Patent ID: 6902663

Claim:
A method for inhibiting the premature polymerization of ethylenically unsaturated monomers comprising adding to said monomers A) an effective amount of at least one inhibitor selected from the group consisting of C-nitrosoaniline compounds; and B) an effective amount of oxygen or air to enhance the inhibiting activity of said inhibitors; wherein the inhibitor is selected from the group consisting of C-nitrosoaniline compounds of the structure: wherein: R 1 and R 2 are independently selected from the group consisting of hydrogen, alkyl, aryl, acyl, hydroxyl, alkoxy, nitroso, and sulfonyl, or R 1 and R 2 can form a cyclic ring that is aryl, cycloalkyl, polyaryl, or heterocyclic; R 3 through R 7 are independently selected from the group consisting of hydrogen, alkyl, aryl, acyl, hydroxyl, alkoxy, acyloxy, NR 8 (R 9 ), nitro, nitroso, halogen, and sulfonyl, or any two adjacent R's can form a cyclic ring that is aryl, cycloalkyl, polyaryl, or heterocyclic, provided that at least one of R 3 through R 7 must be a nitroso group; and R 8 and R 9 are independently selected from the group consisting of hydrogen, alkyl, aryl, acyl, and nitroso.