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Solubility and esterification kinetics of terephthalic acid in ethylene glycol III. The effects of functional groups
Author(s) -
Yang K. S.,
An K. H.,
Choi C. N.,
Jin S. R.,
Kim C. Y.
Publication year - 1996
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19960516)60:7<1033::aid-app14>3.0.co;2-1
Subject(s) - terephthalic acid , ethylene glycol , chemistry , ethylene , polymer chemistry , hydrogen bond , benzoic acid , prepolymer , intramolecular force , organic chemistry , catalysis , nuclear chemistry , molecule , polyester , polyurethane
Clear time ( t cl ), the time required for the turbid mixture of terephthalic acid (TPA) and ethylene glycol (EG) to be clear, was measured to examine the effect of poly(ethylene terephthalate) (PET) prepolymer (DP of 1–5) on the kinetics of dissolution and/or ester‐ification of TPA with EG. The t cl of the mixture of TPA/EG (1 : 1.5 in molar ratio) was reduced to 1 : 2.2 or 1 : 3.5 by addition of 30 wt % of PET prepolymer or bis‐(2‐hydroxyl ethyl) terephthalate (BHET), respectively. Diethyl terephthalate (DET) as an addititive was used as a model compound to examine the effects of the —OH group on the esterification reaction of TPA/EG. The t cl value increased with addition of DET. The effect of the carbonyl group was also examined by determining esterification rates of benzoic acid (BA) with either ethylene glycol monobezoate (EGMB) as a compound with carbonyl group, or 2‐penoxyethanol (2‐PhE) as a compound without the carbonyl group. The reaction rate of BA with EGMB was much higher than that of BA with 2‐PhE, which indicates that the carbonyl group gave an increasing effect of the esterification rate. Fourier transform infrared spectra showed that the —OH group in both BHET and EGMB formed intramolecular hydrogen bonding with the ester carbonyl group. On the basis of these observations, we concluded that the electron density of oxygen in the hydroxyl group increased through the formation of the intramolecular hydrogen bond. The increased electron density gave the —OH group easier access to the carbonyl carbon in BA, leading to an increase in the esterification rate. © 1996 John Wiley & Sons, Inc.