Periodate

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Periodate
The metaperiodate ion
The metaperiodate ion
The orthoperiodate ion
The orthoperiodate ion
Names
Systematic IUPAC name
tetraoxoiodate(1−)
hexaoxoiodate(5−)
Identifiers
3D model (
JSmol
)
ChemSpider
UNII
  • metaperiodate: InChI=1S/HIO4/c2-1(3,4)5/h(H,2,3,4,5)/p-1
    Key: KHIWWQKSHDUIBK-UHFFFAOYSA-M
  • orthoperiodate: InChI=1S/H5IO6/c2-1(3,4,5,6)7/h(H5,2,3,4,5,6,7)/p-5
    Key: TWLXDPFBEPBAQB-UHFFFAOYSA-I
  • Metaperiodate: [O-][I+3]([O-])([O-])[O-]
  • Orthoperiodate: [O-][I+]([O-])([O-])([O-])([O-])[O-]
Properties
IO4− or IO65-
Conjugate acid
 Periodic acid
Related compounds
Other anions
 Perchlorate
Perbromate
Permanganate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Periodate (

counter ions to form periodates, which may also be regarded as the salts of periodic acid
.

Periodates were discovered by Heinrich Gustav Magnus and C. F. Ammermüller; who first synthesised periodic acid in 1833.[1]

Synthesis

Classically, periodate was most commonly produced in the form of sodium hydrogen periodate (Na3H2IO6).[2] This is commercially available, but can also be produced by the oxidation of iodates with chlorine and sodium hydroxide.[3] Or, similarly, from iodides by oxidation with bromine and sodium hydroxide:

Modern industrial scale production involves the

electrochemical oxidation of iodates, on a lead dioxide (PbO2) anode, with the following standard electrode potential
:

     E° = 1.6 V[4]

Metaperiodates are typically prepared by the dehydration of sodium hydrogen periodate with nitric acid,[2] or by dehydrating orthoperiodic acid by heating it to 100 °C under vacuum.

They can also be generated directly from iodates by treatment with other strong oxidizing agents such as hypochlorites:

Forms and interconversion

Periodate can exist in a variety of forms in aqueous media, with pH being a controlling factor. Orthoperiodate has a number of acid dissociation constants.[5][6]

     pKa = 3.29
     pKa = 8.31
     pKa = 11.60

The ortho- and metaperiodate forms also exist in equilibrium.

      K = 29

For this reason orthoperiodate is sometimes referred to as the dihydrate of metaperiodate,[7] written IO−4·2H2O; however, this description is not strictly accurate as X-ray crystallography of H5IO6 shows 5 equivalent I−OH groups.[8]

At extremes of pH additional species can form. Under basic conditions a dehydration reaction can take place to form the diperiodate (sometimes referred to as mesoperiodate).

      K = 820

Under strongly acid conditions periodic acid can be protonated to give the orthoperiodonium cation.[9]

      pKa = −0.8

Structure and bonding

In both the ortho- and metaperiodate the iodine is

dative bonds, confirming the absence of double bonding in these molecules.[10]

Exact structures vary depending on counter ions, however on average orthoperiodates adopt a slightly deformed octahedral geometry with

Å.[11][8] Metaperiodates adopt a distorted tetrahedral geometry with an average I–O distance of 1.78 Å.[12][13]

Reactions

Cleavage reactions

Periodates can cleave carbon–carbon bonds on a variety of 1,2-difunctionalised alkanes.

diol cleavage, which was also the first to be discovered (Malaprade reaction).[16]
In addition to
α-hydroxy acids, amino acids,[17] 1,2-amino alcohols,[18] and 1,2-diamines,[19]
to give aldehydes, ketones, and carboxylic acids. In the presence of strong acid catalyst, like H2SO4 or HNO3 epoxides[20][21] are also converted into aldehyde or ketones or dicarbonyl compounds.

