2-Hydroxyethyl terephthalic acid is an organic compound with the formula HOC<sub>2</sub>H<sub>4</sub>O<sub>2</sub>CC<sub>6</sub>H<sub>4</sub>CO<sub>2</sub>H. It is the monoester of terephthalic acid and ethylene glycol. The compound is a precursor to poly(ethylene terephthalate) (PET), a polymer that is produced on a large scale industrially. 2-Hydroxyethyl terephthalic acid is a colorless solid that is soluble in water and polar organic solvents. Near neutral pH, 2-hydroxyethyl terephthalic acid converts to 2-hydroxyethyl terephthalate, HOC<sub>2</sub>H<sub>4</sub>O<sub>2</sub>CC<sub>6</sub>H<sub>4</sub>CO<sub>2</sub><sup>âÂÂ</sup>.
2-Hydroxyethyl terephthalic acid is an intermediate in both the formation and hydrolysis of PET. It is produced on a massive scale as the first intermediate in certain routes to PET. Specifically, it is produced in the course of the thermal condensation of terephthalic acid and ethylene glycol:
Further dehydration of 2-hydroxyethyl terephthalic acid gives PET.
It is also produced by the partial hydrolysis of PET, as catalyzed by the enzyme PETase. It is substrate for the enzyme MHETase.