Hydroxide: Difference between revisions
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In [[chemistry]], '''hydroxide''' is the name for the [[Diatomic molecule|diatomic]] [[anion]] OH<sup>−</sup>, consisting of [[oxygen]] and [[hydrogen]] [[atom]]s, usually derived from the [[Dissociation (chemistry)|dissociation]] of a [[base (chemistry)|base]]. It is one of the simplest and most pervasive diatomic ions known. |
In [[chemistry]], '''hydroxide''' is the name for the [[Diatomic molecule|diatomic]] [[anion]] OH<sup>−</sup>, consisting of [[Covalent bond|covalently bonded]] [[oxygen]] and [[hydrogen]] [[atom]]s, usually derived from the [[Dissociation (chemistry)|dissociation]] of a [[base (chemistry)|base]]. It is one of the simplest and most pervasive diatomic ions known. |
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[[Inorganic]] compounds that contain the [[hydroxyl]] group are referred to as hydroxides. Alkali metal (Li<sup>+</sup>, Na<sup>+</sup>, K<sup>+</sup>) and alkaline earth (Mg<sup>2+</sup>, Ca<sup>2+</sup>, Ba<sup>2+</sup>) salts containing hydroxide are common bases. Common hydroxides include: |
[[Inorganic]] compounds that contain the [[hydroxyl]] group are referred to as hydroxides. Alkali metal (Li<sup>+</sup>, Na<sup>+</sup>, K<sup>+</sup>) and alkaline earth (Mg<sup>2+</sup>, Ca<sup>2+</sup>, Ba<sup>2+</sup>) salts containing hydroxide are common bases. Common hydroxides include: |
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Revision as of 12:38, 30 December 2009
In chemistry, hydroxide is the name for the diatomic anion OH−, consisting of covalently bonded oxygen and hydrogen atoms, usually derived from the dissociation of a base. It is one of the simplest and most pervasive diatomic ions known.
Inorganic compounds that contain the hydroxyl group are referred to as hydroxides. Alkali metal (Li+, Na+, K+) and alkaline earth (Mg2+, Ca2+, Ba2+) salts containing hydroxide are common bases. Common hydroxides include:
- Sodium hydroxide, NaOH
- Potassium hydroxide, KOH
- Calcium hydroxide, Ca(OH)2
Chemical properties
Hydroxide as a base
Hydroxide as nucleophile
Hydroxide is also a strong nucleophile, converting halides to hydroxides. Characteristically hydroxides absorb carbon dioxide to give carbonates and bicarbonates:
- NaOH + CO2 → NaHCO3
Esters are saponified (converted into soap-like products) by the action of hydroxides:
- NaOH + RCO2R' → RCO2Na + R'OH
As a ligand
The hydroxide ion is a kind of ligand. It donates lone pairs of electrons, behaving as a Lewis base. Examples of complexes containing such a ligand include the aluminate ion [Al(OH)4]− and aurate ion [Au(OH)4]−.
Solubility
Many inorganic hydroxide salts are insoluble in water. Exceptions include hydroxide salts of the Group I, Ba2+, Sr2+, Ca2+ (slightly) or Tl+.
Applications
Hydroxides and hydroxide ions are extremely useful and are the coproduct in the large chlor-alkali process. Sodium hydroxide (lye) and potassium hydroxide are particularly large scale intermediates. Many hydroxides are useful minerals such as the aluminium ore bauxite is composed largely of aluminium hydroxides. Goethite and limonite are low grade brown iron ores.
Hydrated hydroxide ion H3O2−
The mono-hydrated hydroxide ion,H3O2−, the bihydroxide ion, has been found in a small number of compounds. The salt Na2[N(C2H5)3CH3][Cr(PhC(S)=N-(O))3].½NaH3O2.18H2O[1] The H3O2− ion in this compound is centrosymmetric and has a very short hydrogen bond, (114.5 pm), which is similar to the length (114 pm) in the bifluoride, HF2− ion.
See also
Notes
- ^ Kamal Abu-Dari, Kenneth N. Raymond, Derek P. Freyberg (1979). "The bihydroxide (H3O2-) anion. A very short, symmetric hydrogen bond". J. Am. Chem. Soc. 101: 3688–3689. doi:10.1021/ja00507a059.
{{cite journal}}: CS1 maint: multiple names: authors list (link)
External links
