Studies of tetrazoles as rubber chemicals. I. Preparation and characterization of reactive antioxidants based on tetrazoles

摘要

AbstractThe novel reactive antioxidants based on tetrazoles that are stable at room temperature and convertible into the highly reactive nitrileimines by pyrolysis were prepared and the reactivity for carbon–carbon double bonds was evaluated. Antioxidants, i.e., 2‐substituted phenyl‐5‐(3′,5′‐di‐tert‐butyl‐4′‐hydroxyphenyl)tetrazoles (PHPT) were prepared with the reaction ofp‐toluenesulfonylhydrazone of 3,5‐di‐tert‐butyl‐4‐hydroxybenzaldehyde and substituted phenyl diazonium chloride in a mixed solvent of pyridine, ethanol, and water at −10°C to −20°C in 31‐61 yields. To evaluate the reactivities of PHPT for carbon–carbon double bonds,m‐chloro‐substituted PHPT was pyrolyzed in an excess of styrene at 160–170°C for 0.5 h to give the 1‐(3′‐chlorophenyl)‐3‐(3″,5″‐di‐tert‐butyl‐4″‐hydroxyphenyl)‐5‐phenyl‐2‐pyridazoline in a 44.1 yield by 1,3‐dipolar addition reaction of the nitrileimine formed from them‐chloro‐substituted PHPT. The thermogravimetric analysis of a mixture of proton isomer of PHPT and liquid polybutadiene