Diethyl phthalate (DEP) is a phthalate

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ...

. It occurs as a colourless liquid without significant odour but has a bitter, disagreeable taste. It is more dense than water and insoluble in water; hence, it sinks in water.

Synthesis and applications

Diethyl phthalate is produced by the reaction of

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

with phthalic anhydride, in the presence of a strong acid

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

It finds some use as a specialist plasticiser in PVC, it has also been used as a blender and fixative in

perfume Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent ...

Biodegradation

Biodegradation by microorganisms

Biodegradation Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegra ...

of DEP in soil occurs by sequential

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysi ...

of the two diethyl chains of the phthalate to produce monoethyl phthalate, followed by phthalic acid. This reaction occurs very slowly in an abiotic environment. Thus there exists an alternative pathway of biodegradation which includes transesterification or demethylation by microorganisms, if the soil is also contaminated with

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is ...

, that would produce another three intermediate compounds, ethyl methyl phthalate, dimethyl phthalate and monomethyl phthalate. This biodegradation has been observed in several soil

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

. Some bacteria with these abilities have specific enzymes involved in the degradation of phthalic acid esters such as phthalate oxygenase, phthalate dioxygenase, phthalate dehydrogenase and phthalate decarboxylase. The developed intermediates of the transesterification or demethylation, ethyl methyl phthalate and dimethyl phthalate, enhance the toxic effect and are able to disrupt the membrane of microorganisms.

Biodegradation by mammals

Recent studies show that DEP, a phthalic acid ester (PAE), is enzymatically hydrolyzed to its monoesters by pancreatic cholesterol esterase (CEase) in pigs and cows. These

mammalian Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fu ...

pancreatic CEases have been found to be nonspecific for degradation in relation to the diversity of the alkyl side chains of PAEs.

Toxicity

Little is known about the chronic toxicity of diethyl phthalate, but existing information suggests only a low toxic potential. Studies suggest that some phthalates affect male reproductive development via inhibition of androgen biosynthesis. In rats, for instance, repeated administration of DEP results in loss of

germ cell Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embr ...

populations in the testis. However, diethyl phthalate does not alter sexual differentiation in male rats. Dose response experiments in fiddler crabs have shown that seven-day exposure to diethyl phthalate at 50 mg/L significantly inhibited the activity of chitobiase in the epidermis and hepatopancreas. Chitobiase plays an important role in degradation of the old

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton ( endoskeleton) in for example, a human. In usage, some of the ...

during the pre- moult phase.

Teratogenicity

When pregnant rats were treated with diethyl phthalate, it became evident that certain doses caused skeletal malformations, whereas the untreated control group showed no resorptions. The amount of skeletal malformations was highest at highest dose. In a following study it was found that both phthalate diesters and their metabolic products were present in each of these compartments, suggesting that the toxicity in embryos and fetuses could be the result of a direct effect.

Future investigation

Some data suggest that exposure to multiple phthalates at low doses significantly increases the risk in a dose additive manner. Therefore, the risk from a mixture of phthalates or phthalates and other anti-androgens, may not be accurately assessed studying one chemical at a time. The same may be said about risks from several exposure routes together. Humans are exposed to phthalates by multiple exposure routes (predominantly dermal), while toxicological testing is done via oral exposure.

References

{{DEFAULTSORT:Diethyl Phthalate Ethyl esters Phthalate esters Endocrine disruptors