Paraquat units

Two-fold Menschutkin reactions on 4,4 -bipyridine provide a route to compounds containing a redox-active paraquat unit [15]. Thus, reacting 54 with 6-to-syloxyhexyl thioacetate afforded 55 (Scheme 10.17). Perylene tetracarboxylic dii-mide presents another electron acceptor that has been functionalized with thiol end-groups. Thus, heating a mixture of the dianhydride 56 and 4-aminothiophe-nol (57) gave the product 58 (Scheme 10.18) [16],... 

The ability of electron-rich macromolecules 37 to act as donors to the electron-acceptor Paraquat 38 was investigated by means of H NMR and UV-Vis spectroscopies. A 1 1 mixture of 37 and 38 exhibited a broad CT band centered at 601 nm in addition to significant changes in the H-a and H-)3 chemical shifts in the Paraquat unit 38 <1999EJ03335>. 

Kim et al. reported a redox-driven molecular machine (Figure 46) based on a host-stabilized charge-transfer complex acting as a molecular loop lock. The molecular machine was based on a pseudorotaxane comprising a CB[8] ring and an axle component bearing a m-electron-deficient paraquat unit, a rr-electron-rich naphthalene unit. 

Nakashima et al. reported the first light-driven molecular shuttle based on a rotaxane (Figure 55) comprising an a-CD linked mechanically with an axle containing an azobenzene unit located at the center, two paraquat units at each side of the azobenzene unit, and 2,4-dinitrophenyl stoppers. The location of a-CD could be changed between the azobenzene and ethylene moieties by lights of different wavelengths or by the heat both in water and in DMSO. 

Union Carbide Corporation, 226, 251 Union Derivan SA (UNDESA), 203 Union Espanola de Explosivos SA, 203 Union Miniere N.V., 145 Uniqema, 210 Uniqema Eiternatiional, 196 UNIQUAT alklyl pyridines, 134 UNIQUAT , paraquat, 134 Uniroyal Chemical Co., 224, 251 Unisource India, 176 United Chemical Products Ltd., 198 United Chemical Technologies, 251... 

Figure 27 illustrates a rotaxane of Stoddart et al. [93], in which the axle contains two stations interacting with the cyclobis(paraquat-p-phenylene) bead. Its NMR spectrum at room temperature indicated that the bead moves back and forth like a shuttle between the stations about 1800 times a second. Stoddart et al. [94,95] prepared a [2]rotaxane containing two bipyridinium units and a crown, as shown in Fig. 28. The shuttling speed of the bead estimated by...

Paraquat is a broad-spectrum contact weed killer and herbage desiccant that is used widely in agriculture and horticulture. Paraquat was originally formulated in 1882, but its herbicidal properties were not discovered until 1955. Since its introduction in the early 1960s, paraquat has been used extensively in about 130 countries, including the United Kingdom, Canada, and the United States, on a wide variety of agricultural crops (Fletcher 1974 Haley 1979 Kelly et al. 1979 Anonymous 1988). 

Figure 10.5. Viabilities of D. vulgaris wild-type and Arbo strains following expo-snre to either air or air plus 10 pM paraquat. A, the surviving colony-forming units (CPUs) vs the times of either air or air plus paraquat exposure. B, The same data as percent survival of the air plus paraquat-exposed cells normahzed to the survivals of the air-exposed cells. The greater absolute survivals for the air-only exposed Arbo strain relative to wild type is an artifact due probably to the greater initial cell density used for the Arbo than for the wild-type strain in these experiments. Reprinted with permission from Lumppio et al. 2001, copyright 2001 American Society for Microbiology.

Decomposition of farm-generated pesticide wastewater was demonstrated with a mobile 66-lamp ultraviolet (UV) unit and ozone. Aqueous solutions of 2,4-D (1086 ppm) and atrazine (4480 ppm) were degraded more than 80% in about 2-3 h, while paraquat (1500 ppm) was degraded more slowly. 

Dwell time, or the time the molecule was actually in the lamp unit, and concentration were two parameters that affected the rate of degradation. Mass spectra of the trimethylsilyl (TMS) derivatives of atrazine subjected to UV-ozonation revealed a number of dehalogenated, dealkylated s -triazines, paraquat yielded the 4-picolinic acid, and 2,4-D gave oxalic acid, glycolic acid and several four-carbon oxidation products. The economics of UV-ozonation as a pretreatment for land disposal compares favorably with incineration and other options open to the small pesticide user. 

Figure 12. Degradation of paraquat via UV-ozonation at 1500 ppm in the 66-lamp unit.

Paraquat and the related chemical diquat are nonselective herbicides that are also toxic to mammals. Occupational or accidental exposure to paraquat can be from oral ingestion, dermal exposure, or inhalation, all of which can cause serious illness or death. While seldom used in the United States, paraquat is still widely used in developing countries. At one time it was used to kill marijuana plants, but a number of fatalities were observed when marijuana contaminated with paraquat was inhaled. 

The [2]rotaxanes, which contain tetrathiafulvalene (TTF) and 1,5-dioxynaphtha-lene (DNP) as the two recognition stations and cyclobis(paraquat-p-phenylene) (CBPQT4 + ) as the cyclic moiety, have been comprehensively investigated by Stoddart and coworkers.68 We have recently reported two new TTF-DNP-CBPQT4+ [2]rotaxanes 62 and 63. In these two [2]rotaxanes, the TTF moiety is the 4,4 (5 )-dialkylthiotetrathiafulvalene that is rather easily accessible based on the synthetic procedure developed by us previously,69 and two different spacers are used the cyclohexyl and alkyl chains. Two stopper units are the G2-dendritic moieties. 

Until the mid-1990s, multiple-resistance (i.e., resistance to more than one herbicide mode of action within the same biotype) had not been reported within North America. However, Foes et al. (1996) found a kochia biotype from western Illinois resistant to atrazine and several ALS-inhibiting herbicides. Lopez-Martinez et al. (1996) reported that a triazine-resistant Echinochloa species found in atrazine-treated com also showed cross-resistance to quinclorac. Clay and Underwood (1989) and Clay (1989) reported that one triazine-resistant biotype of American willowherb was also resistant to paraquat from a hop garden in the United Kingdom treated annually for 25 years with simazine and paraquat. 

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