PHD
  1. Inorganic chemistry  1.1. Coordination chemistry  1.1.1. Ligand field theory  1.1.2. Crystal field theory  1.1.3. Molecular Orbital Theory for Coordination Compounds  1.1.4. Stability of Coordination Compounds  1.1.5. Electronic spectra of coordination compounds  1.1.6. Isomerism in Coordination Compounds  1.1.7. Kinetics and mechanism of coordination reactions  1.2. Organometallic Chemistry  1.2.1. Metal Carbonyls  1.2.2. Metal alkyl and aryl  1.2.3. Fischer and Schrock carbonaceans  1.2.4. Oxidative Addition and Reductive Elimination  1.2.5. Metal Hydrides  1.2.6. Catalysis by organometallic compounds  1.2.7. Metallocenes and Sandwich Complexes  1.2.8. CH activation  1.3. Solid state chemistry  1.3.1. Crystal structures and lattices  1.3.2. Band theory and electrical properties  1.3.3. Defects in the crystal  1.3.4. Synthesis of solid state materials  1.3.5. Magnetic and optical properties of solids  1.3.6. Superconductivity  1.3.7. Solid state ionics  1.4. Bio-inorganic chemistry  1.4.1. Metalloproteins and enzymes  1.4.2. Metal ion transport and storage  1.4.3. The role of metals in medicine  1.4.4. Bioinspired catalysis  1.4.5. Metal–DNA interactions  1.4.6. Metal Complexes in Medical Science  1.5. Lanthanides and Actinides  1.5.1. Electronic configuration and oxidation states in lanthanides and actinides  1.5.2. Spectral and Magnetic Properties in Lanthanides and Actinides  1.5.3. Separation and Extraction of Lanthanides and Actinides  1.5.4. Coordination chemistry of f-block elements  1.6. Main Group Chemistry  1.6.1. Chemistry of boron compounds  1.6.2. Chemistry of Silicon and Germanium Compounds  1.6.3. Chemistry of Phosphorus and Sulfur Compounds  1.6.4. Organosilicon chemistry  1.6.5. Noble Gas Chemistry
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition and substitution reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic Reactions  2.1.7. Photochemical reactions  2.2. Stereoscopic  2.2.1. Chirality and optical activity  2.2.2. Structural analysis  2.2.3. Stereoelectronic effects  2.2.4. Asymmetric synthesis  2.2.5. Dynamic Stereochemistry  2.3. Organometallic Chemistry in Organic Synthesis  2.3.1. Organolithium and organomagnesium reagents  2.3.2. Transition metal catalyzed coupling reactions  2.3.3. Palladium-catalyzed reactions  2.3.4. Olefin Metathesis  2.3.5. Gold and silver catalysis  2.4. Natural products chemistry  2.4.1. Alkaloids and terpenoids  2.4.2. Steroids and Flavonoids  2.4.3. Total synthesis of natural products  2.4.4. Biosynthesis of natural products  2.5. Supramolecular Chemistry  2.5.1. Host-Guest Chemistry  2.5.2. Self-assembly and molecular recognition  2.5.3. Supramolecular Catalysis  2.5.4. Molecular Machines
  3. Physical Chemistry  3.1. Thermodynamics  3.1.1. Laws of Thermodynamics  3.1.2. Chemical Potential and Equilibrium  3.1.3. Statistical thermodynamics  3.1.4. Non-equilibrium thermodynamics  3.2. Quantum Chemistry  3.2.1. Schrödinger equation and its applications  3.2.2. Molecular orbital theory  3.2.3. Density functional theory  3.2.4. Post-Hartree–Fock methods  3.3. Chemical kinetics  3.3.1. Reaction rate theory  3.3.2. Mechanism and rate laws  3.3.3. Catalysis and enzyme kinetics  3.3.4. Reaction dynamics  3.4. Spectroscopy and molecular structure  3.4.1. Infrared Spectroscopy  3.4.2. UV-visible spectroscopy  3.4.3. Nuclear Magnetic Resonance Spectroscopy  3.4.4. Mass Spectrometry  3.4.5. Raman Spectroscopy  3.5. Surface and Colloid Chemistry  3.5.1. Absorption and Catalysis  3.5.2. Surfactants and micelles  3.5.3. Colloidal Stability  3.5.4. Nanomaterials and Interfaces
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.1.4. Ion Chromatography  4.2. Electroanalytical techniques  4.2.1. Voltammetry and Polarography  4.2.2. Conductometry and potentiometry  4.2.3. Colometry  4.3. Spectroscopic Methods  4.3.1. Atomic absorption spectroscopy  4.3.2. Fluorescence Spectroscopy  4.3.3. X-ray diffraction  4.3.4. Electron paramagnetic resonance spectroscopy  4.4. Chemometrics  4.4.1. Data processing and statistical methods  4.4.2. Multidisciplinary analysis  4.4.3. Machine Learning in Analytical Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.2. Quantum chemistry methods  5.3. Computational drug design  5.4. Machine Learning in Chemistry  5.5. Ab initio molecular dynamics
  6. Biophysics and Medicinal Chemistry  6.1. Drug discovery and design  6.2. Enzyme kinetics and inhibition  6.3. Chemical biology approach  6.4. Protein-ligand interactions  6.5. Bioorthogonal chemistry
  7. Materials chemistry  7.1. Polymer chemistry  7.1.1. Polymerization mechanism  7.1.2. Functional Polymers  7.1.3. Biodegradable Polymer  7.1.4. Conducting and semiconducting polymers  7.2. Nano Chemistry  7.2.1. Nanoparticles and nanostructures  7.2.2. Carbon-based nanomaterials  7.2.3. Quantum dots  7.3. Energy and Environmental Chemistry  7.3.1. Battery and Fuel Cell Chemistry  7.3.2. Green chemistry and sustainable materials  7.3.3. Photocatalysis

