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{{Short description|Chemical compound (Te(OH)6)}}
{{chembox {{chembox
| Verifiedfields = changed
| verifiedrevid = 444134163
| Watchedfields = changed
| ImageFile = Telluric acid.svg
| verifiedrevid = 470481521
| ImageSize = 150px
| ImageName = Telluric acid | ImageFile = Telluric acid.svg
| ImageSize = 150px
| ImageFile1 = Telluric-acid-3D-balls.png
| ImageName = ] of ortho-telluric acid
| ImageSize1 = 150px
| ImageFile1 = Telluric-acid-3D-balls.png
| ImageName1 = Ball-and-stick model of telluric acid
| ImageSize1 = 150px
| IUPACName = Telluric(VI) acid
| ImageName1 = ] of ortho-telluric acid
| OtherNames = orthotelluric acid
| IUPACName = Hexahydroxidotellurium
| Section1 = {{Chembox Identifiers
| OtherNames = {{ubl|Orthotelluric acid|Hexahydroxytellurium|Hexahydroxy-λ<sup>6</sup>-tellane|Tellurium hexahydroxide|Tellurium(VI) hydroxide}}
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 55517 | ChemSpiderID = 55517
| InChI = 1/H2O4Te/c1-5(2,3)4/h(H2,1,2,3,4) | InChI = 1/H2O4Te/c1-5(2,3)4/h(H2,1,2,3,4)
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = XHGGEBRKUWZHEK-UHFFFAOYSA-N | StdInChIKey = XHGGEBRKUWZHEK-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|??}} | CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 7803-68-1 | CASNo = 7803-68-1
| UNII_Ref = {{fdacite|correct|FDA}}
| PubChem = 61609
| RTECS = | UNII = WE1KZR49WU
| PubChem = 62686
| RTECS =
}} }}
| Section2 = {{Chembox Properties |Section2={{Chembox Properties
| Formula = H<sub>6</sub>O<sub>6</sub>Te | Formula = {{chem2|Te(OH)6}}
| Te=1|O=6|H=6
| MolarMass = 229.64 g/mol
| Appearance = White ] crystals | Appearance = White ] crystals
| Density = 3.07 g/cm<sup>3</sup> | Density = 3.07 g/cm<sup>3</sup>
| MeltingPt = 136°C (409.15 K) | MeltingPtC = 136
| MeltingPt_notes =
| BoilingPt =
| pKa = 7.5, 11, 14<ref name=P82db>{{cite book|title=Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution|editor-first=D.&nbsp;D.|editor-last=Perrin|edition=2nd|series=] Chemical Data|issue=29|publisher=Pergamon|location=Oxford|year=1982|publication-date=1984|orig-date=1969|lccn=82-16524|isbn=0-08-029214-3|at=Entry&nbsp;219}}</ref>
| Solubility = 50.1 g/100 ml at 30°C<ref name="hand">
| Solubility = 50.1 g/(100 ml) at 30 °C<ref name=CRC>
{{Citation {{Citation
| last = Lide | last = Lide
| first = David R. | first = David R.
| author-link = | author-link =
| last2 = | year = 1998
| title = Handbook of Chemistry and Physics
| first2 =
| edition = 87
| author2-link =
| volume =
| publication-date =
| date = | series =
| publication-place = Boca Raton, Florida
| year = 1998
| publisher = CRC Press
| title = Handbook of Chemistry and Physics
| edition = 87 | id =
| isbn = 0-8493-0594-2
| volume =
| series = | doi =
| oclc =
| publication-place = Boca Raton, FL
| place = | pages =
| url =
| publisher = CRC Press
| id = | accessdate =
| isbn = 0-8493-0594-2
| doi =
| oclc =
| pages = 4–88
| url =
| accessdate =
}}</ref>
| pKa = 7.68, 11.0 at 18°C<ref name="hand2">
{{Citation
| last = Lide
| first = David R.
| author-link =
| last2 =
| first2 =
| author2-link =
| publication-date =
| date =
| year = 1998
| title = Handbook of Chemistry and Physics
| edition = 87
| volume =
| series =
| publication-place = Boca Raton, FL
| place =
| publisher = CRC Press
| id =
| isbn = 0-8493-0594-2
| doi =
| oclc =
| pages = 8–45
| url =
| accessdate =
}}</ref> }}</ref>
| ConjugateBase = ]
}} }}
| Section3 = {{Chembox Structure |Section3={{Chembox Structure
| MolShape = octahedral | MolShape = octahedral
| CrystalStruct = | CrystalStruct =
| Dipole = 0 ] | Dipole = 0 ]
}} }}
| Section7 = {{Chembox Hazards |Section7={{Chembox Hazards
| ExternalMSDS = | ExternalSDS =
| MainHazards = corrosive | MainHazards = corrosive
| RPhrases = | HPhrases =
| SPhrases = | PPhrases =
| GHS_ref =
}}
}}
| Section8 = {{Chembox Related
|Section8={{Chembox Related
| OtherCations =
| OtherCations =
| OtherAnions = ] <br> ] <br> ]
| OtherCpds = ],<br /> ]<br />] | OtherAnions = ]<br>]<br>]
| OtherCompounds = ]<br />]<br />]
}} }}
}} }}


