View source for DCMU

{{hatnote group|
{{Distinguish|text = the mercurial diuretic [[Diurone]]}}
{{for|the DC comics Movie Universe|DC Extended Universe}}
}}
{{chembox
|   ImageFile = Diuron.svg
|   ImageAlt = Skeletal formula of DCMU
|   ImageFile1 = DCMU-3D-balls.png
|   ImageAlt1 = Ball-and-stick model of the DCMU molecule
|   PIN = ''N''′-(3,4-Dichlorophenyl)-''N'',''N''-dimethylurea
|   OtherNames = 3-(3,4-Dichlorophenyl)-1,1-dimethylurea, Karmex, Diuron, Direx
| Section1 = {{Chembox Identifiers
|   ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 3008
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 116509
| SMILES = Clc1ccc(NC(=O)N(C)C)cc1Cl
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 278489
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C9H10Cl2N2O/c1-13(2)9(14)12-6-3-4-7(10)8(11)5-6/h3-5H,1-2H3,(H,12,14)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = XMTQQYYKAHVGBJ-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 330-54-1
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = C18428
| PubChem = 3120
| EC_number = 206-354-4
| RTECS = YS8925000
| UNNumber = 3077, 2767
| UNII = 9I3SDS92WY
  }}
| Section2 = {{Chembox Properties
|   C=9|H=10|Cl=2|N=2|O=1
|   Density = 1.48 g/cm<sup>3</sup>
|   MeltingPtC = 158
|   BoilingPtC = 180
|   Solubility = 42 mg/L
|   Appearance = white crystalline solid<ref name=PGCH/>
|   VaporPressure = 0.000000002 mmHg (20°C)<ref name=PGCH/>
  }}
| Section7 = {{Chembox Hazards
|   PEL = none<ref name=PGCH>{{PGCH|0247}}</ref>
|   IDLH = N.D.<ref name=PGCH/>
|   REL = TWA 10 mg/m<sup>3</sup><ref name=PGCH/>
|   FlashPt = noncombustible
|   FlashPt_ref =<ref name=PGCH/>
| GHSPictograms = {{GHS07}}{{GHS08}}{{GHS09}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|302|351|373|410}}
| PPhrases = {{P-phrases|201|202|260|264|270|273|281|301+312|308+313|314|330|391|405|501}}
  }}
}}

'''DCMU''' ('''3-(3,4-dichlorophenyl)-1,1-dimethylurea''') is an [[algicide]] and [[herbicide]] of the aryl [[ureas|urea]] class that inhibits [[photosynthesis]]. It was introduced by [[Bayer]] in 1954 under the trade name of '''Diuron'''.
==History==
In 1952, chemists at [[DuPont (1802–2017)|E. I. du Pont de Nemours and Company]] patented a series of [[aryl]] [[urea]] derivatives as [[herbicides]]. Several compounds covered by this patent were commercialized as herbicides: [[chlortoluron]] (3-chloro-4-methylphenyl) and DCMU, the (3,4-dichlorophenyl) example.<ref name=Todd>{{cite patent |country=US |number=2655445 |status=patent |gdate=1953-10-13 |fdate=1952-02-14 |pridate=1949-12-06 |invent1 =Todd C.W. |title=3-(Halophenyl)-1-methyl-1-(methyl or ethyl) ureas and herbicidal compositions and methods employing same |assign1=E. I. du Pont de Nemours & Co.}}</ref><ref name=Liu>{{cite book |doi=10.1016/B978-0-12-374367-1.00080-X |chapter=Phenylurea Herbicides |title=Hayes' Handbook of Pesticide Toxicology |year=2010 |last1=Liu |first1=Jing |pages=1725–1731 |isbn=9780123743671 }}</ref> Subsequently, over thirty related urea [[analogue (chemistry)|analogs]] with the same mechanism of action reached the market worldwide.<ref>{{cite web |url=http://www.alanwood.net/pesticides/class_herbicides.html#urea_herbicides |title=Urea herbicides |website=alanwood.net|access-date=2021-03-26}}</ref>
==Synthesis==
As described in the du Pont patent, the starting material is 3,4-dichloro[[aniline]], which is treated with [[phosgene]] to form a [[isocyanate]] derivative. This is subsequently reacted with [[dimethylamine]] to give the final product.<ref name=Todd />
:Aryl-NH<sub>2</sub> + COCl<sub>2</sub> → Aryl-NCO
:Aryl-NCO + NH(CH<sub>3</sub>)<sub>2</sub> → Aryl-NHCON(CH<sub>3</sub>)<sub>2</sub>