Alkenes can also be oxidised and cleaved in the Lemieux–Johnson oxidation. This uses a catalytic loading of osmium tetroxide which is regenerated in situ by the periodate. The overall process is equivalent to that of ozonolysis.

Cleavage reactions proceed via a cyclic intermediate called a periodate ester. The formation of this may be affected by pH and temperature

lead tetraacetate which reacts in a similar manner and is soluble in organic solvents (Criegee oxidation
).

Periodate cleavage is often utilized in molecular biochemistry for the purposes of modifying

saccharide rings, as many five- and six-membered sugars have vicinal diols. Historically it was also used to determine the structure of monosaccharides.[24][25]

Periodate cleavage may be performed on an industrial scale to form dialdehyde starch which has uses in paper production.[26]

Oxidation reactions

Periodates are powerful

oxidising agents. They can oxidise catechol to 1,2-benzoquinone and hydroquinone to 1,4-benzoquinone.[27] Sulfides can be effectively oxidised to sulfoxides.[28] Periodates are sufficiently powerful to generate other strong inorganic oxidisers such as permanganate,[29] osmium tetroxide[30]
and ruthenium tetroxide.

Niche uses

Periodates are highly selective etchants for certain ruthenium-based oxides.[31]

Several staining agents use in microscopy are based around periodate (e.g. periodic acid–Schiff stain and Jones' stain).

Periodates have also been used as oxidising agents for use in

sodium metaperiodate for use in their tracer ammunition.[33]

Other oxyanions

Periodate is part of a series of oxyanions in which iodine can assume oxidation states of −1, +1, +3, +5, or +7. A number of neutral iodine oxides are also known.

Iodine oxidation state −1 +1 +3 +5 +7
Name iodide
hypoiodite
 iodite iodate periodate
Formula I− IO− IO−
2 		IO−
3 		IO−
4 or IO5−
6
Structure The iodide ion The hypoiodite ion The iodate ion The orthoperiodate ionThe metaperiodate ion

See also

References

  1. doi:10.1002/andp.18331040709
    .
  2. ^
    ISBN 012126601X
    .
  3. doi:10.1021/ja01397a013
    .
  4. ^ Parsons, Roger (1959). Handbook of electrochemical constants. Butterworths Scientific Publications Ltd. p. 71.
  5. ISBN 0123526515.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  6. ISBN 978-1441983824
    .
  7. ISBN 978-0444595539
    .
  8. ^
    doi:10.1107/S0365110X66001828
    .
  9. ISBN 0750633654
    .
  10. PMID 25045143
    .
  11. doi:10.1107/S0567740880005225
    .
  12. doi:10.1107/S0108270199099394
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  13. doi:10.1107/S0567740870004880
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  14. doi:10.1039/QR9672100003
    .
  15. ISBN 9780080868011
    .
  16. Bull. Soc. Chim. Fr.
    3, 1, 833 (1934)
  17. PMID 14342227
    .
  18. doi:10.1021/ja01875a521
    .
  19. doi:10.1039/P29800000039
    .
  20. S2CID 97403497
    .
  21. doi:10.1021/ac60069a047
    .
  22. doi:10.1039/J29710002128
    .
  23. ISBN 978-0840054531
    .
  24. doi:10.1021/ja01285a010
    .
  25. ISBN 0387949518
    .
  26. doi:10.1016/j.carbpol.2009.08.005
    .
  27. doi:10.1021/ja00976a024
    .
  28. doi:10.1021/jo01048a504
    .
  29. doi:10.1139/v55-208
    .
  30. ISSN 0022-3263
    .
  31. ^ Dieter Weber, Róza Vöfély, Yuehua Chen, Yulia Mourzina, Ulrich Poppe: Variable resistor made by repeated steps of epitaxial deposition and lithographic structuring of oxide layers by using wet chemical etchants. Thin Solid Films (2013) DOI: 10.1016/j.tsf.2012.11.118
  32. PMID 22639415
    .
  33. ^ "Picatinny to remove tons of toxins from lethal rounds". U.S. Army. Retrieved 31 October 2013.
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