Symmetry and tunneling in proton transfer reactions. Proton exchange between methyloxonium ion and methyl alcohol, methyl alcohol and methoxide ion, hydronium ion and water, and water and hydroxyl ion

Busch, J. H.; Vega, J. R. De La

doi:10.1021/ja00450a001

Cited by 41 publications

(11 citation statements)

References 5 publications

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“…It may be remarked here that the potentials we have considered have physical relevance. For example, the parabolic potential of the form given in eqn (5) has been used in a number of references cited at the beginning of Section 1.…”

Section: Discussionmentioning

confidence: 99%

Tunnelling in asymmetric double-well potentials: varying initial states

Cordes

Das

2001

Superlattices and Microstructures

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Section: Discussionmentioning

confidence: 99%

Tunnelling in asymmetric double-well potentials: varying initial states

Cordes

Das

2001

Superlattices and Microstructures

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“…2 *(A2,,) = -5 5 (Cg(n,3,j)+.,(n,x) cos ( +,(n,x), and k = 1,5 (or f l ) combined with +,(n,x) will produce the two-dimensional ir-reducible representation Eg while the two other matrices combine k = f 2 with the + , ( a x ) and k = f l with.the +.,(n,x) to give the two-dimensional irreducible representation E,: (16) "(E,) = -1 5 This matrix with the use of eq 12 gives the AI, and A2" symmetry species.…”

Section: + Cu(n3j)+(nx) Cos ( 6 J + 3)o) (13)mentioning

confidence: 99%

Effect of the methyl group rotation on the rate of intramolecular proton exchange in .alpha.-methyl-.beta.-hydroxyacrolein

Busch¹,

Fluder²,

Vega³

1980

J. Am. Chem. Soc.

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Ab initio S C F calculations were used to determine the potential-energy profile for the intramolecular proton exchange in a-methyl-P-hydroxyacrolein for various orientations of the methyl group. The proton transfer was found to occur only when the methyl group orientation causes the transfer profile to be symmetric. Thus rotation and transfer were seen to be strongly coupled, in agreement with experimental evidence. An analytical two-dimensional potential representing the coupled motion was fitted to the S C F energies obtained. From the eigenstates of the potential the splitting of the two nondegenerate A levels and that of the lowest degenerate E levels were calculated and found in reasonable agreement with those estimated from experimental data.

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“…Known experimental splittings for hydrogen atom tunneling span a range of more than eight orders of magnitudes, with most of them being (far) smaller than 1 cm

(

0.01 kJ mol

) [ 15 ]. For this reason, localization is the typical, but not the strict, outcome from symmetry breaking by chemical [ 3 , 16 , 17 , 18 , 19 ] or isotopic [ 4 , 5 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ] substitution, internal rotation of molecular groups [ 6 , 16 , 20 , 24 , 29 ], or from environmental influences such as solvation [ 16 , 30 ], matrix embedding [ 3 , 31 , 32 ] or crystallization [ 33 ]. However, delocalization can still be observed upon excitation if either the barrier [ 3 , 5 , 21 , 25 , 26 , 29 ] or the energetic asymmetry [ 22 , 34 ] are sufficiently lowered.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of Alpha-Fenchol

et al. 2021

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Rotational microwave jet spectroscopy studies of the monoterpenol α-fenchol have so far failed to identify its second most stable torsional conformer, despite computational predictions that it is only very slightly higher in energy than the global minimum. Vibrational FTIR and Raman jet spectroscopy investigations reveal unusually complex OH and OD stretching spectra compared to other alcohols. Via modeling of the torsional states, observed spectral splittings are explained by delocalization of the hydroxy hydrogen atom through quantum tunneling between the two non-equivalent but accidentally near-degenerate conformers separated by a low and narrow barrier. The energy differences between the torsional states are determined to be only 16(1) and 7(1) cm−1hc for the protiated and deuterated alcohol, respectively, which further shrink to 9(1) and 3(1) cm−1hc upon OH or OD stretch excitation. Comparisons are made with the more strongly asymmetric monoterpenols borneol and isopinocampheol as well as with the symmetric, rapidly tunneling propargyl alcohol. In addition, the third—in contrast localized—torsional conformer and the most stable dimer are assigned for α-fenchol, as well as the two most stable dimers for propargyl alcohol.

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Symmetry and tunneling in proton transfer reactions. Proton exchange between methyloxonium ion and methyl alcohol, methyl alcohol and methoxide ion, hydronium ion and water, and water and hydroxyl ion

Cited by 41 publications

References 5 publications

Tunnelling in asymmetric double-well potentials: varying initial states

Tunnelling in asymmetric double-well potentials: varying initial states

Effect of the methyl group rotation on the rate of intramolecular proton exchange in .alpha.-methyl-.beta.-hydroxyacrolein

Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of Alpha-Fenchol

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