ɪɾ ɪz ˈɔːlsoʊ fˈɔːɹmd æz ɐ baɪpɹˈɑːdʌkt ɪn θˈæliəmpɹəmˈoʊɾᵻd ˌaɪədᵻnˈeɪʃən ʌv fˈɛnɑːlz wɪð θˈæliəm aɪ ˈæsɪtˌeɪt.
It is also formed as a by-product in thallium-promoted iodination of phenols with thallium(I) acetate.