Ab initio study of the structure of the hydrogen maleate anion

1993 ◽  
Vol 71 (3) ◽  
pp. 303-306 ◽  
Author(s):  
Miguel A. Ríos ◽  
Jesús Rodríguez
Keyword(s):  
Hydrogen Bond ◽  
Proton Transfer ◽  
Ab Initio ◽  
Electron Correlation ◽  
Basis Set ◽  
Ab Initio Methods ◽  
Ab Initio Study ◽  
Barrier Heights ◽  
Minimum Potential ◽  
Complete Optimization

The hydrogen maleate ion was studied by ab initio methods with complete optimization at the 3-21G, 6-31G, 6-31G**, and 6-31+G(2d,1p) levels. To study the influence of electron correlation, MP2 calculations have been done for the 6-31G** geometry. All calculations at the HF level predicted an asymmetric hydrogen bond with a double minimum potential governing transfer between the two equivalent structures. Moreover, both asymmetry and proton transfer barrier increase systematically with the power of the basis set used, with calculated barrier heights of 0.12 (3-21G), 1.59 (6-31G), 1.64 (6-31G**), and 2.00 kcal/mol (6-31+G). Only the introduction of the electron correlation at the MP2 level seems to predict a single minimum potential.

An ab initio study of the structure and intramolecular proton transfer in tropolone

1991 ◽  
Vol 69 (2) ◽  
pp. 201-204 ◽  
Author(s):  
Miguel A. Ríos ◽  
Jesús Rodríguez
Keyword(s):  
Proton Transfer ◽  
Ab Initio ◽  
Ground State ◽  
Vibrational State ◽  
Intramolecular Proton Transfer ◽  
Ab Initio Study ◽  
Proton Tunneling ◽  
Full Optimization ◽  
Minimum Potential ◽  
Intramolecular Hydrogen

An ab initio study of tropolone was carried out at the 3-21G level, with full optimization of the geometry, and the intramolecular proton transfer in the ground state was analysed. The two equivalent Cs structures can be converted to each other via a C2v symmetry transition state with a double minimum potential. The splitting of the ground vibrational state generated by proton tunneling was determined by procedures of variable complexity and found to be in the range Δ = 0.1–0.15 cm−1, i.e., clearly smaller than experimental predictions. Key words: tropolone, intramolecular hydrogen bond, proton transfer, ab initio calculations, molecular structure.

An ab initio Study of the Fulminate Anion-Cyanate Anion Rearrangement: Possible Intermediacy of the Oxazirinyl Anion

1997 ◽  
Vol 50 (2) ◽  
pp. 169 ◽  
Author(s):  
Yu-San Cheung ◽  
Wai-Kee Li
Keyword(s):  
Ab Initio ◽  
Basis Set ◽  
Ab Initio Methods ◽  
Ab Initio Study ◽  
High Level

The rearrangement of the fulminate anion (CNO¯) to the cyanate anion (OCN¯) has been studied with high-level ab initio methods. Geometry optimizations have been carried out at HF, MPn (n = 2-4), QCISD, QUISD(T), BD and BD(T) levels using the 6-31+G(d) basis set. The highest level of theory for the calculation of relative energies is QCISD(T)/6-311+G(3df, 2p). Results show that the rearrangement proceeds via an oxazirinyl anion intermediate, which is separated by barriers of 52·8 and 18·4 kJ mol-1 from CNO¯ and OCN¯, respectively.

Ab initio study of the configuration and protonation of thiocarbamic acid

1989 ◽  
Vol 54 (2) ◽  
pp. 297-302
Author(s):  
Milan Remko
Keyword(s):  
Hydrogen Bond ◽  
Ab Initio ◽  
Intramolecular Hydrogen Bond ◽  
Electron Correlation ◽  
Ab Initio Study ◽  
Proton Affinities ◽  
Moller Plesset ◽  
Intramolecular Hydrogen ◽  
Very High ◽  
Atomic Populations

The ab initio SCF method was applied to a conformation study of thiocarbamic acid. The 3-21 G calculations revealed that the trans isomer with the O-H···S intramolecular hydrogen bond is more stable than the cis isomer. The calculated rotational barrier for the rotation about the central C-N bond is very high, 125.5 kJ mol-1; this value, however, decreased to 106.2 kJ mol-1 by electron correlation determined at the 2nd order Moller-Plesset perturbation level. Proton affinities for the protonation of the electronegative atoms in the acid increase in the order of the atoms N, O and S. Changes in the Mulliken gross atomic populations are examined in dependence on the configuration and protonation of the acid.

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