Maleic anhydride (CAS Number: 108-31-6) is the anhydride form of maleic acid. The anhydride compound is used as an intermediate product in the chemical industry, particularly in the production of plasticizers, unsaturated polyester resins, and raw materials for paints and coatings.
Other applications of maleic anhydride include the synthesis of pesticides, colorants, medications, tanning agents and curing agents for epoxy resins.
What makes this corrosive chemical so interesting is its ability to transition from the solid to the gaseous phase even at room temperature.
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Structure of maleic anhydride
Maleic anhydride (CAS Number: 108-31-6) is produced by partial oxidation of n-butane. Along with isomers of butene, n-butane can be found in a C4 fraction obtained through steam cracking.
Some older methods use benzene instead of n-butane to synthesize the anhydride form of maleic acid (also known as cis-butenedioic acid). However, this is not always economical because benzene prices are constantly rising.
The modern catalytic process produces maleic anhydride by attaching oxygen to and removing water from a 4-carbon molecule without affecting the 4 carbon atoms. As a result, the new method is considered especially material efficient.
Properties of maleic anhydride
Maleic anhydride (CAS Number: 108-3-6) is also known as furan-2,5-dione and dihydro-2,5-dioxofuran. The organic compound is a white solid and can appear as a crystalline powder, lumps or needles. It also has a characteristic acrid odor.
Maleic anhydride can dissolve in water and many other solvents to form maleic acid. As is very common with unsaturated compounds, maleic anhydride easily undergoes addition reactions at its double bonds.
Maleic anhydride is a reactive dienophile that is commonly used as a substrate in Diels-Alder reactions, which is why it is found as a raw material in the manufacture of pesticides and pharmaceuticals.
The chemical is able to transition from the solid to the gaseous phase at room temperature, but it can be shipped and sold in the molten state at temperatures above 70 degrees Celsius. However, it is of crucial importance to be cautious when handling maleic anhydride because the compound can become a toxic air contaminant at as low as 20 degrees Celsius, causing irritation of the skin, mucous membranes, airways and eyes.
As an industrial intermediate product, it is widely used in the manufacture of unsaturated polyesters and in the synthesis of tensides, insecticides, herbicides, fungicides, growth regulators (e.g. maleic anhydride), as well as in other chemical compounds, such as 1,4-butanediol, which is used in the production of polyurethane and elastanes, or co-polymers, which are an important lubricant.