Thermodynamic studies of monuron

Monuron (C9H11ClN2O; N,N-dimethyl-N'-(4-chlorophenyl) urea, CAS 150-68-5) was synthesized and the heat capacities of the compound were measured in the temperature range from 79 to 385 K with a high precision automated adiabatic calorimeter. No phase transition or thermal anomaly was observed in this range. The enthalpy and entropy data of the compound relative to the reference temperature 298.15 K were derived based on the heat capacity data. The thermodynamic properties of the compound were further investigated through DSC and TG analysis. The melting point, the molar enthalpy, and entropy of fusion were determined to be 447.6 +/- 0.1 K, 29.3 +/- 0.2 kJ mol(-1), and 65.4 J K-1 mol(-1), respectively. (C) 2004 Elsevier B.V. All rights reserved.

Effect of thiocarbamate, urea, and uracil herbicides on lipid metabolism in groundnut (Arachis hypogaea) leaves

The effect of thiocarbamates (S-ethyldipropylthiocarbamate and diallate), substituted ureas (monuron and diuron), and uracils (bromacil and terbacil) on lipid metabolism in groundnut (Arachis hypogaea) leaves was investigated under nonphotosynthetic conditions. The uptake of [1-14C]acetate by leaf disks was inhibited by the thiocarbamates and marginally by the substituted ureas, but not by the uracil herbicides. The uptake of [methyl-14C]choline was inhibited to a lesser extent by thiocarbamates, while the other herbicides showed a slight stimulation. The thiocarbamates almost completely inhibited uptake of [32P]orthophosphate at 1.0 mM concentration, while diuron and terbacil showed significant inhibition. [1-14C]Acetate incorporation into lipids was inhibited only by diallate. [methyl-14C]Choline incorporation into the choline phosphoglycerides was inhibited by diallate, diuron, and bromacil. The incorporation of [32P]orthophosphate into phospholipids was substantially inhibited (over 90% at 1.0 mM) by the thiocarbamates, but not by the other herbicides. [35S]Sulfate incorporation into sulfoquinovosyl diglycerides was markedly inhibited only by the thiocarbamates. Fatty acid synthesis by isolated chloroplasts was inhibited 40–85% by thiocarbamates, substituted ureas, and bromacil, but not by terbacil. The inhibitory effect of the urea derivatives was reversible, but that of thiocarbamates was irreversible. sn-Glycerol-3-phosphate acyltransferase(s) of the chloroplast and microsomal fractions were profoundly inhibited by thiocarbamates, but not by the other two groups of herbicides. Phosphatidic acid phosphatase was insensitive to all the herbicides tested.

Phenylurea herbicides-selective polymer prepared by molecular imprinting using N-(4-isopropylphenyl)-N'-butyleneurea as dummy template

A phenylurea herbicides-selective molecularly imprinted polymer (MIP) was prepared using N-(4-isopropylphenyl)-N'-butyleneurea as a dummy template and toluene as a porogen. The experimental results showed that the optimum molar ratio of template, functional monomer (MAA) and cross-linker (EDMA) was 1:8:20. Scatchard analysis showed that two classes of binding sites were formed in the imprinted polymer with dissociation constants of 26.81 mu L mol l(-1) and 1.428 mmol l(-1). The affinity and selectivity of MIP for phenylurea herbicides were studied. Among the 14 phenylurea herbicides tested, the MIP prepared showed obviously high affinity and selectivity for 10 chemicals (monuron, diuron, isoproturon, fenuron, chlortoluron, difenoxuron, metoxuron, neburon, buturon and fluometuron) with dichloromethane containing 10% hexane as mobile phase while non-imprinted polymer showed very low affinity for all the phenylurea herbicides tested. The experimental and calculated results also indicated that the size and property of the group at the N' position of phenylurea molecules have great influence on the affinity of MIP for them and the recognition site is mainly located at the N' position of phenylurea herbicides. (c) 2005 Elsevier B.V. All rights reserved.