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■ Structural and Ecotoxicological Profile of N-Alkoxymorpholinium-Based Ionic Liquids

Robert Salchner, Gerhard Laus, Simone Haslinger, Volker Kahlenberg, Klaus Wurst, Doris E. Braun, Stefan Vergeiner, Holger Kopacka, Herwig Schottenberger,* Alan Puckowski, Marta Markiewicz, Stefan Stolte, and Sven Nerdinger*

*Faculty of Chemistry and Pharmacy, Leopold-Franzens University, Innrain 80, 6020 Innsbruck, Austria

Abstract

Alkylation of N-methylmorpholine N-oxide (1, NMMO) using dialkyl sulfates gave N-alkyloxymorpholinium alkyl sulfates 2 and 3 (alkyl = Me, Et), which were subjected to ion metathesis. The tetrachloroferrates(III) 4 and 5 were found to be advantageous precursors for the chlorides 6 and 7 which were converted to six other salts. In summary, 13 new quaternary salts were prepared (IO4 8 and 9, BF4 10, N3 11, AcO 12, (MeO)2PO2 13, PF6 14, Tf2N 15) and one hydrate 7·H2O. Eleven X-ray crystal structures were determined. Nine salts had melting points below 100 °C, thus qualifying as ionic liquids (ILs), and three more below 110 °C. In addition, catalytic hydrogenation gave two protic ionic liquids (PILs), N-methylmorpholinium alkyl sulfates 16 and 17 (alkyl = Me, Et). This reductive degradation was also performed in aqueous solution. Ecotoxicological examinations of 3, 4, and 5 showed minor potential to interact with acetylcholinesterase (AChE), moderate acute toxicity towards rat leukemia IPC-81 cells, no adverse effect towards green algae Scenedesmus vacuolatus, but no ready biodegradability in sewage sludge.