1979 Volume 36 Issue 5 Pages 311-315
Bis (2-hydroxyethyl) terephthalate is an important intermediate in the industrial poly (ethylene terephthalate) production. The reaction of terephthalic acid with ethylene oxide to form bis (2-hydroxyethyl) terephthalate was studied in the presence of Group V compounds (R3X; R=alkyl, phenyl, X=P, As, Sb) in organic solvents in order to clarify the catalytic action of these compounds. On the bases of the isolation of the intermediate and kinetic data, it was proved that the actual catalyst for the esterification was not R3X itself when X was phosphine or arsine but its quaternary salt of terephthalic acid (HO2C-C6H4-CO2 (-) X⊕ (R3) C2H4OH) formed from terephthalic acid, ethylene oxide, and R3X (X=P, As). On the other hand, when triphenylstibine was used as catalyst, quaternary stibonium terephthalate was not formed and hence the esterification reaction did not proceed. The rate of esterification of terephthalic acid with ethylene oxide decreased in the following order;
(n-C4H9) 3P> (C6H5) 3P>> (C6H5) 3As>> (n-C4H9) 3Sb, (C6H5) 3Sb.
