Purification Methods
Purify the thiol by dissolving ~45g in boiling H2O (100mL) (charcoal), filter and precipitate it by adding 50% aqueous NaOH (~80mL) to pH ~6. Dissolve the precipitate in EtOH, evaporate it to dryness, then crystallise it from boiling EtOH (~100mL, charcoal) to give yellow flat hexagonal plates (m 186o). It sublimes readily in vacuo. [King & Ware J Chem Soc 873 1939.] The picrate forms yellow needles from H2O with m 222o(dec). The 4-methylmercaptopyridine derivative crystallises from pet ether (m 47o , also 44-45o was reported, with a pK2 0 of 5.97) and was prepared by treatment with MeI/NaOH. Its picrate has m 2 4 5o (from H2O, MeOH or EtOH). The N-methyl-4-pyridinethiol derivative has m 168.5-170o (from EtOH), a pK2 0 of 1.30 and is soluble in CHCl3. [Albert & Barlin J Chem Soc 2384 1959, Beilstein 21 II 35, 22 III/IV 373, 22/7 V 147.]
