Using electrical energy to drive reduction reactions.

Description: The introduction of one or more nitro groups ($-NO_2$) into an organic molecule, typically replacing a hydrogen atom on an aromatic ring or reacting with an alcohol to form a nitrate ester.
Applications:
- Explosives: Synthesis of high explosives like Trinitrotoluene (TNT), nitroglycerin, and RDX.
- Dyes & Pigments: Production of nitro-compounds as intermediates for various dyes.
- Pharmaceuticals: Used in the synthesis of certain drugs.
- Chemical Intermediates: Manufacturing of nitrobenzene (a precursor for aniline, which is used for polyurethanes), nitrophenols, and other fine chemicals.
Common Reagents: Usually a "nitrating mixture" consisting of concentrated nitric acid ($HNO_3$) and concentrated sulfuric acid ($H_2SO_4$). Sulfuric acid acts as a catalyst, protonating nitric acid to form the nitronium ion ($NO_2^+$), which is the active nitrating species.
Reaction Conditions: Temperature control is critical to avoid side reactions and ensure selectivity, especially for poly-nitration.

Description: A chemical reaction that involves the introduction of one or more halogen atoms (fluorine, chlorine, bromine, or iodine) into an organic compound, typically replacing hydrogen atoms or adding across double/triple bonds.
Applications:
- Polymers: Production of vinyl chloride (monomer for PVC), chlorofluorocarbons (CFCs, historically used as refrigerants and propellants), and fluoropolymers (e.g., Teflon).
- Pesticides & Herbicides: Many agrochemicals contain halogen atoms for biological activity.
- Pharmaceuticals: Halogens are often incorporated into drug molecules to modify their properties and activity.
- Solvents: Production of chlorinated solvents like chloroform or trichloroethylene.
- Chemical Intermediates: Halogenated compounds serve as versatile building blocks in organic synthesis.
Types & Mechanisms:
- Chlorination, Bromination, Iodination, Fluorination: Specific halogen used.
- Free Radical Halogenation: Typically for alkanes, initiated by light or heat.
- Electrophilic Aromatic Halogenation: For aromatic compounds, often catalyzed by Lewis acids (e.g., $FeCl_3$ for chlorination).
- Addition Halogenation: Across double or triple bonds (e.g., bromination of alkenes).

Description: The introduction of a sulfonic acid group ($-SO_3H$) into an organic molecule, usually by replacing a hydrogen atom on an aromatic ring or by adding to an alkene.
Applications:
- Detergents & Surfactants: Key process for producing alkylbenzene sulfonates, which are major components of synthetic detergents due to their amphiphilic nature.
- Dyes & Pigments: Sulfonic acid groups increase water solubility, important for textile dyes.
- Pharmaceuticals: Used in the synthesis of sulfa drugs.
- Ion-Exchange Resins: Polymeric materials with sulfonic acid groups are used in water softening and purification.
- Tanning Agents: For leather treatment.
Common Reagents:
- Concentrated sulfuric acid ($H_2SO_4$).
- Oleum (fuming sulfuric acid, $H_2SO_4 \cdot nSO_3$).
- Chlorosulfonic a