The present invention relates to a compound represented by the following general formula (I): wherein R 1 and R 2 independently represent a monovalent hydrocarbon group; R 3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; X represents a divalent hydrocarbon group; and R 4 , R 5 and R 6 independently represent a monovalent organic group or a group represented by the following general formula (II): in which R 7 and R 8 independently represent a monovalent hydrocarbon group; and R 9 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, with the proviso that R 5 and R 6 may combine together to form a divalent hydrocarbon group. The aforementioned compounds are useful as a polymerization inhibitor and the like.