'''Telluric acid''' is a ] with the ] Te(OH)<sub>6</sub>. It is a white solid made up of octahedral Te(OH)<sub>6</sub> molecules which persist in aqueous solution.<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref> There are two forms, rhombohedral and monoclinic, and both contain octahedral Te(OH)<sub>6</sub> molecules.<ref name = "Cotton">{{Cotton&Wilkinson6th}}</ref> '''Telluric acid''', or more accurately ''']telluric acid''', is a ] with the ] {{chem2|Te(OH)6}}, often written as {{chem2|H6TeO6}}. It is a white crystalline solid made up of octahedral {{chem2|Te(OH)6}} molecules which persist in aqueous solution.<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref> In the solid state, there are two forms, rhombohedral and monoclinic, and both contain octahedral {{chem2|Te(OH)6}} molecules,<ref name = "Cotton">{{Cotton&Wilkinson6th}}</ref> containing one hexavalent ] (Te) atom in the +6 oxidation state, attached to six ] (–OH) groups, thus, it can be called tellurium(VI) hydroxide.
Telluric acid is a ] which is ], forming ] ]s with ]s and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water.<ref name = "Cotton"/><ref>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.</ref> Telluric acid is a ] which is ], forming ] ]s with ]s and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water.<ref name = "Cotton"/><ref name=holleman>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}.</ref> It is used as tellurium-source in the synthesis of oxidation catalysts.

==Preparation== ==Preparation==
Telluric acid is formed by the ] of ] or ] with a powerful oxidising agent such as ], ] or ].<ref name = "Cotton"/> Telluric acid is formed by the ] of ] or ] with a powerful ] such as ], ] or ].<ref name = "Cotton"/>
:TeO<sub>2</sub> + H<sub>2</sub>O<sub>2</sub> + 2H<sub>2</sub>O → Te(OH)<sub>6</sub> :{{chem2|TeO2 + H2O2 + 2 H2O → Te(OH)6}}
Crystallisation of telluric acid solutions below 10°C gives Te(OH)<sub>6</sub>.4H<sub>2</sub>O.<ref name = "Greenwood"/> Crystallization of telluric acid solutions below 10&nbsp;°C gives telluric acid tetrahydrate {{chem2|Te(OH)6*4H2O}}.<ref name = "Greenwood"/>
It is oxidizing, as shown by the ] for the reaction below, although it is kinetically slow in its oxidations.<ref name = "Cotton"/> It is an oxidising agent, as shown by the ] for the reaction below, although it is kinetically slow in its oxidations.<ref name = "Cotton"/>
:H<sub>6</sub>TeO<sub>6</sub> + 2H<sup>+</sup> + 2e<sup>&minus;</sup> {{unicode|&#8652;}} TeO<sub>2</sub> + 4H<sub>2</sub>O ''E''<sup><s>o</s></sup> = +1.02 V :{{chem2|Te(OH)6 + 2 H+ + 2 e- ⇌ TeO2 + 4 H2O}}, ''E''<sup><s>o</s></sup> = +1.02&nbsp;V
Chlorine, by comparison, is +1.36V and selenious acid is +0.74V in oxidizing conditions. ], by comparison, is +1.36&nbsp;V and ] is +0.74&nbsp;V in oxidizing conditions.


