Why Does Pivalaldehyde (Trimethylacetaldehyde) Unexpectedly Seem More Basic Than 1-Adamantanecarbaldehyde in the Gas Phase? FT-ICR and High-Level Ab Initio Studies

2005 ◽  
Vol 11 (6) ◽  
pp. 1826-1832 ◽  
Author(s):  
Esther Quintanilla ◽  
Juan Z. Dávalos ◽  
José-Luis M. Abboud ◽  
Manuel Alcamí ◽  
M. Pilar Cabildo ◽  
...  
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
High Level ◽  
Ft Icr

The cubyl cation rearrangements

2016 ◽  
Vol 52 (16) ◽  
pp. 3403-3405 ◽  
Author(s):  
Said Jalife ◽  
Sukanta Mondal ◽  
Jose Luis Cabellos ◽  
Gerardo Martinez-Guajardo ◽  
Maria A. Fernandez-Herrera ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Molecular Dynamics Simulations ◽  
Gas Phase ◽  
Dynamics Simulations ◽  
High Level

Born–Oppenheimer molecular dynamics simulations and high-level ab initio computations predict that the cage-opening rearrangement of the cubyl cation to the 7H+-pentalenyl cation is feasible in the gas phase.

Structure and Reactivity of Protonated α,α,α-Trifluorotoluene in the Gas Phase. A Combined FT-ICR, Radiolytic, and ab Initio MO Study

1996 ◽  
Vol 100 (51) ◽  
pp. 19859-19863 ◽  
Author(s):  
Massimiliano Aschi ◽  
Barbara Chiavarino ◽  
Maria Elisa Crestoni ◽  
Simonetta Fornarini
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Ab Initio Mo ◽  
Ft Icr

GAS-PHASE REACTIONS OF V+ AND VO+ WITH METHANOL

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2693-2698 ◽  
Author(s):  
YALI CAO ◽  
XIANG ZHAO ◽  
ZICHAO TANG ◽  
BIN XIN ◽  
SHAOXIANG XIONG
Keyword(s):  
Reaction Time ◽  
Dft Calculations ◽  
Ab Initio ◽  
Gas Phase ◽  
Reaction Mechanisms ◽  
Ab Initio Calculation ◽  
Gas Phase Reactions ◽  
Geometrical Structures ◽  
Reaction Processes ◽  
Ft Icr

The reactions of V + and VO + with methanol have been investigated experimentally by FT-ICR mass spectrometer and theoretically by ab initio calculation. Both V + and VO + exhibit impressive reactivity with methanol. The products distribution of different reaction time indicate that in whole reaction processes methanol is adsorbed one by one, and no more than four methanol molecules can be solved in the first shell of central ion V +. The reaction mechanisms have been proposed, and the possible geometrical structures of products are also analyzed by DFT calculations.

Halide–Nitrogen Gas-Phase Clusters: Anion Photoelectron Spectroscopy and High Level ab Initio Calculations

2015 ◽  
Vol 119 (37) ◽  
pp. 9722-9728 ◽  
Author(s):  
Kim M. L. Lapere ◽  
Marcus Kettner ◽  
Peter D. Watson ◽  
Allan J. McKinley ◽  
Duncan A. Wild
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Gas Phase ◽  
Photoelectron Spectroscopy ◽  
Nitrogen Gas ◽  
Gas Phase Clusters ◽  
Anion Photoelectron Spectroscopy ◽  
High Level

scholarly journals Thermochemistry of Guanine Tautomers Re-Examined by Means of High-Level CCSD(T) Composite Ab Initio Methods

2019 ◽  
Vol 72 (8) ◽  
pp. 607 ◽  
Author(s):  
Amir Karton
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Basis Set ◽  
Energy Window ◽  
Small Energy ◽  
Composite Methods ◽  
Wide Range ◽  
Complete Basis Set ◽  
Enol Tautomer ◽  
High Level

We obtained accurate gas-phase tautomerization energies for a set of 14 guanine tautomers by means of high-level thermochemical procedures approximating the CCSD(T) energy at the complete basis set (CBS) limit. For the five low-lying tautomers, we use the computationally demanding W1-F12 composite method for obtaining the tautomerization energies. The relative W1-F12 tautomerization enthalpies at 298K are: 0.00 (1), 2.37 (2), 2.63 (3), 4.03 (3′), and 14.31 (4) kJmol−1. Thus, as many as four tautomers are found within a small energy window of less than 1.0kcalmol−1 (1kcalmol−1=4.184kJmol−1). We use these highly accurate W1-F12 tautomerization energies to evaluate the performance of a wide range of lower-level composite ab initio procedures. The Gn composite procedures (G4, G4(MP2), G4(MP2)-6X, G3, G3B3, G3(MP2), and G3(MP2)B3) predict that the enol tautomer (3) is more stable than the keto tautomer (2) by amounts ranging from 0.36 (G4) to 1.28 (G3(MP2)) kJmol−1. We also find that an approximated CCSD(T)/CBS energy calculated as HF/jul-cc-pV{D,T}Z+CCSD/jul-cc-pVTZ+(T)/jul-cc-pVDZ results in a root-mean-square deviation (RMSD) of merely 0.11kJmol−1 relative to the W1-F12 reference values. We use this approximated CCSD(T)/CBS method to obtain the tautomerization energies of 14 guanine tautomers. The relative tautomerization enthalpies at 298K are: 0.00 (1), 2.20 (2), 2.51 (3), 4.06 (3′), 14.30 (4), 25.65 (5), 43.78 (4′), 53.50 (6′), 61.58 (6), 77.37 (7), 82.52 (8′), 86.02 (9), 100.70 (10), and 121.01 (8) kJmol−1. Using these tautomerization enthalpies, we evaluate the performance of standard and composite methods for the entire set of 14 guanine tautomers. The best-performing procedures emerge as (RMSDs are given in parentheses): G4(MP2)-6X (0.51), CCSD(T)+ΔMP2/CBS (0.52), and G4(MP2) (0.64kJmol−1). The worst performers are CCSD(T)/AVDZ (1.05), CBS-QB3 (1.24), and CBS-APNO (1.38kJmol−1).

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