Hypoiodite

As Hypoiodite are salts of Hypoiodigen acid referred to which the hypoiodite anion IO ^- included. Iodine is in the +1 oxidation state . Hypoiodites are only known in aqueous solution and so far could not be isolated as pure substances in solid form.

Classification

Hypoiodites belong to the substance group of salts of halogenated oxygen acids and thereby to the subgroup of salts of iodinated oxygen acids (with anions of the formula type IO _n ^- with n = 1, 2, 3, 4; with periodates further variants) or to the subgroup of hypohalites (salts of hypohalogens Acids with anions of the formula type XO ^- with X = F, Cl, Br, I, At).

presentation

Hypoiodites can be produced in aqueous solution - analogously to hypochlorites and hypobromites - by reacting elemental iodine I ₂ with alkali lye , resulting in a disproportionation of elemental iodine I ₂ (iodine in oxidation state 0) to iodide I ^- (iodine in oxidation state −1) and Hypoiodit IO ^- (iodine in the +1 oxidation state):

${\displaystyle \mathrm {{\overset {\pm 0}{I}}\!{}_{2}+2\ OH^{-}\ \longrightarrow \ {\overset {-1}{I}}\!{}^{-}+{\overset {+1}{\ I}}\!O^{-}+H_{2}O} }$

When using sodium hydroxide solution , for example, a solution of sodium iodide NaI and sodium hypoiodite NaIO is created:

${\displaystyle \mathrm {I_{2}+2\ NaOH\ \longrightarrow \ NaI+NaIO+H_{2}O} }$

properties

Acid-base behavior

Since hypoiodite acid HIO is only a very weak acid ( p K _S value of 10.64 at 25 ° C), the hypoiodite anion IO ^{- is} a strong base as its corresponding base ( p K _B value = 3, 36) and is therefore only unprotonated in aqueous solutions in the strongly alkaline pH range.

Instability, redox behavior

Hypoiodite in aqueous solution is somewhat more stable than hypoiodous acid, but is also not stable and changes into iodide and iodate in a short time with disproportionation ( iodite IO ₂ ^- also occurs as an intermediate product , the decomposition can be slowed down by low temperatures):

${\displaystyle \mathrm {3\;{\overset {+1}{\ I}}\!O^{-}\ \longrightarrow \ 2\;{\overset {-1}{I}}\!{}^{-}+{\overset {+5}{\ I}}\!O_{3}^{-}} }$

As the tendency to disproportionate shows, the hypoiodite anion IO ^- can react both as an oxidizing agent and as a reducing agent ( redox amphoteric ; redox potentials see under hypoiodous acid ).

See also

Salts of inorganic acids containing iodine

Oxidation level of iodine	−1	+1	+3	+5	+7
Surname	Iodides	Hypoiodite	Iodites	Iodates	Periodates
Formula of the anion	I -	IO -	IO 2 -	IO 3 -	IO 4 - , IO 6 5− and others

Individual evidence

1. ^ ^{A b c} A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. De Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 463–465, 468, 474, 2008 ( limited preview of the 101st edition in Google Book Search).