Is There a Transition-State Imbalance for Proton Transfers in the Gas Phase? Ab Initio Study of the Carbon-to-Carbon Proton Transfer from Acetaldehyde to Its Enolate Ion

1994 ◽  
Vol 116 (12) ◽  
pp. 5405-5413 ◽  
Author(s):  
Claude F. Bernasconi ◽  
Philip J. Wenzel
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Ab Initio ◽  
Gas Phase ◽  
Ab Initio Study ◽  
Proton Transfers

Identity-reaction proton transfers from oxygen acids yielding localized vs. delocalized conjugate bases. An ab initio study

1999 ◽  
Vol 77 (5-6) ◽  
pp. 810-816 ◽  
Author(s):  
James E Van Verth ◽  
William H Saunders, Jr.
Keyword(s):  
Proton Transfer ◽  
Ab Initio ◽  
Gas Phase ◽  
Heavy Atom ◽  
Proton Donor ◽  
Proton Transfers ◽  
Straight Line ◽  
Large Positive Deviation ◽  
Experimental Values ◽  
Conjugate Bases

Identity-reaction proton transfers from a series of oxygen acids to the corresponding conjugate bases have been studied by ab initio methods at the MP2/6-31+G*//MP2/6-31+G* level. The acids are H3O+, CH3OH2+, CH2 = OH+, HC(O)OH2+, CH2 = CHOH2+, H2O, CH3OH, HOOH, HOCH2OH, FOH, FCH2OH, HC(O)OH, and CH2 = CHOH. Gas-phase acidities were calculated at the G2(MP2) level in order to have benchmark values for all acidities regardless of whether experimental values were available. Barriers to proton transfer relative to the separated reactants, ΔHTS, show a straight-line relation to acidity for all but two of the neutral acids and for all but one of the cationic acids. Two neutral acids, HOOH and FOH, show negative deviations that can be attributed to polarizability of the atoms attached to the proton donor oxygens. The cationic acid HC(O)OH2+ shows a large positive deviation, which probably arises from substantial heavy-atom reorganization from reactant to TS. Charges provide evidence of a lag in delocalization in the reaction of CH2 = CHOH2+, though it does not show an elevated ΔHTS.Key words: ab initio, oxygen acids, proton transfer, acidity.

Ab Initio Study of Gas-Phase Proton Transfer in Ammonia−Hydrogen Halides and the Influence of Water Molecules

1999 ◽  
Vol 103 (38) ◽  
pp. 7719-7724 ◽  
Author(s):  
James A. Snyder ◽  
Robert A. Cazar ◽  
Alan J. Jamka ◽  
Fu-Ming Tao
Keyword(s):  
Proton Transfer ◽  
Ab Initio ◽  
Gas Phase ◽  
Water Molecules ◽  
Ab Initio Study ◽  
Hydrogen Halides ◽  
Influence Of Water
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