Oxidation State

(noun)

The state of an atom having a particular oxidation number.

Related Terms

Examples of Oxidation State in the following topics:

  • Oxidation States of Phosphorus Compounds

    • The difference in oxidation states between nitrogen and phosphorus is less pronounced than between oxygen and sulfur.
    • Organophosphorus compounds having phosphorus oxidation states ranging from –3 to +5, as shown in the following table, are well known (some simple inorganic compounds are displayed in green).

  • Oxidation States

    • Oxidation state is the hypothetical charge of an atom if all of its bonds to other atoms were completely ionic.
    • Oxidation state indicates the degree of oxidation for an atom in a chemical compound; it is the hypothetical charge that an atom would have if all bonds to atoms of different elements were completely ionic.
    • Oxidation states are typically represented by integers, which can be positive, negative, or zero.
    • For example, Cl- has an oxidation state of -1.
    • When present in most compounds, hydrogen has an oxidation state of +1 and oxygen an oxidation state of −2.

  • Oxidation States of Sulfur Compounds

    • Oxygen assumes only two oxidation states in its organic compounds (–1 in peroxides and –2 in other compounds).
    • Sulfur, on the other hand, is found in oxidation states ranging from –2 to +6, as shown in the following table (some simple inorganic compounds are displayed in orange).
    • If you restrict your formulas to valence shell electron octets, most of the higher oxidation states will have formal charge separation, as in equation 2 above.
    • Oxidation of 1º and 2º-alcohols to aldehydes and ketones changes the oxidation state of carbon but not oxygen.
    • Oxidation of thiols and other sulfur compounds changes the oxidation state of sulfur rather than carbon.

  • Manganese

    • The most common oxidation states of the metal manganese are +2, +3, +4, +6, and +7; the +2 oxidation state is the most stable.
    • The most common oxidation states of manganese are 2+, 3+, 4+, 6+, and 7+.
    • Compounds with oxidation states 5+ (blue) and 6+ (green) are strong oxidizing agents.
    • The 2+ oxidation state is the state used in living organisms for essential functions; other states are toxic for the human body.
    • Permanganate (7+ oxidation state) compounds are purple and can give glass a violet color.

  • Oxidation Numbers of Metals in Coordination Compounds

    • Transition metals typically form several oxidation states and therefore have several oxidation numbers.
    • Oxidation number are typically represented by small integers.
    • Unfortunately, there is no simple rule to determining oxidation state possibilities among the transition metals, so it is best simply to memorize the common states of each element.
    • The "common" oxidation states of these elements typically differ by two.
    • Calculate the oxidation state of a metal in a coordination compound.

  • Balancing Redox Equations

    • Redox (oxidation-reduction) reactions include all chemical reactions in which atoms have their oxidation states changed.
    • Oxidation is the loss of electrons—or the increase in oxidation state—by a molecule, atom, or ion.
    • Reduction is the gain of electrons—or the decrease in oxidation state—by a molecule, atom, or ion.
    • Oxidation: $Mn^{2+} \rightarrow MnO_4^-$ (Mn goes from a +2 to a +5)
    • Oxidation: 2 OH− + SO32− → SO42− + H2O + 2 e−

  • Oxidation

    • The carbon atom of a carbonyl group has a relatively high oxidation state.
    • This is reflected in the fact that most of the reactions described thus far either cause no change in the oxidation state (e.g. acetal and imine formation) or effect a reduction (e.g. organometallic additions and deoxygenations).

  • Reductions & Oxidations of Carboxylic Acids

    • The carbon atom of a carboxyl group is in a relatively high oxidation state.
    • Because it is already in a high oxidation state, further oxidation removes the carboxyl carbon as carbon dioxide.
    • Depending on the reaction conditions, the oxidation state of the remaining organic structure may be higher, lower or unchanged.
    • The second reaction is an interesting bis-decarboxylation, in which the atoms of the organic residue retain their original oxidation states.
    • Finally, the third example illustrates the general decarboxylation of β-keto acids, which leaves the organic residue in a reduced state (note that the CO2 carbon has increased its oxidation state. ).

  • Oxidation of Phenols

    • The redox equilibria between the dihydroxybenzenes hydroquinone and catechol and their quinone oxidation states are so facile that milder oxidants than chromate (Jones reagent) are generally preferred.

  • Oxidations & Reductions

    • Carbon atoms may have any oxidation state from –4 (e.g.
    • Fortunately, we need not determine the absolute oxidation state of each carbon atom in a molecule, but only the change in oxidation state of those carbons involved in a chemical transformation.
    • If the number of hydrogen atoms bonded to a carbon increases, and/or if the number of bonds to more electronegative atoms decreases, the carbon in question has been reduced (i.e. it is in a lower oxidation state).
    • If there has been no change in the number of such bonds, then the carbon in question has not changed its oxidation state.
    • In the hydrolysis reaction of a nitrile shown above, the blue colored carbon has not changed its oxidation state.