Kinetics of 4-acetoxybenzoic acid synthesis

Abstract

High-temperature polymers have found a wide range of uses in recent decades. 4-Acetoxybenzoic acid (PABA) is used as a monomer for the polymerization of one such thermotropic polymer. Information on polycondensation of already prepared PABA is available in the literature. However, information in the literature concerning the kinetics of PABA synthesis by acetylation of 4-hydroxybenzoic acid (PHBA) using acetic anhydride is limited. The reaction between PHBA and acetic anhydride in a carrier solvent, Therminol-66 (T-66), was investigated. Aspects of the global reaction mechanism and the dependence of the reaction rate on acetic anhydride concentration were determined. Nuclear Magnetic Resonance (NMR) spectrometry and gravimetric analysis were used to analyze the samples collected from a 3 l batch reactor. The specific rate constant and the activation energy of the reaction were determined and a rate equation for the reaction suggested.

Keywords:

• 4-Acetoxybenzoic acid
• synthesis
• kinetics
• rate equation
• in situ synthesis
• high temperature polymer
• 4-hydroxybenzoic acid
• acetic anhydride.