Transition State Imbalances in Gas Phase Proton Transfers.Ab InitioStudy of the Carbon-to-Carbon Proton Transfer from the Protonated Acetaldehyde Cation to Acetaldehyde Enol

1996 ◽  
Vol 118 (43) ◽  
pp. 10494-10504 ◽  
Author(s):  
Claude F. Bernasconi ◽  
Philip J. Wenzel
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Gas Phase ◽  
Protonated Acetaldehyde

The Mechanism(S) of the Addition of Alcohols to Protonated Acetone in the Gas-Phase

1986 ◽  
Vol 39 (6) ◽  
pp. 839 ◽  
Author(s):  
JC Sheldon ◽  
GJ Currie ◽  
JH Bowie
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Gas Phase ◽  
Cyclotron Resonance ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
The Other ◽  
Ion Cyclotron Resonance ◽  
Gas Phase Reactions ◽  
Flowing Afterglow

The gas phase reactions of the systems Me2C=+OH/ROH (R = Me and Pri ) have been investigated by using a combination of experimental [ion cyclotron resonance ( i.c.r .) and flowing afterglow ( f.a .)] and ab initio (4-31G, GAUSSIAN 82) methods. A stabilized adduct, thought to correspond to Me2C=+OH...O(H)R, is observed when R = Pri but not for Me. Decomposing forms of adducts eliminate water; 18O labelling shows the major (overall) reaction to be Me2C=+OH+R18OH → Me2C=+(18O)R+H2OAb initio calculations indicate ( i ) that the product ion in this reaction is produced by two channels, both proceeding through Me2(HO)C-+O(H)R; one directly, the other indirectly through Me2C=+OH...O(H)R, and (ii) that the transition state for the key proton transfer reaction Me2(HO)C-+O(H)Me → Me2( MeO )C-+OH2 is of higher energy than reactants. The latter result suggests that precursor ion Me2C=+O needs to be vibrationally hot for the elimination of water to occur: a comparison of i.c.r . and f.a . experiments confirms this to be the case.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

Electron-Transfer-Induced Side-Chain Cleavage in Tryptophan Facilitated through Potassium-Induced Transition-State Stabilization in the Gas Phase

2021 ◽  
Author(s):  
Filipe Ferreira da Silva ◽  
Tiago Cunha ◽  
Andre Rebelo ◽  
Adrià Gil ◽  
Maria José Calhorda ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Transition State ◽  
Gas Phase ◽  
Side Chain ◽  
Side Chain Cleavage ◽  
Transition State Stabilization ◽  
Chain Cleavage

Ab Initio Study of the Carbon-to-Carbon Identity Proton Transfer from Ketene to Its Anion in the Gas Phase

2001 ◽  
Vol 123 (10) ◽  
pp. 2430-2431 ◽  
Author(s):  
Claude F. Bernasconi ◽  
Philip J. Wenzel
Keyword(s):  
Proton Transfer ◽  
Ab Initio ◽  
Gas Phase ◽  
Ab Initio Study

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.

ChemInform Abstract: TRANSITION-STATE PLIABILITY IN NITROGEN-TO-NITROGEN PROTON TRANSFER

1983 ◽  
Vol 14 (33) ◽  
Author(s):  
F. M. MENGER ◽  
J. GROSSMAN ◽  
D. C. LIOTTA
Keyword(s):  
Proton Transfer ◽  
Transition State
Sign in / Sign up

Export Citation Format

Share Document