Abstract
It was reported that every mono-alkali metal hydroxybenzoate turned into the corresponding di-alkali benzoate accroding to Eq. ( 1 ) at 360°C, except monopotassium salicylate. However, it has now been clarified by the microthermal and UV analyses that disodium phydroxybenzoate (P0B-Na2) formed from Eq. ( 1 ) rearranges into salicylic acid (SA) and 4- hydroxyisophthalic acid (4-OIP) at above 300°C in CO, atmosphere and at still higher temperature in N2. The DTA curve of this rearrangement consists of three peaks. Two endothermic peaks are attributed to the formation of 4-01P and the evolution of gases from the thermal decomposi- tion of POB-Na2, and one exothermic peak is due to the formation of SA. The formation of 4-OIP is accelerated with heating and the increase in CO, pressure. The reaction of Eq. ( 2 ) occurs in N, atmospheres, while the reaction of Eq. ( 3 ) takes place under CO, . The reaction of 4-0IP-Na3 with phenol and sodium phenolate also takes place at elevated pressures.
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