Elsevier

Chinese Chemical Letters

Volume 26, Issue 8, August 2015, Pages 1008-1010
Chinese Chemical Letters

Original article
Design, synthesis and herbicidal activities of novel self-dispreading phenoxy carboxylic acid derivatives for the control of water hyacinth floating on the water surface

https://doi.org/10.1016/j.cclet.2015.04.008Get rights and content

Abstract

A series of novel self-dispreading phenoxy carboxylic acid derivatives were designed and synthesized by I2 catalyzed one-step reaction. Their structures were confirmed by IR, NMR, and HRMS. The derivatives can self-spread and float on the water surface. Preliminary bioassays showed that some compounds, 3i3p, had excellent herbicidal activities against water hyacinth. This strategy provided a novel approach for the water hyacinth control.

Graphical abstract

A series novel self-spreading phenoxy carboxylic acid derivatives were design and synthesized, which can float on the water surface and show excellent herbicidal activities against the water hyacinth.

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Introduction

Water hyacinth, which is considered to be the world's most troublesome foreign invasion species, has caused serious environmental problems and economic burdens in China [1]. In the absence of its natural enemies, the reproductive potential of this scourge is enormous. The rapid growth and reproduction of water hyacinth out-competes other plant species and forms dense floating mats, which may completely cover canals, rivers, and lakes [2]. In addition to direct harmful effects, such as impeding transport of irrigation and drainage of water, hindering navigation, contaminating fishing and aquaculture, and interfering with hydroelectric schemes, it also brings about some indirect negative effects, including the development of vectors or parasites [3]. Millions of dollars are spent on the control of the massive outbreak of the water hyacinth ever year in China [4].

Different management methods including manual salvage, herbicides and bio-controls, have been used to combat the exotic aquatic weeds. However, it is difficult to provide an effective control fundamentally by these traditional approaches [5], [6], [7]. Moreover, the water hyacinth's free-floating behavior makes it a very effective colonizer of newly invaded fresh water bodies. Although herbicides such as 2,4-dichlorophenoxy acetic acid (2,4-D), glyphosates, and paraquat have long been used in controlling water hyacinth and effectively reduced weed infestation, they also bring noticeable environmental pollution because herbicides must be applied throughout the entire body of water [8]. Self-spreading pesticides have been used in rice fields because of the advantages of high efficiency, safety, economy and labor reduction [9]. However, these pesticides were prepared by physical methods, and the active compounds easily precipitated from the water. Focusing on the control of water hyacinth according to its unique floating characteristics, we explored novel self-spreading highly active compounds derived from phenoxy carboxylic acids, which can float on the water surface and exhibit excellent herbicidal activities against water hyacinth at low surface concentration. Our original design strategy is outlined in Fig. 1.

Phenoxy carboxylic acids including 2,4-D possessed good herbicidal activities against water hyacinth in the previous studies [10], [11]. However, their drawbacks include intrinsic disadvantages like high density, water-insolubility and sedimentation. Ethylene glycols show hydrophilic nature and are does not ionize after being dissolved in water, and it can self-spread quickly and form surface films at the air–water interface [12]. In this study, in order to endow phenoxy carboxylic acids with the abilities of self-spreading and floating on the water surface, we synthesized phenoxy carboxylic acid derivatives being linked with different length ethylene glycols by I2 catalyzed one-step reaction (Scheme 1). The hydrophilic nature of ethylene glycols [13], [14], [15] and hydrophobic phenoxy carboxylic acids in the structure of synthesized compounds (3a3p) give the products excellent self-spreading and floating performance according to the theory of surfactants [16], [17]. Further experiments revealed that the floating derivatives kept high herbicidal activities for the water hyacinth at very low surface concentrations.

Section snippets

Experimental

All commercial reagents and solvents used for the reactions were commercially available and were used without further purification. Phenoxy carboxylic acids were purchased from TCI, and other chemicals used in the synthesis were of analytical grade. The infrared spectra were recorded on a Perkin-Elmer 1730 FT-IR spectrometer using KBr disks as stated. NMR spectra were obtained on a Bruker AVANCE 400 (400 MHz) spectrometer using tetramethylsilane as the internal standard and CDCl3 as the solvent.

Results and discussion

Compounds 3a3p were synthesized using I2 as catalyst by one-step reaction (Scheme 1). The starting materials, phenoxy carboxylic acids and ethylene glycols, are commercially available. The reaction was performed under mild conditions and afforded good to excellent isolated yields. The process provided a facile and effective approach to prepare the ester compounds.

The spreading speeds of the 3a3p were 4–10 cm/s and the areas were 125–380 cm2, respectively (Table 1). The spreading speeds showed

Conclusion

In summary, a series of novel self-spreading phenoxy carboxylic acid derivatives were designed and synthesized by I2 catalyzed one-step reaction. The derivatives can self-spread and float on the water surface. The bioassay activities results indicated that some target compounds, 3i3p, had excellent herbicidal activities against water hyacinth. These results were worthy for further study in the control of the other harmful aquatic organisms floating on the water surface.

Acknowledgments

This work was supported by the Advanced Research Team Project of Jiangxi Province (No. 20133BCB24011), Key Technology R&D Program of Jiangxi Province (No. 20141BBG70070) and Science Foundation of Jiangxi Provincial Department of Education (No. Gjj4669).

References (17)

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