Abstract
Glucaric acid has potential applications in food, pharmaceutical and polymer industries yet no methodology exists within the public domain for isolation of this key bio‐derived platform molecule as a pure, crystalline solid. Here we demonstrate the difficulties, which arise in doing so and report development of a process for derivation of free‐glucaric acid from its Ca2+/K+ glucarate salts, which are both commercially available. Employing Amberlyst‐15 (H+) exchange resin and azeotrope drying, powdered glucaric acid is prepared at > 99.96 % purity in 98.7 % dry yield.
Highlights
Feedstock homogeneity is a key concern within the chemical industry
HMBC NMR analysis of this syrup dissolved in D2O showed numerous 13C–1H interactions (Figure 2a). These correlate strongly with reference values for 2–4 bond H-C coupling in glucaric acid as well as its lactone and dilactone derivatives.[23]
As it had previously been proposed that freeze drying of this syrup yields glucaric acid, this was assessed through freezing in liquid N2 followed by evacuation at 50 °C, with HMBC analysis of the resulting thick orange syrup indicating that further lactonisation (ESI Figure S1) had occurred.[22]
Summary
Feedstock homogeneity is a key concern within the chemical industry. This is true for bio-derived product streams, which often lack the purity offered by refined-fossil fuel sources. As it had previously been proposed that freeze drying of this syrup yields glucaric acid, this was assessed through freezing in liquid N2 followed by evacuation at 50 °C, with HMBC analysis of the resulting thick orange syrup indicating that further lactonisation (ESI Figure S1) had occurred.[22] With an aim to decrease the temperature required for solvent removal, and thereby to minimise lactone formation, the solubility of K-glucarate in both polar protic and polar aprotic organic solvents was assessed (ESI Figure S2).
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