Herbicidal activities

Some essential oils are not only insecticidal but also possess strong phytotoxic effects. In many cases, this would be considered a serious drawback to the use of these essential oils for insect pest control however, this also opens the door to the use of some oils as herbicides. Although few studies have addressed this herbicidal activity, work completed by Tworkoski [25] demonstrated that the 

Besides the direct use as herbicides, one specific use of phytotoxic essential oils could be for chemical thinning of fruit trees. In initial trials with a commercially available clove oil-based herbicide (Matran, produced by EcoS MART Technologies Inc), apple blossom thinning effects were observed however, extensive leaf and fruit russeting was also observed, with effects dependent on concentration and the apple cultivar tested [27]. While the initial results are promising, further studies will be required before such herbicides can be used as chemical thinning agents. 

---

Glyphosate was first prepared in 1950, in Switzerland (29), but its potent herbicidal activity was not disclosed until 1970 by Monsanto Chemical Co. 

Thiosemicarbazides are useful in forming 1,3,4-thiadiazoles, a class of compounds having herbicidal activity. 

Dehydiation with POCl, followed by N-alkylation with isobutylene, gives the cyano ester intermediate, which on treatment with methylamine yields (64), a compound having good herbicidal activity (eq. 15). 

Before the discovery of streptomycin, pyrazinamide (126) was one of the front runners in the treatment of tuberculosis. A broad spectrum of biological activity has been associated with pyrazine derivatives, ranging from the herbicidal activity of (127) to antibiotic activity... 

Oxadiazines herbicidal activity, 3, 1085 reactions with bases, 3, 1060 ring contraction, 3, 1065 ring opening, 3, 1061... 

Oxadiazole, 2,5-diaryl-electrophilic substitution, 6, 438 as fluorescent whitener, 6, 446 herbicidal activity, 6, 445... 

Pyrimido[4,5-d]pyrimidin-4(3H)-one, 2,5,7-trialkyl-herbicidal activity, 3, 368 Pyrimido[ 1,2-a ]pyrimidin-2-ones hydrobromide H NMR, 3, 337 UV spectra, 3, 338 Pyrimido[ 1,2-a]pyrimidin-4-ones... 

Mecoprop is also found frequently in surface freshwaters. MAFF have recognized this and taken action. Mecoprop is a mixture of two different chemical forms, only one of which has herbicidal activity. Historically, products contained a mixture of both forms, resulting in the need for high doses to achieve the desired effect. However, it is now possible to separate the herbicidally active form... 

Chemical Tastes (Other) Pesticides-herbicides Activated carbon filter will absorb limited amount. Must continue to monitor the product water closely... 

Thiazolo[2,3-c][l,2,4]triazines 658 were prepared (84LA1302) regio-specifically by cyclizing 2-hydrazono-2-thiazoline 659 with glyoxylic acid or ester. They had herbicidal activity. Condensation of 659 with oxamic acid ethyl ester gave hydrazide 660, which was cyclized with sodium... 

The herbicide activity ascribed to the 1,2,4-oxadiazole derivative 67 (60) has prompted the search for other biologically active derivatives. This example was prepared from the corresponding 5-chloromethyl-1,2,4-oxadiazole 63 via conversion to the HHT 65 through the aminomethyl analog 64. Reaction of the HHT 65 with diethyl phosphite under neat conditions produced the desired diethyl ester intermediate 66, which was hydrolyzed to 67. 

It was not until 1962 that the first quantitative structure-activity relationship was published by Corwin Hansch and co-workers [13], relating to the herbicidal activity of a series of phenoxyacetic acids ... 

Natural systems may be quite complex. For example, the enantiomerization of phenoxyalkanoic acids containing a chiral side chain has been studied in soil using H20 (Buser and Muller 1997). It was shown that there was an equilibrium between the R- and 5-enantiomers of both 2-(4-chloro-2-methylphenoxy)propionic acid (MCPP) and 2-(2,4-dichlorophenopxy)propionic acid (DCPP) with an equilibrium constant favoring the herbicidally active / -enantiomers. The exchange reactions... 

Acylanilides (abbreviated as anilides in this article) are generally used as selective pre- and/or post-emergence herbicides in paddy rice fields. The herbicidal activity of the anilides is similar to those exhibited by the auxin-like plant growth regulators. 

---