prov:value
| - Other suitable substituents on the R1 to R4 groups include halides such as chloride, bromide and iodide, thiol, ???OH, A1-O???, ???S-A1, ???CO-A1, ???NH2, ???NHA1, ???NA1A2, ???CO???NA1A2, ???NO2, ???O, in which A1 and A2, independently, are non-aromatic groups preferably having from 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms, e.g. methyl, ethyl, propyl and isopropyl.
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