A series of ionic liquids (ILs) have been synthesized, and the dissolution ability of chitin has been evaluated under mild conditions. We have focused on tris­(2-hydroxyethyl)­methylammonium (THEMA) type ILs. These [THEMA]-type ILs partly dissolved chitin, and addition of ethylenediamine (EDA) was confirmed to improve the chitin dissolution. Relatively high hydrogen bond accepting ability of the IL/EDA mixtures was required to dissolve chitin. Among these mixtures, the [THEMA]­[OAc]/EDA mixture dissolved chitin completely without heating. As other potential solvents, a series of tetraalkylammonium hydroxides/water mixtures was also found to dissolve chitin without heating. Conversion of chitin to chitosan during the dissolution process has been found in such tetraalkylammonium hydroxides/water mixtures in spite of the fact that almost no deacetylation was found in the IL/EDA mixture. The effect of ILs and onium hydroxides on both chitin dissolution and deacetylation ability was discussed.

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