Pertechnetic acid

{{Chembox

| IUPACName = Pertechnetic acid

| ImageFile = File:Pertechnetic acid 3D ball.png

|Section1={{Chembox Identifiers

| PubChem = 11805084

| CASNo = 14332-45-7

| ChemSpiderID = 9979749

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| SMILES = O[Tc](=O)(=O)=O

| StdInChI = 1S/H2O.3O.Tc/h1H2;;;;/q;;;;+1/p-1

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = UTQISYNNAQMRBN-UHFFFAOYSA-M

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

}}

|Section2={{Chembox Properties

| H=1 | Tc=1 | O=4

| MolarMass = {{chem molar mass|H=1|Tc=1|O=4}}

| ConjugateBase = Pertechnetate

}}

|Section3={{Chembox Related

| OtherFunction_label =

| OtherAnions = Permanganic acid
Perrhenic acid

| OtherCations = Sodium pertechnetate

| OtherCompounds = Perchloric acid

| OtherFunction =

}}

}}

Pertechnetic acid (HTcO₄) is a compound of technetium that is produced by reacting technetium(VII) oxide (Tc₂O₇) with water or reacting Tc metal or TcO2 with strong oxidizing acids, such as nitric acid, mixture of concentrated sulfuric acid with hydrogen peroxide or aqua regia.{{cite book|last1=Schwochau|first1=Klaus|title=Technetium : Chemistry and radiopharmaceutical applications|date=2000|publisher=Wiley-VCH|location=Weinheim [u.a.]|isbn=3-527-29496-1|page=127}} The dark red hygroscopic substance is a strong acid, with a pK_a of 0.32,{{cite journal|last1=Omori|first1=T.|last2=Asahina|first2=K.|last3=Suganuma|first3=H.|title=Mechanism of the solvent extraction of pertechnetate with tetraphenylarsonium chloride|journal=Journal of Radioanalytical and Nuclear Chemistry|volume=191|issue=1|pages=99–104|doi=10.1007/BF02035989|year=1995|s2cid=97175462}} as such it exists almost entirely as the pertechnetate ion in aqueous solution. The red color in solution is thought to be due to the formation of the polyoxometallate {{chem2|Tc20O68(4-)}},{{cite journal |last1=German |first1=Konstantin E. |last2=Fedoseev |first2=Alexander M. |last3=Grigoriev |first3=Mikhail S. |last4=Kirakosyan |first4=Gayane A. |last5=Dumas |first5=Thomas |last6=Den Auwer |first6=Christophe |last7=Moisy |first7=Philippe |last8=Lawler |first8=Keith V. |last9=Forster |first9=Paul M. |last10=Poineau |first10=Frederic |title=A 70-Year-Old Mystery in Technetium Chemistry Explained by the New Technetium Polyoxometalate [H₇O₃]₄[Tc₂₀O₆₈]⋅4H₂O |journal=Chemistry – A European Journal |date=24 September 2021 |volume=27 |issue=54 |pages=13624–13631 |doi=10.1002/chem.202102035}} while fresh HTcO₄ is white.{{Cite journal |last1=Soderquist |first1=Chuck |last2=Weaver |first2=Jamie |last3=Cho |first3=Herman |last4=McNamara |first4=Bruce |last5=Sinkov |first5=Sergey |last6=McCloy |first6=John |date=2019-10-21 |title=Properties of Pertechnic Acid |url=https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b01999 |journal=Inorganic Chemistry |language=en |volume=58 |issue=20 |pages=14015–14023 |doi=10.1021/acs.inorgchem.9b01999 |osti=1749878 |issn=0020-1669}}

Use of strong enough acid solution, for example, concentrated sulfuric acid, can generate the protonated form, which then exists as the octahedral TcO₃(OH)(H₂O)₂ dihydrate complex.{{cite journal|vauthors=Poineau F, Weck PF, German K, Maruk A, Kirakosyan G, Lukens W, Rego DB, Sattelberger AP, Czerwinski KR |title= Speciation of heptavalent technetium in sulfuric acid: structural and spectroscopic studies|journal= Dalton Transactions|year= 2010|volume= 39 |issue=37|pages=8616–8619|doi=10.1039/C0DT00695E |url=http://radchem.nevada.edu/docs/pub/tc%20in%20h2so4%20%28dalton%29%202010-08-23.pdf|pmid=20730190}}

In aqueous solutions the pertechnic acid is complitely dissociated {{Cite journal |last1=Ustynyuk |first1=Yuri A. |last2=Gloriozov |first2=Igor P. |last3=Zhokhova |first3=Nelly I. |last4=German |first4=Konstantin E. |last5=Kalmykov |first5=Stepan N. |date=November 2021 |title=Hydration of the pertechnetate anion. DFT study |url=https://doi.org/10.1016/j.molliq.2021.117404 |journal=Journal of Molecular Liquids |volume=342 |pages=117404 |doi=10.1016/j.molliq.2021.117404 |issn=0167-7322}} and therefore it is considered as very strong acid its deviation from ideal activity being due to ion pair and triple ion formation with counter-cation of hydronium.{{Cite journal |last1=Volkov |first1=Mikhail A. |last2=Novikov |first2=Anton P. |last3=Grigoriev |first3=Mikhail S. |last4=Kuznetsov |first4=Vitaly V. |last5=Sitanskaia |first5=Anastasiia V. |last6=Belova |first6=Elena V. |last7=Afanasiev |first7=Andrey V. |last8=Nevolin |first8=Iurii M. |last9=German |first9=Konstantin E. |date=January 2023 |title=New Preparative Approach to Purer Technetium-99 Samples—Tetramethylammonium Pertechnetate: Deep Understanding and Application of Crystal Structure, Solubility, and Its Conversion to Technetium Zero Valent Matrix |journal=International Journal of Molecular Sciences |language=en |volume=24 |issue=3 |pages=2015 |doi=10.3390/ijms24032015 |doi-access=free |pmid=36768335 |pmc=9916763 |issn=1422-0067}}

Density and activity values of pertechnetic acid aqueous solutions at T = 298.15 K are tabulated in.{{Cite journal |last=Moeyaert |first=P. |last2=Abiad |first2=L. |last3=Sorel |first3=C. |last4=Dufrêche |first4=J.-F. |last5=Ruas |first5=A. |last6=Moisy |first6=Ph. |last7=Miguirditchian |first7=M. |date=December 2015 |title=Density and activity of pertechnetic acid aqueous solutions at T = 298.15 K |url=https://doi.org/10.1016/j.jct.2015.07.006 |journal=The Journal of Chemical Thermodynamics |volume=91 |pages=94–100 |doi=10.1016/j.jct.2015.07.006 |issn=0021-9614}}