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 → Stereoscopic ↓


Diastereomers and Enantiomers


Stereochemistry is a fascinating subfield of chemistry that deals with the spatial arrangement of atoms in molecules. Two important concepts within stereochemistry are diastereomers and enantiomers. These terms refer to different types of stereoisomers, which are molecules with the same molecular formula and sequence of bonded atoms (structure), but which differ in the three-dimensional orientation of their atoms in space.

Stereoisomerism

Before learning about diastereomers and enantiomers, it is important to understand stereoisomerism. Stereoisomers include both diastereomers and enantiomers, and they arise when a molecule has chiral centers or other types of stereocenters, such as double bonds with geometric isomerism.

Imagine a simple compound that has a chiral center, such as lactic acid. Its molecular formula is C 3 H 6 O 3, and the structural formula can be written as: 
          HO(CH3)COOH

To right

A molecule is said to be chiral if it cannot be superimposed on its mirror image. Chirality arises from the presence of a chiral center, usually a carbon atom with four different groups attached to it. Consider a simple chiral molecule, 2-butanol:

    CH3-CH(OH)-CH2-CH3

The second carbon (the one with the OH group) is the chiral center because it is bonded to four different groups: a methyl group (CH 3), an ethyl group (CH 2 -CH 3), a hydroxyl group (OH), and a hydrogen atom (H).

Enantiomers

Enantiomers are a type of stereoisomers that are non-superimposable mirror images of each other. Their physical properties are identical, except for the direction in which they rotate plane-polarized light and their responses in chiral environments.

For example, the two enantiomers of 2-butanol are (R)-2-butanol and (S)-2-butanol. The "R" and "S" designations come from the Cahn-Ingold-Prelog priority rules, a standard method for assigning absolute configurations at chiral centers.

Oh CH 3 CH 2 CH 3 Oh CH 3 CH 2 CH 3

Illustration of (R)-2-butanol and its enantiomer (S)-2-butanol.

Diastereomers

Diastereomers, unlike enantiomers, are not mirror images of each other and have different physical and chemical properties. They arise in compounds with two or more chiral centers. Importantly, not all stereoisomers with two or more chiral centers are diastereomers; only those that are not mirror images are diastereomers.

Consider the compound tartaric acid, which has the molecular formula C 4 H 6 O 6; it contains two chiral centers:

      hook-choh-choh-kooh

Tartaric acid can exist as a pair of enantiomers (D-tartaric acid and L-tartaric acid), but there is also a third stereoisomer called meso-tartaric acid, which is a diastereomer of the other two. Meso-tartaric acid has an internal plane of symmetry, making it achiral.

Example of diastereomers

Let us consider another example involving 2,3-butanediol, which has the molecular formula C 4 H 10 O 2.

          CH 3 -CHOH-CHOH-CH 3

This molecule can exist in three different stereoisomeric forms:

  • (2R,3R)-2,3-butanediol
  • (2S, 3S)-2,3-butanediol
  • (2R,3S)-2,3-butanediol (meso form, achiral)
Oh Oh H CH 3 Oh H Oh CH 3

Illustration of the enantiomers and diastereomers of 2,3-butanediol.

Physical and chemical properties

Enantiomers have similar physical properties, such as boiling point, melting point, and solubility, but they differ in optical activity. They rotate plane-polarized light in opposite directions. For example, if one enantiomer rotates light clockwise (dextrorotatory), the other will rotate it counterclockwise (levorotatory) by the same magnitude. When it comes to chemical reactivity, enantiomers can behave differently in chiral environments such as biological systems.

In contrast, diastereomers usually have different physical and chemical properties. This is because their different spatial arrangements lead to variations in intermolecular interactions, which can affect their boiling and melting points, solubility, and reactivity.

Importance of stereochemistry

Stereochemistry, particularly the study of enantiomers and diastereomers, is important in many areas of chemistry, biology, and pharmacology. In pharmaceuticals, different interactions of drug enantiomers with biological systems can lead to different therapeutic outcomes or side effects. For example, one enantiomer of a drug may be therapeutic, while another may be inactive or even harmful.

Understanding diastereomers is also essential in the synthesis of complex molecules, where control over stereochemistry is essential to obtain desired properties of the final product.

Conclusion

Diastereomers and enantiomers represent important concepts in stereochemistry and play a vital role in chemical reactions and product outcomes. Their study helps us understand the complexities of molecular interactions and the importance of spatial arrangement in chemistry.


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Diastereomers and Enantiomers

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