phase Acidities of Cycloheptatrienes: Effects of Alkyl Groups on the Stability of Carbanions

2002 ◽  
Vol 8 (5) ◽  
pp. 359-366 ◽  
Author(s):  
Masaaki Mishima ◽  
Tomomi Kinoshita ◽  
Yoshitaka Hattori ◽  
Ken'ichi Takeuchi
Keyword(s):  
Mass Spectrometry ◽  
Fourier Transform ◽  
Gas Phase ◽  
Cyclotron Resonance ◽  
Ion Cyclotron Resonance ◽  
Charge Delocalization ◽  
Alkyl Groups ◽  
Respective Parent ◽  
The Stability ◽  
Ft Icr

The gas-phase acidities of 7-alkyl substituted cycloheptatrienes have been determined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry using a proton-transfer equilibrium method, Δ G0acid (kJ mol−1): methyl 1520.0, ethyl 1516.7, n-propyl acid 1513.3, i-propyl 1512.1, n-butyl 1510.4. The effect of alkyl groups on the acidity of cycloheptatriene is linearly correlated with the polarizability parameters ( σα) of substituents, giving a ρα of–55.3 (kJ σ−1α unit). The magnitude of pa is half of that for RCH3 and is significantly larger than that for the fluorene series. These results suggest that the extent of the charge-delocalization in a carbanion plays an important role in determining the susceptibility of the stability of the carbanion to substituent polarizability effects. In addition, comparison of ρ values of acidities of a series of elemental hydrides shows that the numerical value of ρα decreases in the order, C > O ≈ N > S, and that the change of ρα is related to the stability of the respective parent anions (R = H) rather than the atomic electronegativity at the deprotonation center.

Application of experimental (FT-ICR) and theoretical (AM1) methods to the study of proton-transfer reactions for tautomerizing amidines in the gas phase

1996 ◽  
Vol 355 (3-4) ◽  
pp. 412-414 ◽  
Author(s):  
R. W. Taft ◽  
E. D. Raczynska ◽  
P. -C. Maria ◽  
I. Leito ◽  
W. Lewandowski ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Transfer Reactions ◽  
Proton Transfer Reactions ◽  
Ft Icr
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