An example of green surfactant systems based on inherently biodegradable IL-derived amphiphilic oximes

Abstract

Abstract Progress in the development of biodegradable ionic liquids (ILs) leads to designing green surfactant formulations for miscellaneous applications. In this work, we present synthesis of a series of novel IL-derived amphiphilic pyridinium oximes composed by octylamide tail linked to the headgroup by means of amide, 4-((hydroxyimino)methyl)-1-(2-(octylamino)-2-oxoethyl)pyridin-1-iumbromide, 4-PyC8), alanyl ((S)-4-((hydroxyimino)methyl)-1-(2-((1-(octylamino)-1-oxopropan-2-yl)amino)-2-oxoethyl) pyridin-1-ium bromide, 4-PyAlaC8), or phenylalanyl ((S)-2-((hydroxyimino)methyl)-1-(2-((1-(octylamino)-1-oxo-3-phenylpropan-2-yl)amino)-2-oxoethyl)pyridin-1-ium bromide, 2-PyPheC8), S)-3-((hydroxyimino)methyl)-1-(2-((1-(octylamino)-1-oxo-3-phenylpropan-2-yl)amino)-2-oxoethyl)pyridin-1-iumbromide, 3-PyPheC8), and (S)-4-((hydroxyimino)methyl)-1-(2-((1-(octylamino)-1-oxo-3-phenylpropan-2yl)amino)-2-oxoethyl) pyridin-1-ium bromide, 4-PyPheC8) moiety. Their biodegradability examined in the closed bottle test shown the dependence on the amino acid structure and follows the tendency Phe > Ala > amide. Phenylalanine-based oximes demonstrate >30% of degradation in the CBT after 42 days and can be considered as inherently degradable. The acid ionization constant (pKa) of studied oximes determined by means of UV–vis spectroscopy at 27 °C were found to be in the range from 8.00 to 9.00. The pKa,app values of oximes in the presence of cationic gemini surfactants, 12-4-12- and 16-10-16, change insignificantly whereas they shifted upwards in the presence of anionic surfactant SDS. The nucleophilic cleavage of organophosphorus triester PNPDPP under optimal concentration conditions of 4-PyC8 come about with half-life times 40 s under mild condition (pH 9.00). These results provide new information on control the green microorganized nucleophilic systems for chemical decontamination.