Energy switching approach to potential surfaces. III. Three-valued function for the water molecule

1998 ◽  
Vol 108 (18) ◽  
pp. 7623-7630 ◽  
Author(s):  
A. J. C. Varandas ◽  
A. I. Voronin ◽  
P. J. S. B. Caridade
Keyword(s):  
Water Molecule ◽  
Potential Surfaces

Gas-Phase Clustering of NO+ with H2S and H2O

2007 ◽  
Vol 72 (8) ◽  
pp. 1122-1138 ◽  
Author(s):  
Milan Uhlár ◽  
Ivan Černušák
Keyword(s):  
Hydrogen Bonds ◽  
Water Molecule ◽  
Gas Phase ◽  
Saddle Points ◽  
Solvent Molecule ◽  
Local Minima ◽  
Additional Water ◽  
Three Body ◽  
Rain Formation ◽  
Stable Structures

The complex NO+·H2S, which is assumed to be an intermediate in acid rain formation, exhibits thermodynamic stability of ∆Hº300 = -76 kJ mol-1, or ∆Gº300 = -47 kJ mol-1. Its further transformation via H-transfer is associated with rather high barriers. One of the conceivable routes to lower the energy of the transition state is the action of additional solvent molecule(s) that can mediate proton transfer. We have studied several NO+·H2S structures with one or two additional water molecule(s) and have found stable structures (local minima), intermediates and saddle points for the three-body NO+·H2S·H2O and four-body NO+·H2S·(H2O)2 clusters. The hydrogen bonds network in the four-body cluster plays a crucial role in its conversion to thionitrous acid.

DFT study on the hydrolysis of metsulfuron-methyl: A sulfonylurea herbicide

2018 ◽  
Vol 17 (08) ◽  
pp. 1850050 ◽  
Author(s):  
Qiuhan Luo ◽  
Gang Li ◽  
Junping Xiao ◽  
Chunhui Yin ◽  
Yahui He ◽  
...  
Keyword(s):  
Free Energy ◽  
Water Molecule ◽  
Carbonyl Group ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Metsulfuron Methyl ◽  
Catalytic Role ◽  
Hydrolysis Of

Sulfonylureas are an important group of herbicides widely used for a range of weeds and grasses control particularly in cereals. However, some of them tend to persist for years in environments. Hydrolysis is the primary pathway for their degradation. To understand the hydrolysis behavior of sulfonylurea herbicides, the hydrolysis mechanism of metsulfuron-methyl, a typical sulfonylurea, was investigated using density functional theory (DFT) at the B3LYP/6-31[Formula: see text]G(d,p) level. The hydrolysis of metsulfuron-methyl resembles nucleophilic substitution by a water molecule attacking the carbonyl group from aryl side (pathway a) or from heterocycle side (pathway b). In the direct hydrolysis, the carbonyl group is directly attacked by one water molecule to form benzene sulfonamide or heterocyclic amine; the free energy barrier is about 52–58[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. In the autocatalytic hydrolysis, with the second water molecule acting as a catalyst, the free energy barrier, which is about 43–45[Formula: see text]kcal[Formula: see text]mol[Formula: see text], is remarkably reduced by about 11[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is obvious that water molecules play a significant catalytic role during the hydrolysis of sulfonylureas.

Local pseudosymmetry of the water molecule in BaBr2 · 2H2O, a neutron diffraction study

1991 ◽  
Vol 197 (3-4) ◽  
Author(s):  
Th. Kellersohn ◽  
B. Engelen ◽  
H. D. Lutz ◽  
H. Bartl ◽  
B. P. Schweiss ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Water Molecule ◽  
Diffraction Study ◽  
Neutron Diffraction Study

AbstractBarium bromide dihydrate, BaBr

scholarly journals 1H NMR investigation of distal mutant deoxy myoglobins. Interpretation of proximal His contact shifts in terms of a localized distal water molecule.

1994 ◽  
Vol 269 (47) ◽  
pp. 29629-29635
Author(s):  
G N La Mar ◽  
F Dalichow ◽  
X Zhao ◽  
Y Dou ◽  
M Ikeda-Saito ◽  
...  
Keyword(s):  
Water Molecule ◽  
1H Nmr
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