a process for producing tert - amylphenols is described , comprising reacting isoamylene with phenols in the presence of an inorganic solid acid catalyst or an acidic ion exchange resin catalyst . this process permits efficient production of tert - amylphenols , i . e ., 2 , 4 - di - tert - amylphenol and p - tert - amylphenol . these tert - amylphenols are useful as starting materials for preparation of color formers for color photography , additives for resins , oil - soluble dyes , additives for lubricating oils , etc .