Problems encountered in the synthesis of 3-amino-4-hydroxybenzoic acid

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Problems encountered in the synthesis of 3-amino-4-hydroxybenzoic acid: Are the two synthetic routes viable? The first step involves converting p-hydroxybenzoic acid to 3-nitro-4-hydroxybenzoic acid. The nitration reaction for introducing the nitro group proceeded smoothly, but strict control over the reaction conditions was necessary; the yield obtained was satisfactory and close to what was expected. The second step involves converting 3-nitro-4-hydroxybenzoic acid to 3-amino-4-hydroxybenzoic acid, by reducing the nitro group without affecting other functional groups. Reducing agents such as sodium dithionite and reduced iron powder yielded products with melting points in the range of 210–220°C, while hydrazine-based reducing agents gave products with a melting point of 230°C and also produced a significant amount of carbonized byproducts. For the first nitrosation step, the second step remains unchanged; the melting point of the reaction product is between 209 and 212. Which organic solvent is more suitable for the first step? In the second step, this post was last edited by zxh6267 on 2009-4-6 at 17:41.]