Periodic acid
| Names | |
|---|---|
| IUPAC name
Periodic acid
| |
| Other names
Hydrogen periodate
Iodic(VII) acid Paraperiodic acid Periodic acid dihydrate (ortho) | |
| Properties | |
| HIO4 (metaperiodic) H5IO6 (orthoperiodic) | |
| Molar mass | 227.941 g/mol (H5IO6) 190.91 g/mol (HIO4) |
| Appearance | Colorless crystals |
| Odor | Odorless |
| Melting point | 128.5 °C (263.3 °F; 401.6 K) |
| Soluble | |
| Solubility | Soluble in alcohols |
| Hazards | |
| Safety data sheet | Sigma-Aldrich (ortho) |
| Flash point | Non-flammable |
| Related compounds | |
| Related compounds
|
Perchloric acid Perbromic acid |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Periodic acid is the highest oxoacid of iodine, in which the iodine exists in oxidation state +7. Like all periodates it can exist in two forms: orthoperiodic acid, with the chemical formula H5IO6 and metaperiodic acid, which has the formula HIO4.
Contents
Properties
Chemical
Heating metaperiodic acid to around 150 °C gives iodine pentoxide (I2O5) rather than the expected anhydride diiodine heptoxide (I2O7), while releasing oxygen as byproduct.[1]
- 2 HIO4 → I2O5 + H2O + O2
Like all periodates periodic acid can be used to cleave various 1,2-difunctional compounds. Most notably periodic acid will cleave vicinal diols into two aldehyde or ketone fragments (Malaprade reaction).
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.
Periodic acid is also used as an oxidizing agent of moderate strength.
Physical
Both orthoperiodic and metaperiodic acid are white colorless crystalline solids, very soluble in water.
Availability
Periodic acid, both the ortho- and the meta- forms can be bought from chemical suppliers.
Preparation
Modern industrial scale production involves the oxidation of a solution of sodium iodate under alkaline conditions, either electrochemically on a PbO2 anode, or by treatment with chlorine:[2]
- IO−
3 + 6 HO−
− 2 e− → IO5−
6 + 3 H2O (counter ions omitted for clarity) E° = ;-1.6 V[3] - IO−
3 + 6 HO−
+ Cl2 → IO5−
6 + 2 Cl− + 3 H2O
Orthoperiodic acid can be dehydrated to give metaperiodic acid by heating to 100 °C under reduced pressure.
- H5IO6 ⇌ HIO4 + 2 H2O
Metaperiodic acid can also be prepared from various orthoperiodates by treatment with dilute nitric acid.[4]
- H5IO6 → HIO4 + 2 H2O
Projects
- Malaprade reaction
- Preparation of iodine pentoxide
Handling
Safety
Periodic acid is irritant, corrosive and mildly oxidizer. Proper protection should be worn when handling the compound.
Storage
In closed airtight bottles, away from moisture and reducing agents.
Disposal
Should be neutralized with a base to the safer periodate salts.
References
- ↑ https://www.bionity.com/en/encyclopedia/Periodic_acid.html
- ↑ https://www.sciencedirect.com/book/9780750633659/chemistry-of-the-elements?via=ihub=
- ↑ https://archive.org/details/ost-chemistry-parsons-handbookofelectrochemicalconstants/page/n41/mode/2up
- ↑ Riley, edited by Georg Brauer; translated by Scripta Technica, Inc. Translation editor Reed F. (1963). Handbook of preparative inorganic chemistry. Volume 1 (2nd ed.). New York, N.Y.: Academic Press. pp. 323–324