==Mechanism of action==
DCMU is a very specific and sensitive inhibitor of photosynthesis. It blocks the Q<sub>B</sub> [[plastoquinone]] binding site of [[photosystem II]], disallowing the electron flow from photosystem II to plastoquinone.<ref>{{Cite journal | doi = 10.1016/0014-5793(86)80911-5 | title = Evidence for a dual function of the herbicide-binding D1 protein in photosystem II | year = 1986 | last1 = Metz | first1 = J | last2 = Pakrasi | first2 = H | last3 = Seibert | first3 = M | last4 = Arntzer | first4 = C | journal = FEBS Letters | volume = 205 | issue = 2 | pages = 269| s2cid = 84205263 | doi-access = free }}</ref> This interrupts the photosynthetic [[electron transport chain]] in photosynthesis and thus reduces the ability of the plant to turn light energy into chemical energy ([[adenosine triphosphate|ATP]] and [[reductant|reductant potential]]).

DCMU only blocks electron flow from photosystem II, it has no effect on photosystem I or other reactions in photosynthesis, such as light absorption or carbon fixation in the [[Calvin cycle]].{{Citation needed|reason=reliable source needed for the whole sentence|date=April 2014}}

However, because it blocks electrons produced from water oxidation in [[PS II]] from entering the plastoquinone pool, "linear" photosynthesis is effectively shut down, as there are no available electrons to exit the photosynthetic electron flow cycle for reduction of [[NADP|NADP<sup>+</sup>]] to NADPH.
In fact, it was found that DCMU not only does not inhibit the [[Photophosphorylation#Cyclic photophosphorylation|cyclic photosynthetic pathway]], but, under certain circumstances, actually stimulates it.<ref>HUBER, S.C. EDWARDS, G.E. (1976), Studies on the Pathway of Cyclic Electron Flow in Mesophyll Chloroplasts of a C4 Plant, Biochimica et Biophysica Acta (BBA) - Bioenergetics, Volume 449, Issue 3, 6 December 1976, Pages 420-433, {{doi|10.1016/0005-2728(76)90153-5}}</ref><ref>{{cite journal | pmc =  1056483 | pmid=16665372 | volume=83 | issue=4 | title=Regulation of Cyclic Photophosphorylation during Ferredoxin-Mediated Electron Transport : Effect of DCMU and the NADPH/NADP Ratio |date=April 1987 | journal=Plant Physiol. | pages=965–9 | doi=10.1104/pp.83.4.965| last1=Hosler | first1=J. P. | last2=Yocum | first2=C. F. }}</ref>

Because of these effects, DCMU is often used to study energy flow in [[photosynthesis]].

==Toxicity==
DCMU (Diuron) has been characterized as a known/likely human carcinogen based on animal testing.<ref>{{cite web |title=Diuron |url=https://pubchem.ncbi.nlm.nih.gov/source/hsdb/382 |website=National Center for Biotechnology Information |publisher=United States National Library of Medicine |number=382 |access-date=9 November 2021}}</ref><ref>{{cite tech report |type=Memorandum |first1=Taylor |last1=Linda |first2=Rinde |last2=Esther |title=Carcinogenicity Peer Review of Diuron |number=20460 |institution=United States Environmental Protection Agency |date=1997-05-08 |url=https://www3.epa.gov/pesticides/chem_search/cleared_reviews/csr_PC-035505_8-May-97_042.pdf |format=PDF |place=Washington, D.C.}}</ref>

==References==
{{Reflist}}

{{Herbicides}}
{{phenylurea herbicides}}

[[Category:Herbicides]]
[[Category:Ureas]]
[[Category:Anilines]]
[[Category:Chlorobenzene derivatives]]
[[Category:Suspected carcinogens]]
[[Category:Group 5 herbicides]]