Amide hydrolysis. IV. Proton transfer and heavy-atom reorganization in amide hydrolysis. Valence-isomeric transition states

1971 ◽  
Vol 93 (8) ◽  
pp. 2014-2024 ◽  
Author(s):  
Richard L. Schowen ◽  
Larry D. Kershner
Keyword(s):  
Proton Transfer ◽  
Heavy Atom ◽  
Transition States ◽  
Isomeric Transition ◽  
Amide Hydrolysis

Understanding difficulties of irregular number-membered ring transition states for intramolecular proton transfer in excited state

Tetrahedron ◽  
2017 ◽  
Vol 73 (4) ◽  
pp. 403-410 ◽  
Author(s):  
Xiaozhuan Qin ◽  
Ge Ding ◽  
Zhenqiang Wang ◽  
Yulong Gong ◽  
Fang Gao ◽  
...  
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Transition States ◽  
Intramolecular Proton Transfer ◽  
Membered Ring

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.

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.

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