Maleic Anhydride (MA) is an organic compound with the chemical formula C₄H₂O₃. It is a colorless to white crystalline solid that is highly reactive and an important intermediate in the chemical industry. Maleic anhydride is primarily used in the production of unsaturated polyester resins, plasticizers, agrochemicals, and pharmaceuticals. It is derived from benzene, butane, or butene through an oxidation process.
The anhydride form of maleic acid (C₄H₄O₄), where the molecule is cyclic and contains a reactive carbonyl group (C=O), makes it highly reactive and valuable for various chemical processes. Maleic anhydride has applications in the polymer industry, automotive, building, and construction sectors due to its role in resins and composites.
Properties of Maleic Anhydride:
- Molecular Formula: C₄H₂O₃
- Molar Mass: 98.06 g/mol
- CAS Number: 108-31-6
- Functional Groups: Anhydride group (–C(=O)O–), derived from maleic acid.
- Reactivity:
- Maleic anhydride is highly reactive with water and alcohols, forming maleic acid and ester derivatives. It can also undergo nucleophilic addition reactions with amines and alcohols.
- It readily reacts with alkalies and bases, producing maleate salts.
- Maleic anhydride is a strong electrophile, participating in Michael addition and Diels-Alder reactions with dienes or nucleophilic species.
- It is also used as a precursor in the synthesis of pharmaceuticals, herbicides, and other specialty chemicals.
- Appearance: Colorless or white crystalline solid (can darken to brown or black on exposure to light and air).
- Odor: Has a sharp, pungent odor.
- Density: 1.48 g/cm³ at 20°C.
- Melting Point: 52–56°C (126–132°F).
- Boiling Point: 202°C (396°F).
- Solubility:
- Soluble in water, where it reacts to form maleic acid.
- Also soluble in many organic solvents, such as acetone, toluene, benzene, and ether.
- Vapor Pressure: 0.6 mmHg at 20°C.
- Reactivity with Water: Maleic anhydride reacts vigorously with water, hydrolyzing to maleic acid.
Uses of Maleic Anhydride:
- Polyester Resins: Used in the production of unsaturated polyester resins, widely used in fiberglass products.
- Chemical Synthesis: Used to make fumaric acid, malic acid, and other derivatives.
- Agriculture: Used in the manufacture of herbicides and insecticides.
- Plasticizers: Used in making plasticizers for PVC.