Due to time and material constraints, I'm interested in using sodium hydrosulfide hydrate (NaSH . X H2O) for a reaction involving organometallic complexes sensitive to the presence of water. Would it be appropriate to dissolve the reagent in dry solvent, over activated molecular sieves, to remove the water from the hydrate? I understand that the water incorporates itself into the crystal structure of the hydrate, and generally heating it would suffice, but the low melting point/potentially toxic nature of this reagent make me question dehydration by heating. Has anyone had any success with using activated sieves to dry hydrates in this manner?
Thanks,
Richard
Why not simply heat under high vacuum with an additional cryo trap? Anything that distills over can be killed with peroxide.
I have not used sieves for drying anything ionic. I have only used for solvents which water is immisible in. But I believe that they are less effective when water is expected to be strongly/hydrogen bonded.
Physical Data: mp (hydrate) 52–54 °C; anhyd, 350 °C; d 1.79 g cm−3; pKa (HS− ⇌ S2− + H+) 14.15. Solubility: v sol H2O; sol EtOH, DMF (colored solution). Form Supplied in: yellow chips (NaSH·xH2O, may be principally NaSH·2H2O); also available anhydrous; may contain Na2S, Na2S2O3 Na2CO3.
Analysis of Reagent Purity: iodometric titration.
Preparative Methods: saturation of ethanolic Sodium Hydroxide with Hydrogen Sulfide;5 anhydrous NaSH is obtained by precipitation with ether.!! -->This might be an option. Dissolve you crystals in EtOH than add Ether (e.g. DIPE, MTBE) until precipitation. Filter under inert conditions and dry over P2O5 in exsiccator.
KF-titration for water determination
Saturation with H2S shifts the equilibrium, 2NaSH ⇌ Na2S + H2S, to the left, as does operation in a solvent less polar than water or addition of NaHCO3 to Na2S. Handling, Storage, and Precautions: store in cool, dry place under nitrogen. Exposure to air forms Na2S2O4 and Na2CO3; very hygroscopic. Flammable; produces SO2 on combustion. Stench. A reducing agent. Incompatible with acids (produces H2S), with strong oxidizing agents, and with Zn, Al, and Cu. Corrosive (NaSH + H2O ⇌ NaOH + H2S). Use in a well‐ventilated fume hood. Toxicity like that of Na2S. Extremely destructive to mucous membranes, eyes, upper respiratory tract, and skin. Can cause blindness; inhalation can be fatal. Decontamination with FeCl3 (production of insoluble iron sulfides).
Dear Richard, in theory you can use sieves 3A for removing water from hydrates, since water bonds to the sieves stronger than in many hydrates, however there are a lot of variables there...if you want to try maybe dissolve it in ether and add stabilizer and sieves 3A. But i strongly recommend to do what Anthony suggested.
Hello Richard, how are you?
I'm working on determination of glyceraldehyde (GA) and dyhidroxyacetone (DHA) (main oxidation products of glycerol) and since we make the oxidations in aqueous media we tried the drying of aqueous solutions of these analytes with molecular sieves (we also add pyridine to the medium because the derivatization reaction is performed in pyridine). Anyway, when we saw the chromatograms we found new peaks. We strongly believe that those structures are hydrates (altought we haven't corroborated it by GC-MS or other techniques). In our opinion, those hydrates are only formed when the analytes are dissolved in water and the drying process seems not to affect this structure. That is our experience. Good luck!
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