There are many reactions which occur in our daily life like rusting of iron, fading of color from the clothes, burning of combustible substances such as domestic use gas, wood, coal, etc. All such processes fall under the specific type of reaction called as oxidation – reduction reaction.
A large number of industrial processes like electroplating, extraction of metals like aluminum and sodium, bleaching of wood pulp, manufacture of caustic soda, etc., are also based on the redox reactions. Reduction – oxidation reactions also form the basis of electrochemical and electrolytic cells.
Carboxylic acids are reduced to primary alcohols on treatment with lithium aluminium hydride or better with diborane. Here -COOH group is reduced to -CH2OH
Sodium borohydride does not reduce the carboxyl group.
|Chemical Reaction Calculator||Redox Reaction Calculator|
According to the classical concept, reduction reaction is defined as the addition of hydrogen or removal of oxygen.
To depict the classical concept of reduction, let us look at the following example :
Cl2 + H2 → HCl
In the above reaction, Hydrogen is added to chlorine to form hydrogen chloride. Thus, chlorine gas is getting reduced to form hydrochloric acid.
H2S + Cl2 → 2HCl + S
Same as the first example, Hydrogen is added to chlorine by hydrogen sulfide, thereby reducing chlorine.
A substance which provides or supplies hydrogen or removes oxygen is said to be a reducing agent according to the classical concept. So, in the above example, since hydrogen sulfide is providing hydrogen to chlorine, Hydrogen sulfide is the ‘reducing agent’.
ZnO + C → Zn + CO
In the above reaction, carbon removes oxygen from zinc oxide, thereby reducing the zinc oxide.
This, carbon here is the reducing agent.
Fe2O3 + 3CO → 2Fe + 3CO2
Carbon monoxide acts as a reducing agent and takes away oxygen from Fe2O3.
With respect to the classical concept, oxidation involves addition of oxygen and removal of hydrogen. It is the complete opposite of reduction.
C + O2 → CO2
In the above reaction, Oxygen is added to carbon, thereby oxidizing it.
2Mg + O2 → 2MgO
Oxygen is added to magnesium to convert it into its oxide, thereby oxidizing it.
Example of an oxidation reaction proceeding with removal of hydrogen is,
H2S + Cl2 → 2HCl + S
Hydrogen is removed from sulfur. So, sulfur is getting oxidized.
An oxidizing agent is one, which supplies oxygen or removes hydrogen from another reactant.Since chlorine is removing hydrogen from hydrogen sulfide, chlorine is the oxidizing agent.
MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O
MnO2 supplies oxygen in the above example. So, manganese dioxide is an oxidizing agent.
|Chemistry Help||Chemistry Tutor|