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United States Department of Agriculture

Agricultural Research Service

Title: Nmr Relaxation Study on Acetamide Pesticide Interactions with Soil Organic Matter Surrogates

Authors
item Jayasundera, Shalini - UMD
item Schmidt, Walter
item Hapeman, Cathleen
item Torrents, Alba - UMD

Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 15, 1999
Publication Date: N/A

Technical Abstract: The dynamics of acetamide pesticide interactions between metolochlor or acetanilide as a probe compound and soil organic matter (OM) surrogates were studied using Nuclear Magnetic Resonance Spectroscopy. The 13 C and 1H relaxation times were measured to investigate and identify the specific sites within the ligand and substrate molecules at which interactions occurred. T1 and T2 relaxation times were determined as a function of the colloidal OM concentration. Decrease in T1 at specific sites of acetamide molecules, with OM concentration was a function of the properties of the OM. The rate of decrease in T1 when interacting with the less polar lignin was larger than with the more polar cellulose. Changes in relaxation were correlated to calculated and experimentally determined binding coefficients (K(oc)). NMR parameter changes at specific sites together with experimentally determined thermodynamic parameters suggests that acetamide pesticides form weak hydrophobic interactions with lignin and more specifi and relatively stronger hydrogen bonding type interactions with chitin and cellulose.

Last Modified: 7/23/2014
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