Dimethyl phthalate (DMP) is an organic compound and phthalate ester. it is a colourless and oily liquid that is soluble in organic solvents, but which is only poorly soluble in water (~4 g/L). It is used in a variety of products and is most commonly used as insect repellent such as ectoparasiticide for mosquitoes and flies for animal livestock. The short-chain or low molecular weight phthalate is also frequently used in consumer products such as cosmetics, ink, soap, household cleaning supplies, etc. Other uses of DMP include solid rocket propellants and plastics. The U.S Environmental Protection Agency has classified Dimethyl phthalate as not classifiable for human carcinogenicity. Its oral LD50 is 4390 to 8200 mg/kg bw/d in rats and the dermal LD50 is 38000 mg/kg bw in rats and more than 4800 mg/kg bw in guinea pigs. Synthesis Dimethyl phthalate is manufactured commercially via the esterification of phthalic anhydride with methanol. The reaction can be catalysed by a strong acid, such as sulfuric acid; various lewis acids may be used as an alterative, including complexes of titanium, zirconium or tin. Excess methanol is used to ensure complete conversion, with the remainder removed by distillation at the end. Applications Unlike most other phthalate esters, dimethyl phthalate is rarely used as a plasticizer for PVC. It is considered too volatile and causes excessive fuming during PVC processing. It is a good plasticizer for cellulose-esters, including cellulose acetate, cellulose acetate butyrate and cellulose propionate compositions. Historically, this led to it being present in nail polish and some artificial nails but it is not commonly used today. It is used as a plasticizer for cellulose acetate phthalate, which is used to make enteric coatings for medicines. Other cosmetic uses include as a fixative for perfumes, although it is not as commonly used as DEP. Dimethyl phthalate is able to dissolve nitrocellulose which made it historically important in some automotive coatings and vanishes. Insect repellent DMP can be used as an insect repellent and is especially useful against ixodid ticks responsible for Lyme disease. DMP has been shown to deter species of mosquitoes such as Anopheles stephensi, Culex pipeins and Ades aegypti. Metabolism/Biotransformation DMP administered orally in rats largely undergoes phase I biotransformation to monomethyl phthalate (MMP) via hydrolysis in the liver and intestinal mucosa. MMP may also be further hydrolysed to phthalic acid. However, low molecular weight phthalates such as MMP are primarily excreted