==Properties and reactions== ==Properties and reactions==
The anhydrous acid is stable in air at 100°C but above this it dehydrates to form polymetatelluric acid, a white hygroscopic powder (approximate composition (H<sub>2</sub>TeO<sub>4</sub>)<sub>10</sub>), and allotelluric acid, an acid syrup of unknown structure (approximate composition (H<sub>2</sub>TeO<sub>4</sub>)<sub>3</sub>(H<sub>2</sub>O)<sub>4</sub>).<ref name = "Greenwood"/><br /> The anhydrous acid is stable in air at 100&nbsp;°C but above this it dehydrates to form polymetatelluric acid, a white hygroscopic powder (approximate composition {{chem2|(H2TeO4)10}}), and allotelluric acid, an acid syrup of unknown structure (approximate composition {{chem2|3*H2TeO4*4H2O}}).<ref>{{cite journal|doi=10.1107/S0567740879011286|title=Structure of an adduct of orthotelluric acid and urea|journal=Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry|volume=35|issue=12|pages=3039–3041|year=1979|last1=Loub|first1=J.|last2=Haase|first2=W.|last3=Mergehenn|first3=R.|bibcode=1979AcCrB..35.3039L }}</ref><ref name = "Greenwood"/>

Typical salts of the acid contains the anions <sup>-</sup> and <sup>2-</sup>. The presence of the tellurate ion TeO<sub>4</sub><sub>2-</sub> has been confirmed in the solid state structure of Rb<sub>6</sub>.<ref name="InorgChem">.{{cite book
Typical salts of the acid contains the anions {{chem2|−}} and {{chem2|(2−)}}. The presence of the tellurate ion {{chem2|TeO4(2−)}} has been confirmed in the solid state structure of {{chem2|Rb6}}.<ref name="InorgChem">{{cite book
| title = Inorganic Chemistry, 3rd Edition | title = Inorganic Chemistry, 3rd Edition
| chapter = Chapter 16: The group 16 elements | chapter = Chapter 16: The group 16 elements
Line 126: Line 104:
| page = 526 | page = 526
}}</ref> }}</ref>
Strong heating at over 300°C produces the α- crystalline modification of ], α-TeO<sub>3</sub>. Strong heating at over 300&nbsp;°C produces the α crystalline modification of ], α-{{chem2|TeO3}}.
<ref name = holleman/> Reaction with ] gives the hexamethyl ester, {{chem2|Te(OCH3)6}}.<ref name = "Greenwood"/>
<ref name = "Wiberg&Holleman">''Inorganic Chemistry'',Egon Wiberg, Arnold Frederick Holleman Elsevier 2001 ISBN 0-12-352651-5</ref><br />
Reaction with ] gives the hexamethyl ester, Te(OMe)<sub>6</sub>.<ref name = "Greenwood"/>


Telluric acid and its salts mostly contain hexacoordinate ].<ref name = "Cotton"/> This is true even for salts such as magnesium tellurate, MgTeO<sub>4</sub>, which is isostructural with magnesium molybdate and contains TeO<sub>6</sub> octahedra.<ref name = "Cotton"/> Telluric acid and its salts mostly contain hexacoordinate ].<ref name = "Cotton"/> This is true even for salts such as magnesium tellurate, {{chem2|MgTeO4}}, which is isostructural with magnesium molybdate and contains {{chem2|TeO6}} octahedra.<ref name = "Cotton"/>


==Other forms of telluric acid== ==Other forms of telluric acid==
Metatelluric acid, H<sub>2</sub>TeO<sub>4</sub>, the tellurium analogue of ], H<sub>2</sub>SO<sub>4</sub>, is unknown. Allotelluric acid of approximate composition H<sub>2</sub>TeO<sub>4</sub>)<sub>3</sub>(H<sub>2</sub>O)<sub>4</sub>, is not well characterised and may be a mixture of Te(OH)<sub>6</sub> and (H<sub>2</sub>TeO<sub>4</sub>)<sub>n</sub>.<ref name = "Greenwood"/><br /> Metatelluric acid, {{chem2|H2TeO4}}, the tellurium analogue of ], {{chem2|H2SO4}}, is unknown. Allotelluric acid of approximate composition {{chem2|3*H2TeO4*4H2O}}, is not well characterised and may be a mixture of {{chem2|Te(OH)6}} and {{chem2|(H2TeO4)_{''n''}|}}.<ref name = "Greenwood"/>


