DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) is an

algicide Algaecide or algicide is a biocide used for killing and preventing the growth of algae, often defined in a loose sense that, beyond the biological definition, also includes cyanobacteria ("blue-green algae"). An algaecide may be used for controlled ...

and

herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

of the aryl

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important r ...

class that inhibits

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

. It was introduced by

Bayer Bayer AG (, commonly pronounced ; ) is a German multinational corporation, multinational pharmaceutical and biotechnology company and one of the largest pharmaceutical companies in the world. Headquartered in Leverkusen, Bayer's areas of busi ...

in 1954 under the trade name of Diuron.

History

In 1952, chemists at

E. I. du Pont de Nemours and Company DuPont de Nemours, Inc., commonly shortened to DuPont, is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours. The company played a major role in ...

patented a series of

aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used as ...

derivatives as

herbicides Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

. Several compounds covered by this patent were commercialized as herbicides: monuron (4-chlorophenyl),

chlortoluron Chlortoluron or chlorotoluron are the common names for an organic compound of the phenylurea class of herbicides used to control broadleaf and annual grass weeds in cereal crops. History In 1952, chemists at E. I. du Pont de Nemours and Company ...

(3-chloro-4-methylphenyl) and DCMU, the (3,4-dichlorophenyl) example. Subsequently, over thirty related urea analogs with the same mechanism of action reached the market worldwide.

Synthesis

As described in the du Pont patent, the starting material is a substituted aryl

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...

, an

aniline Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine In organic chemistry, an aromatic amine is an organic compound consisting of an aroma ...

, which is treated with

phosgene Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, espe ...

to form its

isocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...

derivative. This is subsequently reacted with

dimethylamine Dimethylamine is an organic compound with the formula (CH3)2NH. This secondary amine is a colorless, flammable gas with an ammonia-like odor. Dimethylamine is commonly encountered commercially as a solution in water at concentrations up to aroun ...

to give the final product. :Aryl-NH₂ + COCl₂ → Aryl-NCO :Aryl-NCO + NH(CH₃)₂ → Aryl-NHCON(CH₃)₂

Mechanism of action

DCMU is a very specific and sensitive inhibitor of photosynthesis. It blocks the Q_B

plastoquinone Plastoquinone (PQ) is an isoprenoid quinone molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis. The most common form of plastoquinone, known as PQ-A or PQ-9, is a 2,3-dimethyl-1,4-benzoquinone m ...

binding site of

photosystem II Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants, algae, and cyanobacteria. Within the photosystem ...

, disallowing the electron flow from photosystem II to plastoquinone. This interrupts the photosynthetic

electron transport chain An electron transport chain (ETC) is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples th ...

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 The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into ...

. However, because it blocks electrons produced from water oxidation in

PS II Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants, algae, and cyanobacteria. Within the photosyst ...

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⁺ to NADPH. In fact, 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

Toxicity

DCMU (Diuron) has been characterized as a known/likely human carcinogen based on animal testing.

References

{{Herbicides Herbicides Ureas Toxicology Anilines Chlorobenzenes Carcinogens