Blog Archive

Tuesday, April 19, 2022

04-19-2022-0451 - Thidiazuron

Thidiazuron (TDZ) is an herbicide.

Thidiazuron
Thidiazuron structuur.png
Names
IUPAC name
1-Phenyl-3-(1,2,3-thiadiazol-5-yl)urea
Other names
TDZ
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard100.052.125 Edit this at Wikidata
EC Number
  • 257-356-7
Properties
C9H8N4OS
Molar mass220.25 g·mol−1
AppearanceWhite powder
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Applications[edit]

Plant growth regulator[edit]

The synthesis routes and their use as plant growth regulating agent were patented in the early 1980s by the German company Schering AG. The substance is taken up by the leaves and has a cytokinin-like behavior. It causes leaves to lose weight in a controlled manner prior to harvesting, without affecting the growth and maturation of the plant. This facilitates mechanical harvesting. It also accelerates the maturation process, because leaves do not block the sunlight. The plants later develop normal foliage. Thidiazuron can also be used as a herbicide, because an appropriate dose and timing of administration completely stops growth.[citation needed]

The product was marketed by Aventis CropScience; later merged into Bayer CropScience. Brand names are Dropp (for use in the cultivation of cotton) or Revent (for use in fruit production). Dropp Ultra, Dropp UltraMax and Ginstar are products with a mixture of thidiazuron and diuron.

Preservative[edit]

Researchers found that thidiazuron is suitable for extending the life of cut flowers. The substance slows down or prevents the wilting of the leaves.

Regulatory[edit]

European Union[edit]

In 2008 the European Union banned the use of thiadiazuron in agriculture. It was one of the agricultural chemicals in the framework of the European Pesticides Directive 91/414 / EEC that must have an environmental and health assessment to obtain a new authorization.[1] An outdated substance is an active substance which was already on the market in the European Union on July 25, 1993, before the action step of the directive. Existing stocks could still be used afterwards for one year.[1] Thidiazuron is still used in other parts of the world, including in the United States, Australia and Mexico.[citation needed]

Toxicology and safety[edit]

Thidiazuron is mildly acutely toxic, irritating to skin and eyes, and may cause respiratory irritation if inhaled.[2]

https://en.wikipedia.org/wiki/Thidiazuron

04-19-2022-0449 - defoliant

 defoliant is any herbicidal chemical sprayed or dusted on plants to cause their leaves to fall off. Defoliants are widely used for the selective removal of weeds in managing croplands and lawns. Worldwide use of defoliants, along with the development of other herbicides and pesticides, allowed for the Green Revolution, an increase in agricultural production in mid-20th century.[1] Defoliants have also been used in warfare as a means to deprive an enemy of food crops and/or hiding cover, most notably by the United Kingdom during the Malayan Emergency and the United States in the Vietnam War. Defoliants were also used by Indonesian forces in various internal security operations.[2]

Use and application[edit]

A primary application of defoliants is the selective killing of plants. Two of the oldest chemical herbicides used as defoliants are 2,4-Dichlorophenoxyacetic acid (2,4-D) and 2,4,5-Trichlorophenoxyacetic acid (2,4,5-T). 2,4-D and 2,4,5-T are absorbed by broad-leafed plants, killing them by causing excessive hormonal growth.[1] These phenoxy herbicides were designed to selectively kill weeds and unwanted plants in croplands. They were first introduced at the beginning of World War II and became widespread in use in agriculture following the end of the War.

Defoliants have a practical use in the harvesting of certain crops, particularly cotton, in the United States as well as a number of other cotton-producing countries. The use of defoliants aids in the effective harvesting of cotton and finer lint quality.[3] The effectiveness of defoliant use in cotton harvesting depends on the type of defoliant(s) used, the number of applications, the amount applied, and environmental variables. Common harvest-aiding chemical defoliants include tribufos, dimethipin, and thidiazuron. According to a 1998 report by the U.S. Department of Agriculture National Agricultural Statistics Service (NASS), tribufos and thidiazuron accounted for 60% of crop area that was treated by defoliants during that crop year.[4][5]

https://en.wikipedia.org/wiki/Defoliant


04-19-2022-0448 - 6058/9-60,1-2

 04-19-2022-0448 - 6058/9-60,1-2

04-19-2022-0447 - crop desiccation

 Pre-harvest crop desiccation refers to the application of an agent to a crop just before harvest to kill the leaves and/or plants so that the crop dries out from environmental conditions ("dry-down") more quickly and evenly.[1][2][3] In agriculture, the term desiccant is applied to an agent that promotes dry down, thus the agents used are not chemical desiccants, rather they are herbicides and/or defoliants used to artificially accelerate the drying of plant tissues.[4] Desiccation of crops through the use of herbicides is practiced worldwide on a variety of food and non-food crops.

