[Chemistry Class Notes] on Oxidation and Reduction Reactions Pdf for Exam

An oxidation reduction reaction is a type of chemical reaction that constitutes a transfer of electrons within two elements. It is a type of chemical reaction that involves the change in the oxidation number of an ion, atom, or molecule by the loss or gain of an electron. Redox reactions form the core of the sustenance of life on earth, supporting some of the most crucial chemical reactions such as photosynthesis, respiration, corrosion, and combustion. Oxidation and reduction (redox) reactions are important because they ignite the natural or biological plus artificial energy sources on this planet. The oxidation of molecules releases typically large amounts of energy by removing hydrogen and replacing it with oxygen.

Oxidation Reaction

Oxidation is the lack of electrons during a reaction by an atom, molecule, or ion. Oxidation happens when the oxidation state of an atom, molecule, or ion is enhanced. The opposite method is called reduction, which results when there is a gain of electrons. According to the modern definition, the reaction in which oxygen is included is still oxidation. Therefore oxidation can be defined as the loss of a hydrogen atom, while the gain of a hydrogen atom is termed as reduction. An example of oxidation reaction can be the transformation of ethanol to ethanal: CH₃CH₂OH → CH₃CHO

Ethanol is regarded as oxidised because it loses hydrogen. By converting the equation, ethanal can be lessened by adding hydrogen to it to form ethanol. 

Reduction 

Reduction is a chemical reaction that includes the electrons gained by one of the atoms required in the reaction between two chemicals. It refers to the electron-accepting element since the electron-accepting element’s oxidation state is lowered by gaining an electron. An example of a reduction is when iron reacts with oxygen, forming iron oxides, also known as rust. This is called a redox reaction. By employing carbon monoxide, a blast furnace can reverse the reaction, as it can serve as the reducing agent for the iron.

Redox Reaction Definition

Redox definition is a kind of chemical reaction in which the atom’s oxidation states are altered. Redox reactions are depicted by the formal exchange of electrons among different species of chemicals, where one species experiences electron loss (oxidation) (reducing agent) and the other electron species experiences electron gain (reduction) (oxidising agent). The term “redox” comes from two ideas associated with electron transfer: reduction and oxidation. There are also five types of redox reactions: combination, decomposition, displacement, combustion, and disproportion. 

Redox reactions can happen comparatively slowly, as in the formation of rust, or much more quickly, as in the case of burning fuel. There are simple redox methods, such as the oxidation of carbon to produce carbon dioxide (CO₂) or the conversion of carbon by hydrogen to produce methane (CH₄), and more complicated processes such as the oxidation of glucose (C₆H₁₂O₆) in the human body. The investigation of bond energies and ionisation energies in water allows the calculation of the redox potentials. 

Aldehyde

Aldehydes are a group of organic compounds in which a carbon atom combines a single bond with a hydrogen atom, a double bond with an oxygen atom, and a single bond with a different atom or group of atoms. The double bond within carbon and oxygen is characteristic of all aldehydes, known as the carbonyl group. Many aldehydes have pleasing odours, and in law, they are procured from alcohols by dehydrogenation, from which process came the name aldehyde. 

Aldehydes can be subdued to primary alcohols (RCHO → RCH₂OH) with many reducing agents; the most commonly used are lithium aluminium hydride (LiAlH₄), hydrogen (H₂) or sodium borohydride (NaBH₄) with the help of transition catalysts such as Ni (nickel), Pd(palladium), Pt (platinum), or Rh (rhodium). 

Oxidation of Aldehydes

There is a wide variety of reagents that can induce the oxidation of aldehydes to carboxylic acids. The most common reagent for this change is CrO₃ in aqueous acid, also termed as Jones Reagent. Oxidation reactions of aldehydes are less relevant than reductions. Alcohols may be oxidised to yield aldehydes, ketones, and carboxylic acids. The oxidation of organic compounds usually extends the number of bonds from carbon to oxygen, and it may reduce the number of bonds to hydrogen.