Silver hydroxide

Structural formula
General
Surname	Silver hydroxide
other names	Silver (I) hydroxide
Molecular formula	AgOH
External identifiers / databases
CAS number 12258-15-0 PubChem 10129950 ChemSpider 8305469 Wikidata Q9291459
properties
Molar mass	124.88 g mol −1
Physical state	firmly
pK s value	3.96 (25 ° C)
solubility	poorly soluble in water and methanol
safety instructions
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Silver hydroxide (silver (I) hydroxide), chemical formula AgOH , is a base as the hydroxide of silver . The unstable, brownish and poorly soluble solid can, for. B. electrolytically or from neutral aqueous silver nitrate solution with equimolar addition of the base NaOH . Silver hydroxide is in equilibrium with the also poorly soluble, more stable silver (I) oxide Ag ₂ O, with water being split off .

${\displaystyle \mathrm {2\ Ag^{+}+2\ OH^{-}\longrightarrow 2\ AgOH\downarrow } }$ ${\displaystyle \mathrm {\rightleftharpoons \ Ag_{2}O\downarrow +H_{2}O} }$

For the equilibrium reaction of silver hydroxide to silver oxide, the equilibrium constant K is 1.33 · 10 ⁻³ , with significantly less Ag ₂ O than AgOH in the solution at equilibrium .

${\displaystyle \mathrm {2\ AgOH\rightleftharpoons Ag_{2}O+H_{2}O\ (pKs=2{,}875)} }$

presentation

• Silver nitrate is dissolved in water. This silver nitrate solution is stirred into a sodium hydroxide solution while stirring . The resulting silver hydroxide precipitate is filtered off with suction, washed with water and then with methanol.

• Silver hydroxide can be precipitated from anhydrous alcoholic solution without the formation of silver oxide.

Reactions

A suspension of silver (I) oxide in water has a clearly alkaline reaction, since the reverse of the above reaction from silver oxide forms the base silver hydroxide.

The precipitation of AgOH from aqueous solution begins at pH 8.3 and is completed at pH 11.3. As an amphoteric hydroxide, AgOH goes back into solution at even higher pH values; in excess of a strongly alkaline solution of silver hydroxide, the soluble silver hydroxide anion [Ag (OH) ₂ ] ^{- is formed} :

${\displaystyle \mathrm {AgOH+OH^{-}\longrightarrow [Ag(OH)_{2}]^{-}} }$

By adding concentrated ammonia solution, the water-soluble diammine silver (I) complex [Ag (NH ₃ ) ₂ ] ⁺ is formed from silver hydroxide .

${\displaystyle \mathrm {AgOH+2\ NH_{3}\longrightarrow [Ag(NH_{3})_{2}]^{+}+OH^{-}} }$

Use in preparative chemistry

• The corresponding hydroxides can be prepared from the water-soluble halides chloride , bromide and iodide in a methanolic solution with a silver oxide suspension conveniently and without side reactions.
• The substitution of a chlorine or iodine ligand (–Cl or –I) by a hydroxyl group (–OH) is possible in some organic compounds by reacting with AgOH (Examples: The reaction of chlorosuccinic acid with silver hydroxide leads to malic acid with the formation of AgCl; the conversion of iodoethane to ethanol ).
• Quaternary ammonium halides can be converted into the corresponding, halide-free quaternary ammonium hydroxides with AgOH.
• Historical possibility for the representation of colloidal silver : In an alkaline solution of the sodium salt of protalbic or lysalbinic acid, hydrazine hydrate reduces AgOH to colloidal silver, which is very resistant.
• Tartronic acid (hydroxymalonic acid) is produced by the hydrolysis of monobromalonic acid with silver hydroxide.

See also

• Great sample : Proof of aldehydes or reducing functional groups by reducing silver (I) ions to metallic silver
• Cyclopropene : Synthesis of cyclopropene with silver hydroxide and methyl iodide (CH ₃ I)

Individual evidence

1. ^ Jean D'Ans, Ellen Lax: Pocket book for chemists and physicists . Springer DE, 1997, ISBN 3-540-60035-3 , pp. 1057 ( limited preview in Google Book search).
2. ↑ ^{a b} Chemical Abstracts, Volume 95, No. November 19, 1981, Columbus, Ohio, USA, M. MASSACCESI, "Two-phase titration of some quaternary ammonium compounds in the presence of amines or other quaternary ammonium compounds", page 437.
3. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
4. ↑ The Theory of Colloidal Silver
5. ^ ^{A b c} A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1460.
6. ^ George Biedermann, Lars Gunnar Sillén: Studies on the Hydrolysis of Metal Ions. Part 30. A Critical Survey of the Solubility Equilibria of Ag ₂ O. In: Acta Chemica Scandinavica. 1960, 14, p. 717, doi : 10.3891 / acta.chem.scand.14-0717 .
7. ↑ Jander Blasius, textbook on analytical and preparative inorganic chemistry , Stuttgart-Leipzig, 1995, 14th edition
8. ^ Römpp Lexikon Chemie , Vol. 5, 9th edition, p. 4159.
9. ↑ Preparation of halide-free quaternary ammonium salts
10. ↑ C. Paal, On Colloidal Silver , Ber. German Chem. Gesellsch. 35 (1902), pp. 2224-2236.