Diuron

DCMU

Names
Other names 3-(3,4-Dichlorophenyl)-1,1-dimethylurea, Karmex, Diuron, Direx
Identifiers
CAS Number	330-54-1 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:116509 Y
ChemSpider	3008 Y
ECHA InfoCard	100.005.778
KEGG	C18428 Y
InChI InChI=1S/C9H10Cl2N2O/c1-13(2)9(14)12-6-3-4-7(10)8(11)5-6/h3-5H,1-2H3,(H,12,14) Y Key: XMTQQYYKAHVGBJ-UHFFFAOYSA-N Y InChI=1/C9H10Cl2N2O/c1-13(2)9(14)12-6-3-4-7(10)8(11)5-6/h3-5H,1-2H3,(H,12,14) Key: XMTQQYYKAHVGBJ-UHFFFAOYAZ
SMILES Clc1ccc(NC(=O)N(C)C)cc1Cl
Properties
Chemical formula	C9H10Cl2N2O
Molar mass	233.09 g·mol−1
Appearance	white crystalline solid
Density	1.48 g/cm3
Melting point	158 °C (316 °F; 431 K)
Boiling point	180 °C (356 °F; 453 K)
Solubility in water	42 mg/L
Vapor pressure	0.000000002 mmHg (20°C)
Hazards
EU classification (DSD)	Harmful (Xn); Dangerous for the environment (N)
Flash point	noncombustible
US health exposure limits (NIOSH):
PEL (Permissible)	none
REL (Recommended)	TWA 10 mg/m3
IDLH (Immediate danger)	N.D.
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) is an algicide and herbicide of the phenylurea class that inhibits photosynthesis. It was introduced by Bayer in 1954 under the trade name of Diuron.

DCMU is a very specific and sensitive inhibitor of photosynthesis. It blocks the plastoquinone binding site of photosystem II, disallowing the electron flow from where it is generated, in photosystem II, to plastoquinone. This interrupts the photosynthetic electron transport chain in photosynthesis and thus reduces the ability of the plant to turn light energy into chemical energy (ATP and 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.

However, because it absorbs electrons oxidized from water in PS II, the electron "hole" of PS I cannot be satisfied, effectively shutting down "linear" photosynthesis by blocking the reduction of NADP⁺ to NADPH. At the same time, it was found that DCMU not only does not inhibit the cyclic photosynthetic pathway, but, under certain circumstances, actually stimulates it.

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