Processes for the preparation of 2,5-dihydroxybenzenesulfonic acid salts
Processes for the preparation of 2,5-dihydroxybenzenesulfonic acid salts of formula (I) and a crystalline form of potassium 2,5 2,5-dihydroxybenzenesulfonic acid are provided.
1. A crystalline form of potassium 2,5-dihydroxybenzenesulfonate having characteristic 2θ values of 8.8, 13.7, 15.6, 18.9, 21.4, 26.8, 27.7 and 30.3(±1).
2. The crystalline form of potassium 2,5-dihydroxybenzenesulfonate of claim 1 made by a process comprising the steps of
(i) sulfonation of hydroquinone of formula (II) using sulfuric acid to provide a compound of formula (III)
ii) treating the compound of formula (III) with potassium 2-ethylhexanoate; and
iii) precipitating the potassium 2,5-dihydroxybenzenesulfonate using ethyl acetate.
3. The crystalline form of potassium 2,5-dihydroxybenzenesulfonate of claim 2 , wherein the potassium 2,5-dihydroxybenzenesulfonate is achieved in a yield of at least 75%.
4. A crystalline form of potassium 2,5-dihydroxybenzenesulfonate having 2θ values of 8.8, 15.6, 17.7, 18.9, 21.4, 21.5, 26.8, 26.9, and 35.9(±1).
5. The crystalline form of potassium 2,5-dihydroxybenzenesulfonate of claim 4 crystallized from a water/solvent mixture.
6. The crystalline form of potassium 2,5-dihydroxybenzenesulfonate of claim 5 wherein the solvent is isopropyl alcohol.
7. The crystalline form of potassium 2,5-dihydroxybenzenesulfonate of claim 6 precipitated using ethyl acetate.
8. A crystalline form of potassium 2,5-dihydroxybenzenesulfonate having 2θ values of 15.6, 18.9, 21.3, 21.4, 27.7, and 30.3(±1).
9. The crystalline form of potassium 2,5-dihydroxybenzenesulfonate of claim 8 crystallized from a water/solvent mixture.
10. The crystalline form of potassium 2,5-dihydroxybenzenesulfonate of claim 9 wherein the solvent is acetone.
11. The crystalline form of potassium 2,5-dihydroxybenzenesulfonate of claim 10 precipitated using ethyl acetate.