{{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 464391754 | ImageFile = Simazine.svg | ImageSize = 200px | ImageAlt = Skeletal formula of simazine | ImageFile1 = Simazine-3D-spacefill.png | ImageAlt1 = Space-filling model of simazine | PIN=6-Chloro-''N''<sup>2</sup>,''N''<sup>4</sup>-diethyl-1,3,5-triazine-2,4-diamine | OtherNames= |Section1={{Chembox Identifiers | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 5027 | InChI = 1/C7H12ClN5/c1-3-9-6-11-5(8)12-7(13-6)10-4-2/h3-4H2,1-2H3,(H2,9,10,11,12,13) | InChIKey = ODCWYMIRDDJXKW-UHFFFAOYAN | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/C7H12ClN5/c1-3-9-6-11-5(8)12-7(13-6)10-4-2/h3-4H2,1-2H3,(H2,9,10,11,12,13) | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = ODCWYMIRDDJXKW-UHFFFAOYSA-N | CASNo_Ref = {{cascite|correct|CAS}} | CASNo=122-34-9 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = SG0C34SMY3 | ChEMBL_Ref = {{ebicite|changed|EBI}} | ChEMBL = 1605837 | PubChem=5216 | KEGG_Ref = {{keggcite|correct|kegg}} | KEGG = C11172 | ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI = 27496 | SMILES = Clc1nc(nc(n1)NCC)NCC }} |Section2={{Chembox Properties | C=7 | H=12 | Cl=1 | N=5 | Appearance=White crystalline powder | Density=1.3 g/cm<sup>3</sup> | MeltingPtC=225-227 | BoilingPt= | Solubility=5 mg/L | SolubleOther = Soluble in methanol, chloroform, and diethyl ether; slightly soluble in pentane | Solvent=other solvents | VaporPressure =0.000810 mPa at 20&nbsp;°C | LogP = 1.9600 }} |Section3={{Chembox Hazards | MainHazards= | FlashPt= | AutoignitionPt = }} }}

'''Simazine''' is an herbicide of the triazine class. The compound is used to control broad-leaved weeds and annual grasses.

Simazine's HRAC classification is Group C1, Group C (global, Aus), Group 5 (numeric), as it inhibits photosynthesis at photosystem II.<ref>{{cite web |title=Classification of Herbicides According to Site of Action |url=https://www.weedscience.org/Documents/ShowDocuments.aspx?DocumentID=1193 |access-date=19 July 2025}}</ref>

==Preparation== Simazine may be prepared from cyanuric chloride and a concentrated solution of ethyl amine (at least 50&nbsp;percent by number) in water.<ref>{{cite web | url = https://pubchem.ncbi.nlm.nih.gov/compound/Simazine#section=Methods-of-Manufacturing&fullscreen=true | title = Simazine: Methods of Manufacturing | publisher = PubChem }}</ref> The reaction is highly exothermic and is therefore best carried out below 10&nbsp;°C.

Cyanuric chloride decomposes at high temperatures into hydrogen chloride 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, and was widely used as a residual non-selective herbicide, but is now banned in European Union states.<ref>{{CELEX|32004D0247|language=EN|format=PDF|text = 2004/247/EC: Commission Decision of 10 March 2004 concerning the non-inclusion of simazine in Annex I to Council Directive 91/414/EEC and the withdrawal of authorisations for plant protection products containing this active substance}}</ref> Like atrazine, a related triazine herbicide, it acts by inhibiting photosynthesis. It remains active in the soil for two to seven months or longer after application.

==See also== * Atrazine

==References== {{reflist}}

==External links== * [http://extoxnet.orst.edu/pips/simazine.htm Simazine], Extoxnet PIP

{{Herbicides}}

Category:Herbicides Category:Triazines Category:Chloroarenes Category:Group 5 herbicides