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I found various formulae of manganese oxohydroxide. Some site says it is $\ce{MnOOH}$, other say it is, $\ce{MnO(OH)2}$. So, which one is correct?

  1. The mineral manganite is considered manganese oxide-hydroxide $\ce{MnOOH}$, but yahoo answer claims that it is $\ce{MnO(OH)2}$.

  2. In Winkler titration, $\ce{MnO(OH)2}$ is formed:

    $$\ce{2 MnSO4(s) + O2(aq) → 2 MnO(OH)2(s)}$$

There is some uncertainty about whether the oxidised manganese is tetravalent or trivalent. Some sources claim that $\ce{Mn(OH)3}$ is the brown precipitate, but hydrated $\ce{MnO2}$ may also give the brown colour. So, is $\ce{MnO(OH)2}$ hydrated $\ce{MnO2}$?

So which one is manganese oxohydroxide- $\ce{MnOOH}$ or $\ce{MnO(OH)2}$?

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    $\begingroup$ The difference is that one contains $\ce{Mn^{3+}}$ and the other $\ce{Mn^{4+}}$, and they coexist together perfectly fine. $\endgroup$
    – Ivan Neretin
    Commented Jan 24, 2016 at 13:51
  • $\begingroup$ @IvanNeretin Are you sure they contains Manganese ions? Simon's answer says that they are bonded covalently...... $\endgroup$
    – Nilay Ghosh
    Commented Jan 27, 2016 at 12:52
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    $\begingroup$ That's not important. All ionic compounds are in fact partly ionic and partly covalent. You may interpret those +3 and +4 as just the oxidation states. $\endgroup$
    – Ivan Neretin
    Commented Jan 27, 2016 at 12:56

1 Answer 1

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First, the difference the substances is the oxidation number of manganese. In $\ce{MnOOH}$, the oxidation number of manganese is 3+. While in $\ce{MnO(OH)_2}$, the oxidation number for manganese is 4+.

However this doesn't mean $\ce{MnOOH}$ is manganese (III) oxyhydroxide and $\ce{MnO(OH)_2}$ is manganese (IV) oxyhydroxide, not for $\ce{MnO(OH)_2}$ at least. If you move the element around, you will get $\ce{MnO(OH)_2}$ is actually $\ce{H_2MnO_3}$. $\ce{H_2MnO_3}$ is dihydroxy(oxo)manganese which is an acidic substance.

For the question regarding the structure for both substances, I'm sorry that I don't haven't the image but I can describe it (Hope that would do). For $\ce{MnOOH}$, manganese is single bonded with $\ce{OH}$ and manganese is double bonded with oxygen. For $\ce{MnO(OH)_2}$, manganese have two single bonds with both of the $\ce{OH}$ and manganese is double bonded with oxygen.

In conclusion, $\ce{MnOOH}$ is manganese (III) oxyhydroxide and $\ce{MnO(OH)_2}$ is dihydroxy(oxo)manganese. In structure wise, manganese is single bonded with $\ce{OH}$ and manganese is double bonded with oxygen for $\ce{MnOOH}$. For $\ce{MnO(OH)_2}$, it likes $\ce{MnOOH}$ but have one more single bond with $\ce{OH}$.

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    $\begingroup$ I understood your explanation but a picture would have been better. Actually, I need a visualization. $\endgroup$
    – Nilay Ghosh
    Commented Jan 25, 2016 at 8:29
  • $\begingroup$ I will find it for you or draw it $\endgroup$
    – Simon-Nail-It
    Commented Jan 25, 2016 at 8:41
  • $\begingroup$ Are the compounds covalently bonded? Ivan (see comment) says it contains manganese ions..... Also in this site , the empirical formula mentioned is Mn3+OOH $\endgroup$
    – Nilay Ghosh
    Commented Jan 27, 2016 at 12:50
  • $\begingroup$ What I assume is that is the manganese oxidation state instead of ion. But I will hope there is more people more expert in this topic may help you. $\endgroup$
    – Simon-Nail-It
    Commented Jan 27, 2016 at 13:10
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    $\begingroup$ dihydroxy(oxo)manganese or manganous acid is actually a hypothetical compound. $\endgroup$
    – Nilay Ghosh
    Commented Mar 9, 2019 at 15:51

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