Anna Syguda

Herbicidal Ionic Liquids with 2,4-D

Abstract Three herbicidal ionic liquids (HILs)—alkyldi(2-hydroxyethyl)methylammonium (2,4-dichlorophenoxy)acetate, dialkyldimethylammonium (2,4-dichlorophenoxy)acetate, and alkyltrimethylammonium (2,4-dichlorophenoxy)acetate—were synthesized and their activity against broad-leaved weeds was investigated under field conditions. HILs as [cation][2,4-D] used in winter wheat were much more active compared to 2,4-D-dimethylammonium salt and demonstrated efficacy similar to 2,4-D 2-ethylhexyl ester. HILs exhibited desirable surface properties such as low contact angle of droplets and low surface tension. Moreover, the HILs may be safer to operators and neighboring plants due to their nonvolatile nature. HILs at 450 g ha−1 of 2,4-D did not injure wheat. Nomenclature: Alkyldi(2-hydroxyethyl)methylammonium (2,4-dichlorophenoxy)acetate; dialkyldimethylammonium (2,4-dichlorophenoxy)acetate; alkyltrimethylammonium (2,4-dichlorophenoxy)acetate.

Ionic liquid forms of the herbicide dicamba with increased efficacy and reduced volatility

Twenty eight new dicamba (3,6-dichloro-2-methoxybenzoic acid)-based herbicidal salts, have been synthesized and characterized in order to attempt to improve the efficacy of this widely known herbicide used to protect maize, grassland, and other cultures. The new compounds, most of which are ionic liquids by definition and three of which are solids melting above 100 °C, were prepared by pairing quaternary tetraalkyl- or alkoxyammonium, piperidinium, imidazolium, pyridinium, morpholinium, quinolinium, and phosphonium cations with the dicamba anion. Growth chamber and field test data suggested that ionic liquid forms of dicamba offer substantially increased efficacy which would allow less to be applied in the field. Compared to the commercial dicamba free acid product, improved physical properties were observed including higher decomposition temperatures and reduced volatilities, suggesting a potential reduction of overall environmental impact of this herbicide.

Influence of oligomeric herbicidal ionic liquids with MCPA and Dicamba anions on the community structure of autochthonic bacteria present in agricultural soil

The aim of this study was to evaluate the impact of selected herbicidal ionic liquids (HILs), which exhibit high efficacy in terms of weed control and low toxicity, but may be persistent due to limited biodegradability, on the community structure of autochthonic bacteria present in agricultural soil. Four different oligomeric HILs (with two types of cations and different ratio of herbicidal anions) were synthesized and characterized by employing (1)H and (13)C NMR. The results of biodegradation assay indicated that none of the tested HILs could be classified as readily biodegradable (biodegradation rate ranged from 0 to 7%). The conducted field studies confirmed that the herbicidal efficacy of the HILs was higher compared to the reference herbicide mixture by 10 to 30%, depending on the dose and weed species. After termination of field studies, the soil treated with the tested HILs was subjected to next generation sequencing in order to investigate the potential changes in the bacterial community structure. Proteobacteria was the dominant phylum in all studied samples. Treatment with the studied HILs resulted in an increase of Actinobacteria compared to the reference herbicidal mixture. Differenced among the studied HILs were generally associated with a significantly higher abundance of Bacteroidetes in case of 1-HIL-Dicamba 1/3 and Firmicutes in case of 2-HIL-Dicamba 1/3.

Toxicity of synthetic herbicides containing 2,4-D and MCPA moieties towards Pseudomonas putida mt-2 and its response at the level of membrane fatty acid composition.

One of the attempts to create more effective herbicidal compounds includes the use of ionic liquids. Herbicidal ionic liquids have more effective biological activity, they are less volatile, more thermally stable, and exhibit superior efficiency in comparison to typically employed herbicides, allowing the reduction of the herbicide dose applied per hectare. However, studies on the environmental toxicity of this group of compounds are very rarely available. Environmental toxicity is an important factor, showing the concentration of compounds that has negative effects on soil bacteria including those responsible for biodegradation processes. Therefore, potential toxicity of four herbicidal ionic liquids (HILs) precursors containing 2,4-D and MCPA moieties was tested with the well investigated model organism for toxicity and adaptation, Pseudomonas putida mt-2. Results were compared to those obtained for commercial 2,4-D and MCPA herbicides. Next to growth inhibition, given as EC50, changes in the isomerisation of cis to trans unsaturated fatty acids were applied as proxy for cellular stress adaptation to toxic substances. The results revealed that all investigated precursors of HILs showed lower toxicity compared to commercialized synthetic herbicides 2,4-D and MCPA. The collected data on toxicity of HILs together with their physico-chemical properties might be useful for assessing the potential risk of the environmental pollution as well as guidelines for setting the legislation for their future use.

