Undergraduate
  1. General chemistry  1.1. Introduction to Chemistry  1.2. Atomic Structure  1.2.1. Subatomic particles  1.2.2. Atomic Model  1.2.3. Quantum numbers  1.2.4. Electron Configuration  1.2.5. Periodic trends  1.2.6. Isotopes and their applications  1.3. Chemical bond  1.3.1. Ionic bond  1.3.2. Covalent bonds  1.3.3. Metal Bond  1.3.4. Hybridization  1.3.5. Molecular geometry and VSEPR theory  1.3.6. Bond polarity and dipole moment  1.4. Stoichiometry  1.4.1. Mole concept  1.4.2. Empirical and molecular formula  1.4.3. Limiting reactant and excess reactant  1.4.4. Percent Yield and Purity  1.4.5. Dilution calculation  1.5. States of matter  1.5.1. Gas Laws  1.5.2. Matter and Intermolecular Forces  1.5.3. Solid and Crystal Structures  1.5.4. Phase diagram  1.5.5. Plasma and supercritical fluid  1.6. Chemical reactions  1.6.1. Types of Chemical Reactions  1.6.2. Balancing Chemical Equations  1.6.3. Thermochemical reactions  1.6.4. Reaction energy profiles  1.7. Solutions and Mixtures  1.7.1. Concentration units  1.7.2. Syndrome properties  1.7.3. Solubility and Solubility Rules  1.7.4. Henry's Law and Raoult's Law  1.7.5. Partition coefficient  1.8. Chemical equilibrium  1.8.1. Law of mass action  1.8.2. Le Chatelier's principle  1.8.3. Reaction quotient  1.8.4. To use this online calculator for Equilibrium Constant, enter Equilibrium Constant (Eq.) and hit the calculate button. Here is how the Equilibrium Constant calculation can be explained with given input values -> 0.05 = 0.05/0.  1.8.5. Acid-base balance  1.9. Acids and bases  1.9.1. Arrhenius, Brønsted–Lowry, and Lewis definitions  1.9.2. pH and pOH  1.9.3. Acid-base titration  1.9.4. Buffer Solution  1.9.5. Acid-base indicator  1.9.6. Polyprotic Acids and Bases  1.10. Electrochemistry  1.10.1. redox reactions  1.10.2. Galvanic and Electrolytic Cells  1.10.3. Nernst equation  1.10.4. Electrolysis  1.10.5. Faraday's laws of electrolysis  1.11. Thermodynamics  1.11.1. Laws of Thermodynamics  1.11.2. Enthalpy, entropy and Gibbs free energy  1.11.3. Spontaneity of reactions  1.11.4. Thermodynamic cycles (Hess's law, Carnot cycle)  1.12. Kinetics  1.12.1. Rate law and reaction order  1.12.2. Activation Energy and Catalyst  1.12.3. Collision theory  1.12.4. Reaction mechanism  1.12.5. Transition state theory
  2. Organic chemistry  2.1. Structure and relationships  2.1.1. Hybridisation in Carbon Compounds  2.1.2. Resonance and aromatization  2.1.3. Molecular orbitals  2.1.4. Inductive and mesomeric effects  2.2. Hydrocarbons  2.2.1. Hydrocarbons  2.2.2. Alkene  2.2.3. Alkynes  2.2.4. Aromatic compounds  2.2.5. Cycloalkanes and Conformation  2.3. Functional Group  2.3.1. Alcohols and phenols  2.3.2. Ethers and epoxides  2.3.3. Aldehyde and ketone  2.3.4. Carboxylic acids and derivatives  2.3.5. Amin  2.3.6. Esters and amides  2.3.7. Thiols and sulfides  2.4. Stereoscopic  2.4.1. Isomerism in Stereochemistry  2.4.2. Chirality and optical activity  2.4.3. Structural analysis  2.4.4. Diastereomers and Enantiomers  2.5.1. Substitution reactions  2.5.2. Elimination reactions  2.5.3. Addition reactions  2.5.4. Radical reactions  2.5.5. Rearrangement reactions  2.5.6. Pericyclic Reactions  2.6. Spectroscopy and structural analysis  2.6.1. Infrared Spectroscopy  2.6.2. Nuclear magnetic resonance spectroscopy  2.6.3. Mass Spectrometry  2.6.4. UV-visible spectroscopy  2.6.5. X-ray crystallography  2.7. Polymer chemistry  2.7.1. Addition and Condensation Polymers  2.7.2. Polymerization mechanism  2.7.3. Biodegradable Polymer  2.7.4. Conducting and smart polymers
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Ligands and coordination compounds  3.1.2. Crystal field theory  3.1.3. Molecular Orbital Theory in Coordination Compounds  3.1.4. Jahn–Taylor distortion  3.2. Main Group Chemistry  3.2.1. Alkali and alkaline earth metals  3.2.2. Halogens and Noble Gases  3.2.3. Transition metals and their complexes  3.2.4. Lanthanides and Actinides  3.3. Solid state chemistry  3.3.1. Crystal lattices and unit cells  3.3.2. Defects in solids  3.3.3. Electrical and magnetic properties  3.3.4. Superconductivity  3.4. Bio-inorganic chemistry  3.4.1. Metal ions in biology  3.4.2. Enzymatic reactions with metals  3.4.3. Metal poisoning and detoxification  3.4.4. Metalloproteins and Metalloenzymes
  4. Physical chemistry  4.1. Quantum Chemistry  4.1.1. Wave–particle duality  4.1.2. Schrödinger Equation  4.1.3. Quantum Numbers and Orbitals  4.1.4. Atomic and molecular spectroscopy  4.2. Statistical mechanics  4.2.1. Maxwell–Boltzmann distribution  4.2.2. Partitioning functions  4.2.3. Bose–Einstein and Fermi–Dirac statistics  4.3. Chemical thermodynamics  4.3.1. Gibbs Free Energy  4.3.2. Phase transition  4.3.3. Thermodynamic efficiency  4.4. Surface chemistry  4.4.1. Absorption and Catalysis  4.4.2. Colloids and Emulsions
  5. Analytical Chemistry  5.1. Classical methods  5.1.1. Gravimetric Analysis  5.1.2. titrimeter  5.2. Instrumental methods  5.2.1. Chromatography  5.2.2. Spectroscopy  5.2.3. Electroanalytical methods  5.2.4. X-ray diffraction
  6. Industrial Chemistry  6.1. Petrochemistry  6.2. Chemical engineering principles  6.3. Green Chemistry  6.4. Pharmaceuticals and Drug Synthesis
  7. Biochemistry  7.1. Carbohydrates  7.2. Proteins and enzymes  7.3. Lipids and membranes  7.4. Nucleic acids  7.5. Metabolism and Bioenergetics  7.6. Enzyme kinetics and mechanism

