1,3-Isobenzofurandione, 4,5,6,7-tetrahydro- (9CI) 2426-02-0 3,4,5,6-Tetrahydrophthalic acid anhydride 3,4,5,6-Tetrahydrophthalic anhydride EINECS 219-374-3 NSC 11211 NSC 61333