Pyrrolidinium herbicidal ionic liquids

In this work, sixteen new pyrrolidinium herbicidal ionic liquids (HILs) with phenoxycarboxylate anions were synthesized and characterized. The effect of the alkyl or alkoxymethyl chain length and type of anion on the physicochemical properties, such as density, viscosity and refractive index of HILs, as well as on the thermal stability and surface activity, were determined. The oxygen presence in the structures of the prepared HILs significantly affects their thermal and surface properties. Furthermore, the herbicidal efficacy was tested in greenhouse experiments by using common lambsquarters (Chenopodium album L.) as a test plant. The novel pyrrolidinium ionic liquids were more effective than the commercial herbicides.

Ionic liquids - deanol derivatives as the Diels-Alder reaction solvents

AbstractThe Diels-Alder reaction between cyclopentadiene and dienophiles in deanol derivatives containing bis(trifluoromethylsulfonyl)imide anion as media have been studied. The effect of the substituents attached to the cation on the endo:exo selectivity as well as the reaction yield have been evaluated in the absence and presence of Lewis acid catalyst - Y(OTf)3. Catalytic activity of metal triflates and the recycling of chosen catalytic systems have also been investigated

Effects of ammonium-based ionic liquids and 2,4-dichlorophenol on the phospholipid fatty acid composition of zebrafish embryos

Ionic liquids consisting of a combination of herbicidal anions with a quaternary ammonium cation act as efficient herbicides, which are under consideration to be used in the agriculture. In the present study, we used embryos of the zebrafish (Danio rerio) as a model to assess the toxic potential of ammonium-based ionic liquids for aquatic organisms. As we assumed interference of the partially hydrophobic ionic liquid cation with lipids, we investigated the adaptation response in the lipid composition of the zebrafish embryos, triggered by the ionic compound. Therefore, the impact of ammonium-based ionic liquids with different lengths of the alkyl chain ([C6,C6,C1,C1N][Br], [C8,C8,C1,C1N][Br]) on the phospholipid fatty acid (PLFA) profile of zebrafish embryos up to 72 hours post fertilization (hpf) was examined. Furthermore, the changes in the unsaturation index (UI) of PLFAs, as the sum parameter of membrane fluidity in eukaryotic cells, were presented. The PLFA’s UI in the zebrafish embryos upon exposure to quaternary ammonium salts was compared to the UI of the embryos upon exposure to nonionic 2,4-dichlorophenol, which has a similar hydrophobicity but is structurally different to [C8,C8,C1,C1N][Br]. It was shown that for ammonium-based ionic liquid precursors non-specific mode of action occurs and the toxic effect on lipid composition of zebrafish embryos can be well predicted based on chemical properties, like hydrophobicity. Furthermore, the changes in PLFAs, expressed by the UI, can be useful to study toxic effects of organic contamination. However, for zebrafish embryos, after ionic liquids and 2,4-DCP exposure, the changes were observed at high lethal concentrations, which caused the incidence of lethality of 30 and 50% of a group of test animals.

Esterquat herbicidal ionic liquids (HILs) with two different herbicides: evaluation of activity and phytotoxicity

Herbicidal ionic liquids (HILs) constitute a new concept in crop protection products. Their main advantage is the potential to combine the efficiency of traditional herbicides with low vapour pressure and adjustable water solubility which leads to improved environmental safety in the agricultural sector. Among many strategies to obtain new HILs, esterquats seem to be well suited for modification since both the cation and anion may be constituents of herbicides. In the framework of this study 16 new esterquat HILs were synthetized based on standard herbicides: 2,4-D, MCPA, MCPP, 4-CPA, Clopyralid and Dicamba. Germination tests performed on agricultural soil using cornflower indicated the best two HILs. Furthermore, analysis of the toxicological effects of HILs on wheat plants revealed an additional advantage of the two selected HILs. The glutathione (GSH) content and glutathione S-transferase (GST) activity showed a lower oxidative stress level in wheat plants treated with examined HILs, respectively, in comparison to a mixture of reference compounds. Finally the Ames test was applied in order to analyse the mutagenic activity of the two selected HILs.