Orthoperiodic acid can be dehydrated to give metaperiodic acid by heating to 100 °C under reduced pressure.
H5IO6 ⇌ HIO4 + 2 H2O
Further heating to around 150 °C gives iodine pentoxide (I2O5) rather than the expected anhydridediiodine heptoxide (I2O7). Metaperiodic acid can also be prepared from various orthoperiodates by treatment with dilute nitric acid.[6]
There being two forms of periodic acid, it follows that two types of periodate salts are formed. For example, sodium metaperiodate, NaIO4, can be synthesised from HIO4 while sodium orthoperiodate, Na5IO6 can be synthesised from H5IO6.
Orthoperiodic acid forms monoclinic crystals (space group P21/n) consisting of a slightly deformed IO6 octahedron interlinked via bridging hydrogens. Five I–O bond distances are in the range 1.87–1.91 Å and one I–O bond is 1.78 Å.[9][10]
The structure of metaperiodic acid also includes IO6 octahedra, however these are connected via cis-edge-sharing with bridging oxygens to form one-dimensional infinite chains.[11]
This can be useful in determining the structure of carbohydrates as periodic acid can be used to open saccharide rings. This process is often used in labeling saccharides with fluorescent molecules or other tags such as biotin. Because the process requires vicinal diols, periodate oxidation is often used to selectively label the 3′-termini of RNA (ribose has vicinal diols) instead of DNAasdeoxyribose does not have vicinal diols.
Periodate is part of a series of oxyacids in which iodine can assume oxidation states of −1, +1, +3, +5, or +7. A number of neutral iodine oxides are also known.
^Aylett, founded by A.F. Holleman; continued by Egon Wiberg; translated by Mary Eagleson, William Brewer; revised by Bernhard J. (2001). Inorganic chemistry (1st English ed., [edited] by Nils Wiberg. ed.). San Diego, Calif. : Berlin: Academic Press, W. de Gruyter. p. 453. ISBN0123526515.{{cite book}}: CS1 maint: multiple names: authors list (link)
^Riley (1963). Brauer, Georg (ed.). Handbook of preparative inorganic chemistry. Volume 1. Translated by Scripta Technica, Inc. Translation editor Reed F. (2nd ed.). New York, N.Y.: Academic Press. pp. 323–324. ISBN012126601X.
^Aylett, founded by A.F. Holleman; continued by Egon Wiberg; translated by Mary Eagleson, William Brewer; revised by Bernhard J. (2001). Inorganic chemistry (1st English ed., [edited] by Nils Wiberg. ed.). San Diego, Calif. : Berlin: Academic Press, W. de Gruyter. p. 454. ISBN0123526515.{{cite book}}: CS1 maint: multiple names: authors list (link)
^Burgot, Jean-Louis (2012-03-30). Ionic equilibria in analytical chemistry. New York: Springer. p. 358. ISBN978-1441983824.
^Feikema, Y. D. (10 June 1966). "The crystal structures of two oxy-acids of iodine. I. A study of orthoperiodic acid, H5IO6, by neutron diffraction". Acta Crystallographica. 20 (6): 765–769. doi:10.1107/S0365110X66001828.
^Fábry, J.; Podlahová, J.; Loub, J.; Langer, V. (1982). "Structure of the 1:1 adduct of orthoperiodic acid and urea". Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry. 38 (3): 1048–1050. doi:10.1107/S0567740882004932.
^Kraft, Thorsten; Jansen, Martin (1 September 1997). "Crystal Structure Determination of Metaperiodic Acid, HIO4, with Combined X-Ray and Neutron Diffraction". Angewandte Chemie International Edition in English. 36 (16): 1753–1754. doi:10.1002/anie.199717531.
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