Borate

Borate

Borates in chemistry are chemical compounds containing boron bonded to three oxygen atoms written as B(OR)3. In B(OR)4 anions, this number increases to four.

The borate ion is BO33−. it forms salts with metallic elements. Boron found in nature is commonly as a borate mineral. Boron is also found combined with silicate to form complex borosilicate minerals such as the tourmalines.

Overview

Borate exists in many forms. In acid and near-neutral conditions, it is boric acid, commonly written as H3BO3 but more correctly B(OH)3. The p"K"a of boric acid is 9.14 at 25C. Boric acid does not dissociate in aqueous solution, but is acidic due to its interaction with water molecules, forming tetrahydroxyborate:

::B(OH)3 + H2O unicode|⇌ B(OH)4 + H+:::"K"a = 5.8x10−10 mol/l; p"K"a = 9.24.

Polyborate anions are formed at pH 7–10 if the boron concentration is higher than about 0.025 mol/L. The best known of these is the tetraborate ion, found in the mineral borax:::4B(OH)4 + 2H+ ⇌ B4O72− + 9H2O

Even though boric acid adds hydroxide to form B(OH)4, you may find for pKa values and other calculations, the fictitious ions are easier to use. Thus for a typical polyprotic acid, the deprotonation series dihydrogen borate [H2BO3−;] , hydrogen borate [HBO32−] and borate [BO33−] may be written as pH increases.

Polymeric ions

Boric acid can be used to form many polymeric ions. The tetraborate ion, B4O72−, is very common; the hydrogen tetraborate ion, HB4O7, as well as triborate and pentaborate, are also seen. The various metaborate ions have an "empirical" formula of BO2, and form metaborate compounds. Formation of these complicated, potentially infinite network structures is extensive, perhaps surpassed only by the silicates.

Common borate salts

Common borate salts include sodium metaborate, NaBO2, and sodium tetraborate, Na2B4O7. The latter also occurs naturally as the hydrous mineral borax, Na2B4O7·10H2O. Boron, California contains large borax deposits and is used extensively for borate mining. The Atacama Desert in Chile also contains mineable borate concentrations. Gerry, New York has been described by Agapito Associates Inc. as a "very nice place to mine for [borate] " although it is uncertain how much damage that might do to the surrounding area.

Various forms of borate are used as wood preservatives or fungicides such as disodium octaborate tetrahydrate.

Borate esters

Borate esters are organic compounds of the type B(OR)3 where R is an organic residue (for example alkyl or aryl). Borate esters include trimethyl borate, B(OCH3)3, which is used as a precursor to boronic esters for Suzuki couplings.

External links

* [http://npic.orst.edu/hottopic/AltCCA.pdf Non-CCA Wood Preservatives: Guide to Selected Resources - National Pesticide Information Center]


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Look at other dictionaries:

  • borate — [ bɔrat ] n. m. • 1787; du rad. de borax ♦ Sel ou ester de l acide borique. Borate de magnésium. Borate de sodium. ⇒ borax, tincal. ● borate nom masculin Sel ou ester de l acide borique. (Les borates naturels les plus importants sont le borax, la …   Encyclopédie Universelle

  • Borate — sind Salze oder Ester der Borsäuren. Die Salze sind dadurch gekennzeichnet, dass sie in ihrem Ionengitter als Anion das Borat Ion BO33 bzw. eine kondensierte Form davon (z. B. B4O5(OH)42 , Tetraborat) enthalten. Borate bilden eine… …   Deutsch Wikipedia

  • boraté — boraté, ée (bo ra té, tée) adj. Terme de chimie. Qui contient de l acide borique. Magnésie boratée. ÉTYMOLOGIE    Borate …   Dictionnaire de la Langue Française d'Émile Littré

  • Borate — Bo rate, n. [From {Boric}.] (Chem.) A salt formed by the combination of boric acid with a base or positive radical. [1913 Webster] …   The Collaborative International Dictionary of English

  • Borāte — Borāte, Borsäuresalze, z. B. Natriumborat, borsaures Natron …   Meyers Großes Konversations-Lexikon

  • Borate — sind Salze der Borsäure, von denen einige natürlich vorkommen (s. Borax), andre künstlich dargestellt werden (s. Borax und Borsaures Manganoxydul). Doppelborate verdanken ihre Entstehung der Eigenschaft des geschmolzenen Boraxes, auf Metalloxyde… …   Lexikon der gesamten Technik

  • Borate — Borāte, die Salze der Borsäure …   Kleines Konversations-Lexikon

  • Borate — Borate,   Singular Borat das, s, Salze der Borsäure (Borverbindungen).   …   Universal-Lexikon

  • borate — [bôr′āt΄] n. a salt or ester of boric acid vt. borated, borating to treat or mix with borax or boric acid …   English World dictionary

  • Borate — Un borate est un composé de bore et d oxygène avec des éléments électropositifs. L ion borate est BO33 . Le bore trouvé dans la nature est toujours sous la forme d un borate. Parfois, il est combiné à un silicate pour former un borosilicate. L… …   Wikipédia en Français

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