kmno4
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Oxidation state of N in R-NO2
That is rigth !
What is oxidation state of nitrogen in aliphatic/aromatic nitro compounds ?
I would like to know your opinion....
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solo
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N=+3 as NO2 acts as -NO2
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JohnWW
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It is 5, with the N having 4 covalent and one ionic bond (losing an electron to have a positive charge), to have a filled outer shell of 8 s and p
electrons in sp2 hybridization. The bonding is: C-N(+)(=O)O(-), with the double bonding and negative charge alternating through resonance between the
two Os.
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Magpie
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This is an interesting question. Here's my 2 cents worth:
For nitro compounds like nitrobenzene (Ar-NO2) and nitroglycerine (R-O-NO2) the valence for N would be +5. N would have a double bond with one O and
a coordinate covalent bond with another O. N would have a +1 formal charge, and one O would have a formal charge of -1, since N supplies both e- for
the coordinate covalent bond.
For nitrous acid (HNO2), however, the N would have a valence of +3. Writing it as HONO might show this better.
Ethyl nitrite, C2H5-O-NO, has N with a valence of +3. Whereas for its isomer, nitroethane, C2H5NO2, N would have a valence of +5.
The single most important condition for a successful synthesis is good mixing - Nicodem
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The_Davster
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As NO2+ is used in nitration to introduce nitro groups to aromatic groups, and electron density comes from the aromatic ring I too think it is 5+.
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I am a fish
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In my opinion, the question highlights the limitations of the concept of valency.
Valency is defined by IUPAC as:
"The maximum number of univalent atoms that may combine with an atom of the element under consideration, or with a fragment, or for which an atom
of this element can be substituted."
This definition implicitly assumes that each atom within a molecule is a discrete object, and that the atoms are connected together by well defined
bonds. In reality this is entirely false. There are no true atoms within a molecule; instead there are atomic nuclei surrounded by a probabilistic
cloud of electrons that can only be properly described using quantum mechanics. Without discrete atoms you can't truly say what is bonded to what,
and so the concept of valency is—on a fundamental level—meaningless.
1f `/0u (4|\\| |234d 7|-|15, `/0u |234||`/ |\\|33d 70 937 0u7 /\\/\\0|23.
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Magpie
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Mr Fish, I have confidence that at "a fundamental level" you are correct.
Notwithstanding IUPAC, the definition of valence that I was most recently taught is : "Valence is the number of e- the atom loses, gains, or shares
in making bonds." This is a useful operative definition. Useful for determining such things as formal charge on an atom and whether an atom has been
oxidized, reduced, or left unchanged.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Pyrovus
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It is important not to confuse valency and oxidation number. Valency is a measure of the total number of covalent and/or ionic bonds formed by an atom
in a compound; oxidation number is a measure of whether the atom can be said to have gained or lost control of electrons as a result of these bonds.
For each bond an atom forms, if the bond is to a less electronegative atom, this will decrease the oxidation number by one, and if it is to a more
electronegative atom, it increases the oxidation number by one.
As a result, the oxidation number of an atom (ignoring sign) in a compound will always be less than or equal to its valency.
Methylene chloride (CH2Cl2), for instance has a valency of 4, but an oxidation number of zero.
In the case of R-NO2, the oxidation number of nitrogen is +3. It is doubly bonded to one oxygen and singly bonded to another, meaning that since
oxygen is more electronegative than nitrogen it will have lost control of three electrons. As the nitrogen has a formal charge of +1, this consitutes
the loss of control of one further electron. Finally, in the C-N bond the nitrogen atom has gained control of one electron as nitrogen is more
electronegative than carbon. This gives an oxidation number of 3 +1 -1 =3.
[Edited on 14-4-2007 by Pyrovus]
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Magpie
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Yes, Pyrovus, I see what you mean. Valence and oxidation state are not the same thing. This means that, in a general sense, giving a sign to a
valence is not appropriate.
The original question was for the "oxidation state" of N. I then must agree that it is +3 for R-NO2 and Ar-NO2.
[Edited on by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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