Sodium monothiophosphate
Template:Chembox Sodium monothiophosphate, or sodium phosphorothioate, is an inorganic compound with the chemical formula Template:Chem2. It is a sodium salt of monothiophosphoric acid (Template:Chem2). Sodium monothiophosphate forms hydrates Template:Chem2. The anhydrous form and all hydrates are white solids. The anhydrous salt (x = 0) (Template:Chem2) decomposes without melting at 120-125 °C. More common is the dodecahydrate (Template:Chem2). A nonahydrate is also known (Template:Chem2).
Related salts are the sodium dithiophosphate undecahydrate Template:Chem2, sodium trithiophosphate undecahydrate Template:Chem2, and sodium tetrathiophosphate octahydrate Template:Chem2.[1]
Preparation
Sodium monothiophosphate is prepared by the base hydrolysis of thiophosphoryl chloride using aqueous sodium hydroxide:[2][3]
This reaction affords the dodecahydrate, which is easily dehydrated.
Partial dehydration over 6.5 M [[Sulfuric acid|Template:Chem2]] gives the nonahydrate. Under flowing [[Nitrogen|Template:Chem2]], the anhydrous salt is formed.[4]
Sodium monothiophosphate decomposes at neutral pH. Silicone grease catalyses the hydrolysis of the monothiophosphate ion Template:Chem2, so it is recommended that it is not used in the glass joints.[5]
In the anhydrous salt, the P-S bond is 211 pm and the three equivalent P-O bonds are short at 151 pm. These disparate values suggest that the P-S bond is single.[6]
References
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