Question

How is Dacron obtained from ethylene glycol and terephthalic acid?

Answer 1

Hint: Dacron is the other name of Terylene. Terylene (Dacron) is a polymer (polyester), made by using ethylene glycol and terephthalic acid. The polymerization between these two is condensation polymerization.

Complete step by step answer:
Dacron is a polyester made from two different monomers, terephthalic acid and ethylene glycol. The monomers in a polyester are linked together by ester linkages ${\text{RCOO}}{{\text{R}}^{\text{'}}}$. The two monomers combine to form polyethylene terephthalate units (PET). It is made by condensation polymerization where one molecule of water is lost when ethylene glycol and terephthalic acid are joined together. But many synthetic polymers like polyethylene are made by addition polymerization where there is no loss of any small molecules.
The preparation of Dacron can be known from the following mechanism of its synthesis. Dacron is a polyester and a polyester is prepared from reaction between an acid and an alcohol. The acid here is benzene-1,4-dicarboxylic acid and the alcohol is ethane-1,2-diol. When these monomer molecules approach each other, they combine to form a new compound, a polymer known as Dacron. But the polymer linkages between the two monomer units occur by the loss of a water molecule. The -OH group from terephthalic acid and –H from ethylene glycol combine to form a water molecule and gets lost from the polymer in each and every linkage. This type of polymerization is known as condensation polymerization. The polymer consists of ester ${\text{ - COOR}}$ linkages and the ester is suffixed as ate. So the name of Dacron is polyethylene terephthalate (PET).

Note: Dacron is sometimes also known as Terylene and is a synthetic polymer called polyester. It is used in the textile industry as a fabric, in plastic industry as a strong thermosetting plastic to make plastic articles, bottles etc. and also is used as a resin.