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 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 ...
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 in 1954 under the trade name of Diuron.
History
In 1952, chemists at
E. I. du Pont de Nemours and Company patented a series of
aryl
In organic chemistry, an aryl is any functional group or substituent derived from an aromaticity, aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar ...
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 ...
derivatives as
herbicides. 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
Hydrogen is the chemical element wi ...
, 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. It is an industrially significant commodity chemical, as well as a versatile starti ...
, which is treated with
phosgene 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-NH
2 + COCl
2 → Aryl-NCO
:Aryl-NCO + NH(CH
3)
2 → Aryl-NHCON(CH
3)
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, disallowing the electron flow from 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 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
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 ...
.
Toxicity
DCMU (Diuron) has been characterized as a known/likely human carcinogen based on animal testing.
References
{{Herbicides
Herbicides
Ureas
Toxicology
Anilines
Chlorobenzenes
Carcinogens