Vj. Koshy et al., INVESTIGATIONS ON INTERMEDIATE ACETAL FORMATION DURING POLAROGRAPHIC ESTIMATION OF CERTAIN BENZALDEHYDE DERIVATIVES, Analytica chimica acta, 307(1), 1995, pp. 55-60
Terephthalaldehydic acid methyl ester (TAE) and 4-carboxybenzaldehyde
(CBA) which are identified as critical impurities in the manufacturing
of dimethyl terephthalate (DMT) and purified terephthalic acid (PTA),
respectively, are compounds under investigation. During their polarog
raphic estimation, it is seen that TAE had good stability in alkaline
water-methanol whereas CBA was converted to an electroinactive species
. Nuclear magnetic resonance, infrared, ultraviolet and mass spectrome
tric techniques were employed to identify the electroinactive product
as an acetal. Neutralization of the acidic group in CBA is seen to pre
vent acetal formation. A method has been developed for the quantificat
ion of TAE and CBA incorporating a preconcentration step, and applied
to their analysis in DMT and PTA.