Abstract
A series of linear all-ortho alkylphenol-formaldehyde novolak resins were prepared by reaction of bromomagnesium alkylphenoxide with paraformaldehyde in benzene. The alkylphenols were p-nonylphenol, p-amylphenol, p-tert-octylphenol, p-tert-butylphenol, m-tert-butylphenol, p-sec-butylphenol, p-ethylphenol, m-ethylphenol, 3, 4-xylenol, 3, 5-xylenol, p-cresol, m-cresol, p-methoxyphenol, m-methoxyphenol, and phenol. The antioxidant effects of these oligomers on the autoxidation of lard were examined by oven tests at 60°C. The oligomers of phenols linked with all ortho methylene-bridges showed good antioxidant effects comparable to those of BHT. Both the substituents on the aromatic rings and molecular weights of the oligomers determined the strength of these effects. Phenolic oligomers having methoxyl groups at the para positions showed excellent antioxidant effects. The most effective molecular weights for these oligomers ranged from about 6001, 000. The antioxidant effects of oligomeric phenolic compounds appeared to arise from cooperative intra-molecular OH-OH hydrogen bonding from adjacent aromatic hydroxyl groups along the chain.
