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DFT studies of the conversion of four mesylate esters during reaction with ammonia.

Nowacki A, Sikora K, Dmochowska B, Wiśniewski A - J Mol Model (2013)

Bottom Line: Solvent effect corrections were computed using PCM/B3LYP/6-31+G** level.The bifurcation at C2 causes a significant activation barrier increase.The reaction 4 is the slowest one in all environments.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland. anowacki@chem.univ.gda.pl

ABSTRACT
The energetics of the Menshutkin-like reaction between four mesylate derivatives and ammonia have been computed using B3LYP functional with the 6-31+G** basis set. Additionally, MPW1K/6-31+G** level calculations were carried out to estimate activation barrier heights in the gas phase. Solvent effect corrections were computed using PCM/B3LYP/6-31+G** level. The conversion of the reactant complexes into ion pairs is accompanied by a strong energy decrease in the gas phase and in all solvents. The ion pairs are stabilized with two strong hydrogen bonds in the gas phase. The bifurcation at C2 causes a significant activation barrier increase. Also, bifurcation at C5 leads to noticeable barrier height differentiation. Both B3LYP/6-31+G** and MPW1K/6-31+G** activation barriers suggest the reaction 2 (2a + NH3) to be the fastest in the gas phase. The reaction 4 is the slowest one in all environments.

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Geometries of the stationary points and ΔE (kcal mol−1) computed at the B3LYP/6-31+G** level for reactions 1 and 2 in the gas phase. Selected distances in Å, and valence angles in degrees
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Fig5: Geometries of the stationary points and ΔE (kcal mol−1) computed at the B3LYP/6-31+G** level for reactions 1 and 2 in the gas phase. Selected distances in Å, and valence angles in degrees

Mentions: The calculated geometries together with selected bond distances, valence angles and relative energies corresponding to all the stationary points along the reaction pathway are presented in Figs. 5 and 6. The relative energies refer to the sum of the separate reactant energies.Fig. 5


DFT studies of the conversion of four mesylate esters during reaction with ammonia.

Nowacki A, Sikora K, Dmochowska B, Wiśniewski A - J Mol Model (2013)

Geometries of the stationary points and ΔE (kcal mol−1) computed at the B3LYP/6-31+G** level for reactions 1 and 2 in the gas phase. Selected distances in Å, and valence angles in degrees
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3713272&req=5

Fig5: Geometries of the stationary points and ΔE (kcal mol−1) computed at the B3LYP/6-31+G** level for reactions 1 and 2 in the gas phase. Selected distances in Å, and valence angles in degrees
Mentions: The calculated geometries together with selected bond distances, valence angles and relative energies corresponding to all the stationary points along the reaction pathway are presented in Figs. 5 and 6. The relative energies refer to the sum of the separate reactant energies.Fig. 5

Bottom Line: Solvent effect corrections were computed using PCM/B3LYP/6-31+G** level.The bifurcation at C2 causes a significant activation barrier increase.The reaction 4 is the slowest one in all environments.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland. anowacki@chem.univ.gda.pl

ABSTRACT
The energetics of the Menshutkin-like reaction between four mesylate derivatives and ammonia have been computed using B3LYP functional with the 6-31+G** basis set. Additionally, MPW1K/6-31+G** level calculations were carried out to estimate activation barrier heights in the gas phase. Solvent effect corrections were computed using PCM/B3LYP/6-31+G** level. The conversion of the reactant complexes into ion pairs is accompanied by a strong energy decrease in the gas phase and in all solvents. The ion pairs are stabilized with two strong hydrogen bonds in the gas phase. The bifurcation at C2 causes a significant activation barrier increase. Also, bifurcation at C5 leads to noticeable barrier height differentiation. Both B3LYP/6-31+G** and MPW1K/6-31+G** activation barriers suggest the reaction 2 (2a + NH3) to be the fastest in the gas phase. The reaction 4 is the slowest one in all environments.

Show MeSH