I have an oxidized alginate which I want to sulfonate. The reaction bath is chlorosulfonic acid dissolved in formamide. Will the aldehyde in oxidized alginate react to chlorosulfonic acid, or will it react first to formamide via reductive amination, and then the amine will be sulfated (forming 2° amine)?
Chlorosulfonic acid is an acid chlorid. The typical reactons of acid chloride are reactions with Hydroxylgroups with the eleminiation of HCl to for a sulfonic-ester or with amides to form a sulfonamide.
With your reactions you will first get the formation of the sulfonamide. Which a a strong acid. The aldedhyd can now react with the hydroxy-groups of the alginate to from an acteal or a semiacteal. Or depending on the ratio of sulfonice acid - formaide an imin could be formed.
The reactions of the amine with an aldehyd ist not an redox-reaction it is an condensation reaction.
I have a few questions. What form is oxidized alginate in? What proportion of the functional groups in oxidized alginate are aldehyde groups? If formamide is a reagent, why don't we use pure chlorosulfonic acid or pure sufonamide? It's just out of curiosity.
Dear Jopeth Ramis many thanks for your interesting technical question. I think you did everything right. According to the useful link cited below the combination of chlorosulfonic acid and DMF is a good reagent for preparing sulfated alginate derivatives. Please have a look at
Synthesis and Anticoagulant activity of Sulfated alginate
https://rtt.kku.ac.th/ejournal/pa_upload_pdf/488427.pdf
(see attached pdf file)
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