Active agents[edit]

In agricultural parlance, desiccation is divided into two distinct groups: "true desiccants" and pre-harvest systemic herbicides.[14][15] True desiccants are not chemical desiccants, rather they are contact herbicides which kill only the parts of the plant they touch. They induce plant death/defoliation rapidly and dry down occurs within a few days. True desiccants do not often provide good weed control because killing only the top growth may allow plants to begin re-growing again. In contrast, systemic herbicides are absorbed by foliage or roots and translocated to other parts of the plant. They poison metabolism throughout the plant thus the process is slower, with die off and dry down taking up to a couple weeks.

"True desiccants"[edit]

Most of these kinds of contact herbicides are cell membrane disruptors that are either "PPO inhibitors" or "Photosystem I inhibitors." Plant cells have chloroplasts, which contain the protoporphyrinogen oxidase (PPO) enzyme complex. PPO inhibitors poison that enzyme, causing a build up of Protoporphyrin IX (Proto). Normally Proto is present in very low amounts, but when there is too much Proto it interacts with light to form singlet oxygen radicals (1O2). These interact with the fatty acids of membranes, causing disruption of membrane integrity and leakage of cell contents. The plants soon begin to wilt and quickly dry out in the sun. Plants can burn within hours of exposure to these herbicides.[16] In contrast, Photosystem I inhibitors such as Diquat and paraquat work by entering plant cells and immediately diverting electrons away from photosynthetic chain, poisoning photosynthesis. In addition, hydroxyl radicals (•OH) are formed which interact with the fatty acids of membranes, causing disruption of membranes, leakage, plant wilting, and drying out in the sun.[17]

Contact herbicides used for desiccation include: carfentrazone-ethyl, cyclanilide, diquat, endothallglufosinate, paraquat, pelargonic acid / ammonium nonanoate, pyraflufen-ethyl, saflufenacilsodium chloratethidiazuron, and tribufos. [1][5][4][7][11] The most common and widely used contact desiccant is diquat (Reglone®).

For potatoes, sulfuric acid is sometimes used as a non-herbicide chemical desiccating agent.[18]

Systemic desiccants (glyphosate)[edit]

Glyphosate (Roundup®) is the principal pre-harvest systemic herbicide used for desiccation of a wide variety of crops. As a systemic herbicide it is not a true desiccant as it can take weeks rather than days for the crop to die back and dry out after application.[15][19]

Glyphosate works by poisoning the shikimate pathway which is found in plants and microorganisms but not in animals. Specifically, it inhibits the EPSP synthase enzyme which is required for plants to make certain amino acids.[20] Without these, metabolism in the plant collapses. In addition, shikimate accumulates in plant tissues and diverts energy and resources away from other processes, eventually killing the plant over a period of days to weeks.

In the UK, glyphosate began to be applied to wheat crops in the 1980s to control perennial weeds such as common couch which was very effective and meant that sowing of the next crop could occur sooner. Use as a harvest aid in the UK increased after the introduction of strobilurin fungicides which prolong the longevity of the leaves,[21] and by 2002, 12% of UK wheat crops were treated in this way.[22]

The timing of application is crucial as the moisture content of the grain must be below 30% for the yield of the crop to be unaffected and to minimize uptake of glyphosate by the grain.[23] Yield may be affected and residues increased if applications are made to uneven fields in which some areas have a moisture content over 30%. Although used in weed-free and evenly maturing crops with the aim of reducing the grain moisture content more rapidly to hasten the harvest, there is little or no advantage in doing so.[21]

The application of glyphosate differs between regions and countries significantly. In North America, for example, its use on wheat crops is uncommon in the United States but more common in Canada which has a colder climate and shorter growing season. In the UK where summers are wet and crops may ripen unevenly 78% of oilseed rape is desiccated before harvest, but only 4% in Germany.[24]

Questions over practice[edit]

Herbicide residue in food has been raised as a concern. Residue quantities are regulated by Codex Alimentarius of the Food and Agriculture Organization of the United Nations.[25]

In July 2013 Austria banned the use of pre-harvest glyphosate citing the precautionary principle.[26] In April 2015 an oat buyer in Western Canada announced that it was refusing oats in which pre-harvest glyphosate had been used.[27][28]

