Pertechnetic acid explained

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.[1] The dark red hygroscopic substance is a strong acid, with a pKa of 0.32,[2] 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 .[3] While fresh HTcO4 is white.[4]

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.[5]

In aqueous solutions the pertechnic acid is complitely dissociated [6] 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.[7]

Density and activity values of pertechnetic acid aqueous solutions at T = 298.15 K are tabulated in.[8]

See also

Notes and References

  1. Book: Schwochau. Klaus. Technetium : Chemistry and radiopharmaceutical applications. 2000. Wiley-VCH. Weinheim [u.a.]. 3-527-29496-1. 127.
  2. Omori. T.. Asahina. K.. Suganuma. H.. Mechanism of the solvent extraction of pertechnetate with tetraphenylarsonium chloride. Journal of Radioanalytical and Nuclear Chemistry. 191. 1. 99–104. 10.1007/BF02035989. 1995. 97175462.
  3. German . Konstantin E. . Fedoseev . Alexander M. . Grigoriev . Mikhail S. . Kirakosyan . Gayane A. . Dumas . Thomas . Den Auwer . Christophe . Moisy . Philippe . Lawler . Keith V. . Forster . Paul M. . Poineau . Frederic . A 70-Year-Old Mystery in Technetium Chemistry Explained by the New Technetium Polyoxometalate [H<sub>7</sub>O<sub>3</sub>]4[Tc<sub>20</sub>O<sub>68</sub>]⋅4H2O . Chemistry – A European Journal . 24 September 2021 . 27 . 54 . 13624–13631 . 10.1002/chem.202102035.
  4. Soderquist . Chuck . Weaver . Jamie . Cho . Herman . McNamara . Bruce . Sinkov . Sergey . McCloy . John . 2019-10-21 . Properties of Pertechnic Acid . Inorganic Chemistry . en . 58 . 20 . 14015–14023 . 10.1021/acs.inorgchem.9b01999 . 1749878 . 0020-1669.
  5. Poineau F, Weck PF, German K, Maruk A, Kirakosyan G, Lukens W, Rego DB, Sattelberger AP, Czerwinski KR . Speciation of heptavalent technetium in sulfuric acid: structural and spectroscopic studies. Dalton Transactions. 2010. 39 . 37. 8616–8619. 10.1039/C0DT00695E . 20730190.
  6. Ustynyuk . Yuri A. . Gloriozov . Igor P. . Zhokhova . Nelly I. . German . Konstantin E. . Kalmykov . Stepan N. . November 2021 . Hydration of the pertechnetate anion. DFT study . Journal of Molecular Liquids . 342 . 117404 . 10.1016/j.molliq.2021.117404 . 0167-7322.
  7. Volkov . Mikhail A. . Novikov . Anton P. . Grigoriev . Mikhail S. . Kuznetsov . Vitaly V. . Sitanskaia . Anastasiia V. . Belova . Elena V. . Afanasiev . Andrey V. . Nevolin . Iurii M. . German . Konstantin E. . January 2023 . 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 . International Journal of Molecular Sciences . en . 24 . 3 . 2015 . 10.3390/ijms24032015 . free . 36768335 . 9916763 . 1422-0067.
  8. Moeyaert . P. . Abiad . L. . Sorel . C. . Dufrêche . J.-F. . Ruas . A. . Moisy . Ph. . Miguirditchian . M. . December 2015 . Density and activity of pertechnetic acid aqueous solutions at T = 298.15 K . The Journal of Chemical Thermodynamics . 91 . 94–100 . 10.1016/j.jct.2015.07.006 . 0021-9614.

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