==Other tellurium acids== ==Other tellurium acids==
], containing tellurium in its +4 oxidation state, (H<sub>2</sub>TeO<sub>3</sub>) is known but not well characterised. ] {{chem2|H2TeO3}}, containing tellurium in its +4 oxidation state, is known but not well characterised.
] is an unstable gas that forms ] upon addition to water. ] is an unstable gas that forms ] upon addition to water.


==References== ==References==
{{reflist}} {{reflist}}

==Sources==
*{{Cotton&Wilkinson6th}}
*{{RubberBible83rd}}


{{Hydrogen compounds}} {{Hydrogen compounds}}
{{Hydroxides}}
{{Authority control}}


] ]
] ]
] ]
] ]

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Latest revision as of 10:04, 27 August 2024

Chemical compound (Te(OH)6)
Telluric acid
Skeletal formula of ortho-telluric acid
Ball-and-stick model of ortho-telluric acid
Names
IUPAC name Hexahydroxidotellurium
Other names
  • Orthotelluric acid
  • Hexahydroxytellurium
  • Hexahydroxy-λ-tellane
  • Tellurium hexahydroxide
  • Tellurium(VI) hydroxide
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.029.334 Edit this at Wikidata
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/H2O4Te/c1-5(2,3)4/h(H2,1,2,3,4)Key: XHGGEBRKUWZHEK-UHFFFAOYSA-N
  • InChI=1/H2O4Te/c1-5(2,3)4/h(H2,1,2,3,4)Key: XHGGEBRKUWZHEK-UHFFFAOYAT
SMILES
  • O(O)(O)(O)(O)O
Properties
Chemical formula Te(OH)6
Molar mass 229.64 g·mol
Appearance White monoclinic crystals
Density 3.07 g/cm
Melting point 136 °C (277 °F; 409 K)
Solubility in water 50.1 g/(100 ml) at 30 °C
Acidity (pKa) 7.5, 11, 14
Conjugate base Tellurate
Structure
Molecular shape octahedral
Dipole moment 0 D
Hazards
Occupational safety and health (OHS/OSH):
Main hazards corrosive
Related compounds
Other anions Hydrotelluric acid
Tellurous acid
Hydrogen telluride
Related compounds Teflic acid
Sulfuric acid
Selenic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). ☒N verify (what is  ?) Infobox references
Chemical compound

Telluric acid, or more accurately orthotelluric acid, is a chemical compound with the formula Te(OH)6, often written as H6TeO6. It is a white crystalline solid made up of octahedral Te(OH)6 molecules which persist in aqueous solution. In the solid state, there are two forms, rhombohedral and monoclinic, and both contain octahedral Te(OH)6 molecules, containing one hexavalent tellurium (Te) atom in the +6 oxidation state, attached to six hydroxyl (–OH) groups, thus, it can be called tellurium(VI) hydroxide. Telluric acid is a weak acid which is dibasic, forming tellurate salts with strong bases and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water. It is used as tellurium-source in the synthesis of oxidation catalysts.

Preparation

Telluric acid is formed by the oxidation of tellurium or tellurium dioxide with a powerful oxidising agent such as hydrogen peroxide, chromium trioxide or sodium peroxide.

TeO2 + H2O2 + 2 H2O → Te(OH)6

Crystallization of telluric acid solutions below 10 °C gives telluric acid tetrahydrate Te(OH)6·4H2O. It is an oxidising agent, as shown by the electrode potential for the reaction below, although it is kinetically slow in its oxidations.

Te(OH)6 + 2 H + 2 e ⇌ TeO2 + 4 H2O, E = +1.02 V

Chlorine, by comparison, is +1.36 V and selenous acid is +0.74 V in oxidizing conditions.

