Synthesis of sulfated alginate from its tributylammonium salt: Comparing the sulfating agents H2SO4-DCC and SO3·py

Alexandra L Mutch; Vito Ferro; Anitha A; Lisbeth Grøndahl

doi:10.1016/j.carbpol.2023.121488

Synthesis of sulfated alginate from its tributylammonium salt: Comparing the sulfating agents H₂SO₄-DCC and SO₃·py

Carbohydr Polym. 2024 Jan 15:324:121488. doi: 10.1016/j.carbpol.2023.121488. Epub 2023 Oct 14.

Authors

Alexandra L Mutch¹, Vito Ferro¹, Anitha A², Lisbeth Grøndahl³

Affiliations

¹ School of Chemistry and Molecular Biosciences, The University of Queensland, Cooper Road, Brisbane, Queensland 4072, Australia.
² School of Chemistry and Molecular Biosciences, The University of Queensland, Cooper Road, Brisbane, Queensland 4072, Australia. Electronic address: a.sudheeshkumar@uq.edu.au.
³ School of Chemistry and Molecular Biosciences, The University of Queensland, Cooper Road, Brisbane, Queensland 4072, Australia. Electronic address: l.grondahl@uq.edu.au.

PMID: 37985083
DOI: 10.1016/j.carbpol.2023.121488

Abstract

Direct comparison of the sulfating agents H₂SO₄-DCC and SO₃·py for the synthesis of sulfated alginate (S-Alg) as well as detailed characterisation of the products that form is lacking. This study involving three researchers used the tributylammonium salt of alginate (T-Alg) as a common substrate for the sulfation reactions. It was found that the use of H₂SO₄-DCC resulted in poor control of the degree of sulfation (DS) and that the S-Alg polymers contained nitrogen (determined by elemental analysis) as a result of formation of an unwanted N-acylurea adduct. Additionally, a large reduction in chain length was confirmed. In contrast, the use of SO₃·py gave reasonable control over DS, resulted in high yields, showed no contamination and no clear change in chain length. Detailed characterisation of such S-Alg polymers by ¹H NMR, ¹³C NMR and ¹H,¹³C-HSQC NMR confirmed sulfation at C2 and C3 with a preference for C2.

Keywords: Alginate sulfate; Fabrication; Infrared spectroscopy; Nuclear magnetic resonance spectroscopy.