Simazine is a herbicide

Herbicide

Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...

 of the triazine

Triazine

A triazine is one of three organic chemicals, isomeric with each other, whose molecular formula is 333 and whose empirical formula is CHN.- Structure :...

 class. The compound is used to control broad-leaved weed

Weed

A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...

s and annual

Annual plant

An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...

 grasses.

Physical properties

• Water solubility
  Water solubility
  Water is a bent, polar compound and possesses the ability to Hydrogen bond. As a result, it has unique solubility characteristics as a solvent and functions differently at different temperatures.-Sources:...
  
  : 5 mg/L at 20 °C
• Solubility in other solvents: s. in methanol
  Methanol
  Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
  
  , chloroform
  Chloroform
  Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...
  
  , and diethyl ether
  Diethyl ether
  Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
  
   [6]; s.s. in pentane
  Pentane
  Pentane is an organic compound with the formula C5H12 — that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the n-pentane isomer; the other two being called...
  
  
• Vapor pressure
  Vapor pressure
  Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...
  
  : 0.000810 mPa at 20 °C
• Partition coefficient
  Partition coefficient
  In chemistry and the pharmaceutical sciences, a partition- or distribution coefficient is the ratio of concentrations of a compound in the two phases of a mixture of two immiscible solvents at equilibrium. The terms "gas/liquid partition coefficient" and "air/water partition coefficient" are...
  
  : 1.9600
• Adsorption coefficient: 130

Preparation

Simazine may be prepared in the laboratory from cyanuric chloride

Cyanuric chloride

Cyanuric chloride is the inorganic compound with the formula 3. This colorless solid is the chlorinated derivative of 1,3,5-triazine. It is the trimer of cyanogen chloride...

 crystals and a strong solution of ethyl amine (at least 50 percent by number in water). The reaction is highly exothermic

Exothermic

In thermodynamics, the term exothermic describes a process or reaction that releases energy from the system, usually in the form of heat, but also in the form of light , electricity , or sound...

 and is therefore best carried out in an ice bath below 10 °C. It is also essential to carry out the synthesis in a fume hood

Fume hood

A fume hood or fume cupboard is a type of local ventilation device that is designed to limit exposure to hazardous or noxious fumes, vapors or dusts. A fume hood is typically a large piece of equipment enclosing five sides of a work area, the bottom of which is most commonly located at a standing...

 since cyanuric chloride decomposes at high temperatures into hydrogen chloride

Hydrogen chloride

The compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...

 and hydrogen cyanide, both of which are highly toxic by inhalation.

Properties and uses

Simazine is an off-white crystalline compound which is sparingly soluble in water. It is a member of the triazine-derivative herbicides (see also atrazine

Atrazine

Atrazine, 2-chloro-4--6--s-triazine, an organic compound consisting of an s-triazine-ring is a widely used herbicide. Its use is controversial due to widespread contamination in drinking water and its associations with birth defects and menstrual problems when consumed by humans at concentrations...

), and was widely used as a residual nonselective herbicide, but is now banned in European Union states (EU directive 91/414/EEC). Like atrazine, it acts by inhibiting photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

. It remains active in the soil for 2-7 months after application.

Synthesis mechanism

This is the first part of the mechanism. It produces the product simazine and adds 4 equivalents of ethylamine instead of 2.

External links

• Pesticide Action Network http://pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC34340
• Extoxnet PIP http://extoxnet.orst.edu/pips/simazine.htm