PHD → Organic chemistry → Reaction mechanism ↓


Radical reactions


Introduction

Radical reactions play an important role in organic chemistry, being responsible for many processes in both synthetic and biological systems. These reactions involve radicals, which are highly reactive species with unpaired electrons and can lead to the formation of new bonds or the breaking of old bonds.

Understanding radicals

A radical is a molecule, atom, or ion that has an unpaired valence electron. Because of this unpaired electron, radicals are usually very reactive, trying to pair the lone electron with another to reach a more stable state.

Formation of radicals

Radicals can be generated in several ways, most commonly by thermal, photochemical, or chemical means.

Thermal methods

In thermal methods, heat causes homolytic cleavage, where the bond between two atoms is broken equally, and each atom retains one electron from the bond:

r−r' → r˙ + r'˙

Photochemical methods

Photochemical methods involve the absorption of light. When a molecule absorbs light, it may become excited, and the bonds may undergo homolytic cleavage:

R−R' → R˙ + R'˙ (on hv)

hv represents the energy of the light used.

Chemical methods

Some compounds, such as peroxides and organic halides, can react or decompose to form radicals. For example:

(ROOR) → 2RO˙

Propagation of radical reactions

Once initiated, radical reactions proceed through a series of propagation steps. These involve the formation of new radicals by reacting radicals with stable molecules:

r˙ + r'h → rh + r'˙

This is a basic example of a propagation step where a radical abstracts a hydrogen atom from a stable molecule.

Example of radical bromination

CH4 + Br2 → CH3Br + HBr Initiation: 2Br2 → 2Br˙ Spread: Br˙ + CH4 → CH3˙ + HBr CH3˙ + Br2 → CH3Br + Br˙

Termination phase

Radical reactions eventually terminate when two radicals combine to form a stable product, reducing the number of radicals:

r˙ + r'˙ → r−r'

This situation stops the radical chain reaction because the radicals are destroyed without producing new radicals.

Basic reactions in biological systems

Radical reactions are found in nature. For example, in biological systems, radicals are involved in processes such as the formation of biopolymers and DNA synthesis.

Factors affecting radical stability

The stability of radicals is important in determining the pathways and products of radical reactions. Factors such as hybridization, resonance, and the presence of electron-withdrawing or donating groups affect radical stability:

Echo

Resonance-stabilized radicals are more stable because the unpaired electrons are displaced on more than one atom.

Hybridization

sp 2 -hybridized carbon radicals are generally more stable than sp 3 -hybrid carbon radicals because they have greater s-character and lower p-orbital energy.

Applications of radical reactions

Radical reactions are used in many synthetic processes, such as polymerization, halogenation, and oxidative processes.

Polymerization

The process of building larger molecules (polymers) from smaller molecules (monomers) often involves radical mechanisms.

n (CH2=CH2) → [−CH2−CH2−]n (using radicals)

Halogenation

Radical halogenation is a radical reaction used to incorporate halogens into organic molecules.

RH + X2 → RX + HX

Conclusion

Radical reactions are a fundamental aspect of organic chemistry, providing pathways for building complex molecules. By understanding the nature, origin, and behavior of radicals, chemists can manipulate these reactions for a variety of applications ranging from synthetic chemistry to biological systems.


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Rearrangement reactions
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Radical reactions

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