dimetüütereftalaat

Dimetüütereftalaat is the dimethyl ester of terephthalic acid. It is a white crystalline solid with the chemical formula C10H10O4. Dimethyl terephthalate is primarily used as a raw material in the production of polyethylene terephthalate (PET) polymers, which are widely used in the manufacturing of plastic bottles, polyester fibers, and films.

The synthesis of dimethyl terephthalate typically involves the esterification of terephthalic acid with methanol. This reaction can be catalyzed by an acid, such as sulfuric acid. The process yields dimethyl terephthalate and water. Alternatively, it can be produced by the oxidation of p-xylene followed by esterification.

Dimethyl terephthalate is a solid at room temperature and has a melting point of around 140-142 degrees Celsius. It is sparingly soluble in water but soluble in organic solvents like ethanol and diethyl ether. Its stability under normal conditions makes it suitable for storage and transportation.

In the production of PET, dimethyl terephthalate undergoes a transesterification reaction with ethylene glycol, often at elevated temperatures and in the presence of a catalyst. This process releases methanol as a byproduct and forms bis(2-hydroxyethyl) terephthalate, which then polymerizes to PET. While direct esterification of terephthalic acid with ethylene glycol is also a common route for PET production, the use of dimethyl terephthalate offers certain advantages in process control and purity.