Glyphosate was found in 5–15% of cereal crop samples tested in the UK between 2000 and 2004, although never exceeding the Maximum Residue Level of 20 mg/kg.[22] A survey of British wheat in 2006-2008 found average levels of 0.05–0.22 mg/kg with maximum levels of 1.2 mg/kg.[29]

https://en.wikipedia.org/wiki/Crop_desiccation


04-19-2022-0446 - Glyphosate Glyphosate-based herbicides Glufosinate

Glyphosate (IUPAC nameN-(phosphonomethyl)glycine) is a broad-spectrum systemic herbicide and crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase. It is used to kill weeds, especially annual broadleaf weeds and grasses that compete with crops. Its herbicidal effectiveness was discovered by Monsanto chemist John E. Franz in 1970. Monsanto brought it to market for agricultural use in 1974 under the trade name Roundup. Monsanto's last commercially relevant United States patent expired in 2000.

https://en.wikipedia.org/wiki/Glyphosate

John E. Franz (born December 21, 1929) is an organic chemist who discovered the herbicide glyphosate while working at Monsanto Company in 1970.[1] The chemical became the active ingredient in Roundup, a broad-spectrum, post-emergence herbicide. Franz has earned much acclaim and many rewards for this breakthrough. He also has over 840 patents to his name worldwide.

Discovery of glyphosate[edit]

Researchers at Monsanto had been searching for an herbicide that was effective against annual and perennial weeds for nine years but found little success. They knew of two phosphonic acid compounds that were ineffective against weeds, and the researchers were not able to advance the compounds. Franz took over the research in 1969 and incorrectly hypothesized that the phosphonic acids acted as proherbicides that were metabolized to active compounds rather than herbicides. Franz and his research team screened possible metabolites and synthesized compounds and eventually discovered glyphosate in 1970.[2]

Although all of the patents regarding glyphosate list Franz as the sole inventor and the Monsanto Company as the assignee, Franz acknowledged that the discovery was a group effort. In 2007, when he was inducted into the National Inventor's Hall of Fame, Franz said, "It's a recognition of the entire team of scientists who worked on and supported the development of Roundup herbicides".[5] Glyphosate works by absorption through leaves, and then moving rapidly to a plant's roots, rhizomes, and meristems. This invaluable breakthrough immediately spurred Monsanto to design and produce plants genetically immune to glyphosates in order to make it easier for farmers to thoroughly spray down their fields for weeds without killing their own crops.[6]

Once glyphosate was invented, it took four years to reach the market. It was first introduced as "Roundup", and is still best known by that brand.[2]

Glyphosate has been called by experts in herbicides "virtually ideal" due to its broad spectrum and low toxicity compared with other herbicides.[6][7][8] However, the chemical’s use has come under attack in numerous countries, with bans or partial bans enacted, and thousands of lawsuits filed alleging the chemical is carcinogenic. German Chancellor Angela Merkel stated in June 2019 “We will come to a point where glyphosate isn’t used anymore.” [9]

Other research[edit]

Franz undertook research in many areas during his time at Monsanto. Some of his other chemistry research includes antiauxin chemistry (isothiazoles, isoxazoles, pyrazoles), plant chemistry, cell membrane chemistry (glyceride and phospholipid syntheses, liposomes), plant hormone chemistry (abscissic acid analogs, ethylene generators), and nitride sulfide chemistry. He also performed research pertaining to reaction mechanisms, coenzyme A antimetabolites, biorational design of herbicides, and periselective addition reactions of one- and threedipoles, as well as fundamental organic research.[3]

Honors[edit]

Franz has received many awards for his important discovery. In 1977, he was awarded the IR-100 award by Industrial Research magazine. In 1981, he received the first J.F. Queeny Award from Monsanto to honor an invention that was also a commercial success. He was the recipient of the 1987 National Medal of Technology, one of the few agricultural technologies to ever receive the honor. Franz received the American Chemical Society’s Carothers Award in 1989 for "outstanding contributions and advances in industrial applications of chemistry". In 1990, he was awarded the Perkin Medal by the American Section of the Society of Chemical Industry, based on his contributions to the research and development of applied chemistry. Franz also won the Outstanding Achievement Award in 1988, the 1988 Missouri Award, and was named the St. Louis Metropolitan Bar Association Inventor of the Year in 1986. Roundup was named one of the "Top 10 Products That Changed the Face of Agriculture" by the magazine Farm Chemicals in 1994. Franz was inducted into the United States' Inventor's Hall of Fame on May 5, 2007.[2][10][11]

Monsanto has also created two awards in his honor. On December 8, 1995, the agricultural company introduced the Franz Sustainability Award, which consists of an annual $100,000 prize given to the individual or team that submits the best environmental project for improvement in the areas of conservation, technology, and/or education.[12] Soon after Franz's induction into the Inventors' Hall of Fame in 2007, Monsanto announced a new annual scholarship called the Franz Innovation Award Scholarship. This scholarship is awarded each year to a graduate student taking organic chemistry at the University of Minnesota.[13]

