Charge distributions and chemical effects. XXX. Relationships between nuclear magnetic resonance shifts and atomic charges

1982 ◽  
Vol 104 (20) ◽  
pp. 5287-5292 ◽  
Author(s):  
Sandor Fliszar ◽  
Guy Cardinal ◽  
Marie Therese Beraldin
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Atomic Charges ◽  
Charge Distributions ◽  
Chemical Effects ◽  
Nuclear Magnetic

Charge distributions and chemical effects. XXVI. Relationships between nuclear magnetic resonance shifts and atomic charges for 17O nuclei in ethers and carbonyl compounds

1982 ◽  
Vol 60 (2) ◽  
pp. 106-110 ◽  
Author(s):  
Marie-Thérèse Béraldin ◽  
Edouard Vauthier ◽  
Sándor Fliszár
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Oxygen Atom ◽  
Carbonyl Compounds ◽  
Electronic Charge ◽  
Atomic Charges ◽  
Chemical Effects ◽  
Opposite Trend ◽  
Nuclear Magnetic ◽  
Oxygen Atoms

The 17O nuclear magnetic resonance shifts of dialkylethers are linearly related to the electron populations on the oxygen atoms, in a range covering L ~ 130 ppm, showing that any increase of electronic charge at the oxygen atom is accompanied by a downfield nmr shift. The opposite trend is observed for the oxygen atoms of ketones and aldehydes.

The Basis for the Hard-Water Antagonism of Glyphosate Activity

Weed Science ◽  
1995 ◽  
Vol 43 (4) ◽  
pp. 541-548 ◽  
Author(s):  
Kurt D. Thelen ◽  
Evelyn P. Jackson ◽  
Donald Penner
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Ammonium Sulfate ◽  
Hard Water ◽  
Calcium Antagonism ◽  
Chemical Effects ◽  
Spray Solution ◽  
Type Complex ◽  
Over Time ◽  
Nuclear Magnetic

Hard-water cations, such as Ca+2and Mg+2, present in the spray solution can greatly reduce the efficacy of glyphosate. These cations potentially compete with the isopropylamine in the formulation for association with the glyphosate anion.14C-Glyphosate absorption by sunflower was reduced in the presence of Ca+2. The addition of ammonium sulfate overcame the observed decrease in14C-glyphosate absorption. Nuclear Magnetic Resonance (NMR) was used to study the chemical effects of calcium and calcium plus ammonium sulfate (AMS) on the glyphosate molecule. Data indicate an association of calcium with both the carboxyl and phosphonate groups on the glyphosate molecule. Initially, a random association of the compounds occurred; however, the reaction progressed to yield a more structured, chelate type complex over time. NH4+from AMS effectively competed with calcium for complexation sites on the glyphosate molecule. Data suggest that the observed calcium antagonism of glyphosate and AMS reversal of the antagonism are chemically based.

Charge distributions and chemical effects. XL. Chemical bonds in benzenoid hydrocarbons

1986 ◽  
Vol 64 (2) ◽  
pp. 404-412 ◽  
Author(s):  
S. Fliszár ◽  
G. Cardinal ◽  
N. A. Baykara
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Atomic Charges ◽  
Chemical Bonds ◽  
Benzenoid Hydrocarbons ◽  
Average Deviation ◽  
Chemical Effects ◽  
Local Charge ◽  
Theoretical Results

Benzenoid hydrocarbons were examined using a bond energy scheme featuring the role of atomic charges. The latter were conveniently deduced from appropriate correlations between theoretical results and 13C nuclear magnetic resonance shifts. Atomization energies calculated in this manner agree with their experimental counterparts to within 0.36 kcal mol-1 (average deviation). It appears that benzenoid hydrocarbons can be efficiently described in terms of local charge density properties. In the absence of any distinctive specific feature characterizing benzenoids, this particular description of chemical bonds ultimately results in a unifying genealogy smoothly relating to one another the various possible types of CC and CH bonds which are formed by sp2 and sp3 carbons.

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