The invention relates to selected derivatives of 1-oxyl-2,2,6,6-tetramethyl-4-hydroxy-piperidine and 1-oxyl-2,2,6,6-tetramethyl-4-aminopiperidine, which are effective as inhibitors to prevent the premature polymerization of acrylic and methacrylic acids, their esters, their amides, vinyl acetate and acrylonitrile in the presence of water.
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