Properties and reactions

The anhydrous acid is stable in air at 100 °C but above this it dehydrates to form polymetatelluric acid, a white hygroscopic powder (approximate composition (H2TeO4)10), and allotelluric acid, an acid syrup of unknown structure (approximate composition 3·H2TeO4·4H2O).

Typical salts of the acid contains the anions [Te(O)(OH)5] and [Te(O)2(OH)4]. The presence of the tellurate ion TeO2−4 has been confirmed in the solid state structure of Rb6[TeO5][TeO4]. Strong heating at over 300 °C produces the α crystalline modification of tellurium trioxide, α-TeO3. Reaction with diazomethane gives the hexamethyl ester, Te(OCH3)6.

Telluric acid and its salts mostly contain hexacoordinate tellurium. This is true even for salts such as magnesium tellurate, MgTeO4, which is isostructural with magnesium molybdate and contains TeO6 octahedra.

Other forms of telluric acid

Metatelluric acid, H2TeO4, the tellurium analogue of sulfuric acid, H2SO4, is unknown. Allotelluric acid of approximate composition 3·H2TeO4·4H2O, is not well characterised and may be a mixture of Te(OH)6 and (H2TeO4)n.

Other tellurium acids

Tellurous acid H2TeO3, containing tellurium in its +4 oxidation state, is known but not well characterised. Hydrogen telluride is an unstable gas that forms hydrotelluric acid upon addition to water.

References

  1. Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, Florida: CRC Press, ISBN 0-8493-0594-2
  2. Perrin, D. D., ed. (1982) . Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 219. ISBN 0-08-029214-3. LCCN 82-16524.
  3. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. ^ Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5
  5. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  6. Loub, J.; Haase, W.; Mergehenn, R. (1979). "Structure of an adduct of orthotelluric acid and urea". Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry. 35 (12): 3039–3041. Bibcode:1979AcCrB..35.3039L. doi:10.1107/S0567740879011286.
  7. Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 16: The group 16 elements". Inorganic Chemistry, 3rd Edition. Pearson. p. 526. ISBN 978-0-13-175553-6.
Hydrogen compounds
Hydroxides
HOH He
LiOH Be(OH)2 B(OH)3 C(OH)4 N(OH)3
[NH4]OH 		O(OH)2 FOH Ne
NaOH Mg(OH)2 Al(OH)3 Si(OH)4 P(OH)3 S(OH)2 ClOH Ar
KOH Ca(OH)2 Sc(OH)3 Ti(OH)2
Ti(OH)3
Ti(OH)4 		V(OH)2
V(OH)3 		Cr(OH)2
Cr(OH)3 		Mn(OH)2 Fe(OH)2
Fe(OH)3 		Co(OH)2 Ni(OH)2 CuOH
Cu(OH)2 		Zn(OH)2 Ga(OH)3 Ge(OH)2 As(OH)3 Se BrOH Kr
RbOH Sr(OH)2 Y(OH)3 Zr(OH)4 Nb Mo Tc(OH)4 Ru Rh(OH)3 Pd AgOH Cd(OH)2 In(OH)3 Sn(OH)2
Sn(OH)4 		Sb(OH)3 Te(OH)6 IOH Xe
CsOH Ba(OH)2 * Lu(OH)3 Hf Ta W Re Os Ir Pt Au(OH)3 Hg(OH)2 TlOH
Tl(OH)3 		Pb(OH)2
Pb(OH)4 		Bi(OH)3 Po At Rn
FrOH Ra(OH)2 ** Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
 
* La(OH)3 Ce(OH)3
Ce(OH)4 		Pr(OH)3 Nd(OH)3 Pm(OH)3 Sm(OH)3 Eu(OH)2
Eu(OH)3 		Gd(OH)3 Tb(OH)3 Dy(OH)3 Ho(OH)3 Er(OH)3 Tm(OH)3 Yb(OH)3
** Ac(OH)3 Th(OH)4 Pa U(OH)2
U(OH)3
UO2(OH)2 		Np(OH)3
Np(OH)4
NpO2(OH)3 		Pu Am(OH)3 Cm(OH)3 Bk Cf Es Fm Md No
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