Undergraduate → Organic chemistry → Structure and relationships ↓


Inductive and mesomeric effects


Understanding inductive and mesomeric effects is important in explaining various phenomena in organic chemistry, including the reactivity, stability, acidity, and basicity of molecules. These effects are essentially types of electronic effects that are caused by the distribution of electronic charge within molecules.

Inductive effect

Inductive effect refers to the transmission of charge through a chain of atoms in a molecule by electrostatic induction. It occurs due to the difference in electronegativities between atoms. When an atom or group of atoms is more electronegative, it attracts electron density towards itself, leaving a partial positive charge on the surrounding atoms.

Types of inductive effects

  • -I effect: It occurs when an atom or group of atoms withdraws electrons. For example, halogens such as fluorine and chlorine exhibit -I effect because they pull electron density away from carbon atoms. The order of -I effect of some common substituents is: F > Cl > Br > I > OH > NR 3 + > NH 3 +.
  • +I effect: This occurs when an atom or group of atoms donates electrons. Alkyl groups are known to exhibit +I effect as they push electron density towards more electronegative atoms or groups. The order of +I effect for some common groups is: -CH(CH 3 ) 2 > -CH 2 CH 3 > -CH 3.
Electronegative group (-I effect) Alkyl group (+I effect) C C C R

Effects of inductive influence

The inductive effect affects many physical and chemical properties of organic compounds:

  • Acidity and basicity: The presence of electron-withdrawing groups increases the acidity of molecules by stabilizing the negative charge on the conjugate bases. For example, in benzoic acids, a nitro group at the meta position will increase the acidity due to its -I effect.
  • Reactivity: In nucleophilic substitution reactions, –I groups can stabilize the transition state, thus lowering the reaction barrier and accelerating the reaction.

Mesomeric effect

The mesomeric effect is a type of resonance effect by which electron pairs, usually from p orbitals, are delocalized to multiple atoms in a molecule. It plays an important role in conjugated systems.

Types of mesomeric effect

  • +M effect: It arises when electron-donating groups (such as -OH or -NH 2 ) donate electrons through resonance. This leads to higher electron density on some atoms. Amino and methoxy groups are examples of electron-donating groups through the +M effect.
  • -M effect: This occurs when electron-withdrawing groups, such as carbonyl or nitro groups, pull electrons toward themselves through resonance. Such groups reduce electron density on certain atoms and contribute to deshielding in NMR or make the molecule more reactive toward nucleophiles.
            +M effect example:
            CH 2 =CH-CH=CH 2 + OH ↔ CH 2 -CH=CH-CH 2 -OH
        CH 2 =CH-CH=CH 2 + OH ↔ CH 2 -CH=CH-CH 2 -OH
        
            -m effect example:
            CH 2 =CH-CH=CH 2 + NO 2 ↔ CH 2 -CH=CH-NO 2
        CH 2 =CH-CH=CH 2 + NO 2 ↔ CH 2 -CH=CH-NO 2

Effects of the mesomeric effect

  • Aromaticity: The mesomeric effect is a key concept in explaining the stability of aromatic compounds. For example, benzene is an ideal case where the -M effect of the double bonds spreads over several atoms to form a resonance hybrid.
  • Stability of carbocations and carbanions: Mesomeric effect stabilizes carbocations by displacing the positive charge and stabilizes carbanions by dispersing the negative charge.
benzene ring Resonance arrow

Conclusion

Inductive and mesomeric effects are essential for predicting and understanding the behavior of organic molecules. They are fundamental for determining the reactivity, stability, and structural properties of organic compounds. A solid understanding of these concepts helps to rationalize the mechanisms of organic reactions and design molecules with desired properties.

In conclusion, both inductive and mesomeric effects play a vital role in shaping the behavior and characteristics of organic molecules. Mastering these concepts is important for anyone seeking a deeper understanding of organic chemical reactions and structures. Revisit this explanation, practice with the structures, and apply these concepts to strengthen your understanding.


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Inductive and mesomeric effects

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