Patents[edit]

Franz has over 840 patents to his name concerning glyphosate and lesser known discoveries. Because of the nature of glyphosate, it requires many patents concerning identification, synthesis, and other processes required to produce the chemical.[14]

His patents include:[15]

  • Patent Number: 3799758, Phytotoxicant compositions[1]
  • Patent Number: 3853530, Regulating plants with n-phosphonomethylglycine and derivatives thereof[16]
  • Patent Number: 3977860, Herbicidal compositions and methods employing esters of[17]
  • Patent Number: 3954848, Process for producing N-phosphonomethy glycine[18]
  • Patent Number: 4735649, Gametocides[19]
  • Patent Number: 4634788, Herbicidal glyphosate oxime derivatives[20]
  • Patent Number: 4094661, Plant Growth Regulators[21]

https://en.wikipedia.org/wiki/John_E._Franz

Glyphosate-based herbicides are usually made of a glyphosate salt that is combined with other ingredients that are needed to stabilize the herbicide formula and allow penetration into plants. The glyphosate-based herbicide Roundup was first developed by Monsanto in the 1970s. It is used most heavily on cornsoy, and cotton crops that have been genetically modified to be resistant to the herbicide. Some products include two active ingredients, such as Enlist Duo which includes 2,4-D as well as glyphosate. As of 2010, more than 750 glyphosate products were on the market. The names of inert ingredients used in glyphosate formulations are usually not listed on the product labels.

Glyphosate and glyphosate-based herbicides have low acute toxicity in mammals. They likewise have not been shown to pose a significant risk to human health during normal use, although human deaths have been reported from deliberate ingestion of concentrated RoundUp. It is difficult to determine how much surfactants contribute to the overall toxicity of each formulation. Glyphosate formulations containing the surfactant polyethoxylated tallow amine (POEA) are sometimes used terrestrially, but are not approved for aquatic use in the US due to their toxicity to aquatic organisms.

There have been multiple lawsuits against Monsanto asserting that exposure to glyphosate herbicides is carcinogenic and that the company did not adequately disclose the risk to consumers. In 2018 a California jury awarded $289 million in damages (later cut to $78 million on appeal[1] then reduced to $21 million after another appeal[2]) to a groundskeeper who argued that Monsanto failed to adequately warn consumers of cancer risks posed by the herbicides.[3]

https://en.wikipedia.org/wiki/Glyphosate-based_herbicides

Glufosinate (also known as phosphinothricin and often sold as an ammonium salt) is a naturally occurring broad-spectrum herbicide produced by several species of Streptomyces soil bacteria. Glufosinate is a non-selective, contact herbicide, with some systemic action.[1] Plants may also metabolize bialaphos, another naturally occurring herbicide, directly into glufosinate.[2] The compound irreversibly inhibits glutamine synthetase, an enzyme necessary for the production of glutamine and for ammonia detoxification, giving it antibacterialantifungal and herbicidal properties. Application of glufosinate to plants leads to reduced glutamine and elevated ammonia levels in tissues, halting photosynthesis and resulting in plant death.[3]

https://en.wikipedia.org/wiki/Glufosinate


04-19-2022-0442 - Phosphonates or phosphonic acids

Phosphonates or phosphonic acids are organophosphorus compounds containing C−PO(OH)2 or C−PO(OR)2 groups (where R = alkylaryl). Phosphonic acids, typically handled as salts, are generally nonvolatile solids that are poorly soluble in organic solvents, but soluble in water and common alcohols. Many commercially important compounds are phosphonates, including glyphosate (the active molecule of the herbicide "Roundup"), and ethephon, a widely used plant growth regulator. Bisphosphonates are popular drugs for treatment of osteoporosis.[1]

Clodronic acid is a bisphosphonate used as a drug to treat osteoporosis.

In biology and medicinal chemistry, phosphonate groups are used as stable bioisoteres for phosphate, such as in the antiviral nucleotide analog, Tenofovir, one of the cornerstones of anti-HIV therapy. And there is an indication that phosphonate derivatives are "promising ligands for nuclear medicine."[2] 




https://en.wikipedia.org/wiki/Phosphonate


04-19-2022-0441 - Carbonate-hosted lead-zinc ore deposits

 Carbonate-hosted lead-zinc ore deposits are important and highly valuable concentrations of lead and zinc sulfide ores hosted within carbonate (limestonemarldolomite) formations and which share a common genetic origin.

https://en.wikipedia.org/wiki/Carbonate-hosted_lead-zinc_ore_deposits