Examples of oxide in the following topics:
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- Transition metals typically form several oxidation states and therefore have several oxidation numbers.
- This oxidation number is an indicator of the degree of oxidation (loss of electrons) of an atom in a chemical compound.
- O2- and S2- have oxidation numbers of -2.
- In a molecule or compound, the oxidation number is the sum of the oxidation numbers of its constituent atoms.
- The oxidation number of H is +1 (H+ has an oxidation number of +1).
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- Metal oxides typically contain an anion of oxygen in the oxidation state of −2.
- Most of the Earth's crust consists of solid oxides, the result of elements being oxidized by the oxygen in air or water.
- Although most metal oxides are polymeric, some oxides are monomeric molecules.
- Those attacked only by acids are basic oxides; those attacked only by bases are acidic oxides.
- Metals tend to form basic oxides, non-metals tend to form acidic oxides, and amphoteric oxides are formed by elements near the boundary between metals and non-metals (metalloids).
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- The carbon atom of a carbonyl group has a relatively high oxidation state.
- Useful tests for aldehydes, Tollens' test, Benedict's test & Fehling's test, take advantage of this ease of oxidation by using Ag(+) and Cu(2+) as oxidizing agents (oxidants).
- The Fehling and Benedict tests use cupric cation as the oxidant.
- This deep blue reagent is reduced to cuprous oxide, which precipitates as a red to yellow solid.
- All these cation oxidations must be conducted under alkaline conditions.
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- A parallel and independent method of characterizing organic reactions is by oxidation-reduction terminology.
- 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.
- Carbon atoms colored blue are reduced, and those colored red are oxidized.
- Peracid epoxidation and addition of bromine oxidize both carbon atoms, so these are termed oxidation reactions.
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- An atom's increase in oxidation state through a chemical reaction is called oxidation, and it involves a loss of electrons; an decrease in an atom's oxidation state is called reduction, and it involves the gain of electrons.
- The oxidation state of a free element (uncombined element) is 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.
- This helps determine the oxidation state of any one element in a given molecule or ion, assuming that we know the common oxidation states of all of the other elements.
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- The most common oxidation states of the metal manganese are +2, +3, +4, +6, and +7; the +2 oxidation state is the most stable.
- Manganese compounds where manganese is in oxidation state of 7+ are powerful oxidizing agents.
- Compounds with oxidation states 5+ (blue) and 6+ (green) are strong oxidizing agents.
- The 3+ oxidation state is seen in compounds like manganese(III) acetate; these are very powerful oxidizing agents.
- Predict the oxidation or reduction propensity of a manganese species given its formula or oxidation state.
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- Phenols are rather easily oxidized despite the absence of a hydrogen atom on the hydroxyl bearing carbon.
- 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.
- One such oxidant is Fremy's salt, shown below.
- Although chromic acid oxidation of phenols having an unsubstituted para-position gives some p-quinone product, the reaction is complex and is not synthetically useful.
- The solvent of choice for these oxidations is usually methanol or dimethylformamide (DMF).
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- Chromium exhibits a wide range of possible oxidation states, where the +3 state is the most stable energetically.
- It is dehydrated by heating to form the green chromium(III) oxide (Cr2O3), which is the stable oxide with a crystal structure identical to that of corundum.
- Chromium(VI) compounds are powerful oxidants at low or neutral pH.
- Both the chromate and dichromate anions are strong oxidizing reagents at low pH.
- The oxidation state +5 is only realized in few compounds but are intermediates in many reactions involving oxidations by chromate.
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- Redox (reduction-oxidation) reactions are those in which the oxidation states of the reactants change.
- As usual, oxidation and reduction occur together.
- In H2O2, oxygen has an oxidation state of -1.
- In H2O, its oxidation state is -2, and it has been reduced.
- In O2 however, its oxidation state is 0, and it has been oxidized.
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- Six rules can be used when assigning oxidation numbers:
- In compounds with nonmetals, the oxidation number of hydrogen is +1.
- Oxygen is assigned an oxidation number of -2 in most compounds.
- In oxygen difluoride (OF2), the oxidation number of oxygen is +2, while in dioxygen difluoride (O2F2), oxygen is assigned an oxidation number of +1 because fluorine is the more electronegative element in these compounds, so it is assigned an oxidation number of -1.
- Apply the rules for assigning oxidation numbers to atoms in compounds