Utente:Grasso Luigi/sanbox1/Ossido di iodio

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Iodine pentoxide (I2O5)

Gli ossidi di iodio sono composti chimici di ossigeno e iodio. Lo iodio ha solo due ossidi stabili che sono isolabili in laboratorio, il tetrossido di iodio e il pentossido di iodio, ma si formano pure un certo numero di altri ossidi in tracce o se ne è ipotizzata l'esistenza. La chimica di questi composti è complicata e solo pochi sono stati ben caratterizzati. Molti sono stati rilevati nell'atmosfera e si ritiene che siano particolarmente importanti nello strato limite marino.[1]

Ossidi dello iodio[2]
Formula molecolare I2O IO[3] IO2 I2O4 I2O5 I4O9
Nome diiodine oxide iodine monoxide iodine dioxide iodine tetroxide

(diiodine tetroxide)

Iodine pentoxide

(diiodine pentoxide)

tetraiodine nonoxide
Struttura I2O IO IO2 (IO2)2 O(IO2)2 I(OIO2)3
Modello molecolare
Numero CAS 39319-71-6 14696-98-1 13494-92-3 1024652-24-1 12029-98-0 66523-94-2
Apparenza Unknown purple gas yellow solid yellow solid white crystalline solid dark yellow solid
Stato di ossidazione +1 +2 +4 +3 and +5 +5 +3 and +5
Punto di fusione not isolable not isolable not isolable decomp. 100 °C decomp. 300–350 °C decomp. 75 °C
Gravità specifica 4.2 4.8
Solubilità in acqua decomp. to HIO3 + I2 187 g/100 mL decomp. to HIO3 + I2

Diiodine monoxide has largely been the subject of theoretical study,[4] but there is some evidence that it may be prepared in a similar manner to dichlorine monoxide, via a reaction between HgO and I2.[5] The compound appears to be highly unstable but can react with alkenes to give halogenated products.[6]

Radical iodine oxide (IO), iodine dioxide (IO2) and iodine tetroxide ((IO2)2) all possess significant and interconnected atmospheric chemistry. They are formed, in very small quantities, at the marine boundary layer by the photooxidation of diiodomethane, which is produced by macroalga such as seaweed or through the oxidation of molecular iodine, produced by the reaction of gaseous ozone and iodide present at the seasurface.[7][8] Despite the small quantities produced (typically below ppt) they are thought to be powerful ozone depletion agents.[9][10]

Diiodine pentoxide (I2O5) is the anhydride of iodic acid and the only stable anhydride of an iodine oxoacid.

Tetraiodine nonoxide (I4O9) has been prepared by the gas-phase reaction of I2 with O3 but has not been extensively studied.[11]

Iodate anions

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Iodine oxides also form negatively charged anions, which (associated with complementary cations) are components of acids or salts. These include the iodates and periodates.

Their conjugate acids are:

Iodine oxidation state −1 +1 +3 +5 +7
Name Hydrogen iodide* Hypoiodous acid Iodous acid Iodic acid Periodic acid
Formula HI HIO HIO2 HIO3 HIO4 or H5IO6

*The -1 oxidation state, hydrogen iodide, is not an oxide, but it is included in this table for completeness.

The periodates include two variants: metaperiodate IO−4 and orthoperiodate IO5−6.

Note

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  1. ^ Quantum chemical calculations on a selection of iodine-containing species (IO, OIO, INO3, (IO)2, I2O3, I2O4 and I2O5) of importance in the atmosphere, in Physical Chemistry Chemical Physics, vol. 10, n. 13, 2008, pp. 1723–33, DOI:10.1039/B715687C.
  2. ^ (EN) Lide, D. R. (a cura di), CRC Handbook of Chemistry and Physics, 86ª ed., Boca Raton (Florida, USA), CRC Press, 2005, ISBN 0-8493-0486-5.
  3. ^ Halogen monoxides, in Russian Chemical Reviews, vol. 77, n. 8, 31 August 2008, pp. 739–749, DOI:10.1070/RC2008v077n08ABEH003788.
  4. ^ <383::AID-HC6>3.0.CO;2-9 Theoretical study of I2O, in Heteroatom Chemistry, vol. 9, n. 4, 1998, pp. 383–385, DOI:10.1002/(SICI)1098-1071(1998)9:4<383::AID-HC6>3.0.CO;2-9.
  5. ^ Hypoiodite reaction: kinetic study of the reaction of 1,1-diphenyl-ethylene with mercury(II) oxide iodine, in Journal of the Chemical Society, Perkin Transactions 1, 1974, pp. 2350–2353, DOI:10.1039/P19740002350.
  6. ^ Reactions of iodine oxide with alkenes, in Journal of the Chemical Society, Perkin Transactions 1, n. 18, 1976, p. 1961, DOI:10.1039/P19760001961.
  7. ^ Iodine oxide homogeneous nucleation: An explanation for coastal new particle production (PDF), in Geophysical Research Letters, vol. 28, n. 10, 15 May 2001, pp. 1949–1952, DOI:10.1029/2000GL012399.
  8. ^ Atmospheric iodine levels influenced by seasurface emissions of inorganic iodine (PDF), in Nature Geoscience, vol. 6, n. 2, 13 January 2013, pp. 108–111, DOI:10.1038/ngeo1687.
  9. ^ Iodine chemistry in the troposphere and its effect on ozone, in Atmospheric Chemistry and Physics, vol. 14, n. 23, 10 December 2014, pp. 13119–13143, DOI:10.5194/acp-14-13119-2014.
  10. ^ OIO and the atmospheric cycle of iodine (PDF), in Geophysical Research Letters, vol. 26, n. 13, 1º July 1999, pp. 1857–1860, DOI:10.1029/1999GL900439.
  11. ^ Raman spectra of I4O9 formed by the reaction of iodine with ozone, in Journal of Raman Spectroscopy, vol. 16, n. 6, December 1985, pp. 424–426, DOI:10.1002/jrs.1250160611.

Voci correlate

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