Graduate
  1. Physical Chemistry  1.1. Thermodynamics  1.1.1. Laws of Thermodynamics  1.1.2. Enthalpy and heat capacity  1.1.3. Entropy and free energy  1.1.4. Phase Equilibrium  1.1.5. Statistical thermodynamics  1.1.6. Thermodynamic cycle  1.1.7. Fugacity and activity  1.2. Quantum Chemistry  1.2.1. Principles of quantum mechanics  1.2.2. Schrödinger Equation  1.2.3. Particle in a box  1.2.4. Operators and eigenvalues  1.2.5. Atomic orbitals  1.2.6. Molecular orbital theory  1.2.7. Perturbation theory  1.2.8. Valence bond theory  1.2.9. Hybridization and chemical bonding  1.3. Chemical kinetics  1.3.1. Rate laws and reaction mechanisms  1.3.2. Collision theory  1.3.3. Transition state theory  1.3.4. Enzyme Kinetics  1.3.5. Chain Reactions and Polymerization  1.3.6. Photochemical reactions  1.4. Statistical mechanics  1.4.1. Partitioning functions  1.4.2. Molecular distribution functions  1.4.3. Boltzmann Distribution  1.4.4. Bose–Einstein and Fermi–Dirac statistics  1.5. Spectroscopy  1.5.1. Rotational Spectroscopy  1.5.2. Vibrational Spectroscopy  1.5.3. Electronic Spectroscopy  1.5.4. Nuclear magnetic resonance spectroscopy  1.5.5. Mass Spectrometry  1.5.6. Raman Spectroscopy  1.5.7. Electron paramagnetic resonance spectroscopy  1.6. Surface and colloidal chemistry  1.6.1. Absorption isotherm  1.6.2. Surface tension and wetting  1.6.3. Colloidal Stability  1.6.4. Catalysis  1.6.5. Emulsions and micelles  1.7. Electrochemistry  1.7.1. Nernst equation  1.7.2. Electrochemical cells  1.7.3. Conductivity and mobility  1.7.4. War  1.7.5. Fuel cells  1.7.6. Electrolysis
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic reactions  2.2. Spectroscopy and structural determination  2.2.1. UV-Vis Spectroscopy  2.2.2. IR Spectroscopy  2.2.3. NMR Spectroscopy  2.2.4. Mass Spectrometry  2.2.5. X-ray crystallography  2.3. Stereoscopic  2.3.1. Chirality and optical activity  2.3.2. Structural analysis  2.3.3. Geometrical isomerism  2.3.4. Dynamic Stereochemistry  2.4. Organometallic Chemistry  2.4.1. Organolithium and organomagnesium reagents  2.4.2. Palladium-catalyzed cross-coupling reactions  2.4.3. Transition Metal Complexes  2.4.4. Metal–carbon bond  2.5. Polymer chemistry  2.5.1. Polymerization mechanism  2.5.2. Polymer Characteristics  2.5.3. Biodegradable Polymer  2.5.4. Conducting polymer  2.5.5. Supramolecular polymers  2.6. Medicinal chemistry  2.6.1. Drug design and development  2.6.2. Pharmacokinetics and pharmacodynamics  2.6.3. Structure-activity relationships  2.6.4. Molecular docking and drug screening
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Crystal field theory  3.1.2. Ligand field theory  3.1.3. Spectrochemical Series  3.1.4. Chelation and stability  3.2. Organometallic Chemistry  3.2.1. Metal Carbonyls  3.2.2. Catalysis by organometallic complexes  3.2.3. Metallocenes  3.3. Bio-inorganic chemistry  3.3.1. Metalloproteins and enzymes  3.3.2. The role of metals in biological systems  3.3.3. Metal ion transport and storage  3.4. Solid state chemistry  3.4.1. Crystal Structures  3.4.2. Band theory of solids  3.4.3. Superconductors  3.4.4. Defects in the crystal  3.5. Lanthanides and Actinides  3.5.1. Electronic configuration in lanthanides and actinides  3.5.2. Coordination chemistry of the lanthanides  3.5.3. Magnetic Properties of Lanthanides
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.2. Spectroscopic Techniques  4.2.1. Atomic absorption spectroscopy  4.2.2. X-ray diffraction  4.2.3. Inductively coupled plasma spectroscopy  4.3. Electroanalytical methods  4.3.1. Potentiometry  4.3.2. Voltammetry  4.3.3. Colometry  4.4. Mass Spectrometry  4.4.1. Ionization Technique  4.4.2. Fragmentation Pattern  4.5. Chemometrics  4.5.1. Multidisciplinary analysis  4.5.2. Machine Learning in Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.1.1. Force fields and energy minimization  5.1.2. Monte Carlo simulation in molecular dynamics simulations  5.2. Quantum chemical methods  5.2.1. Hartree–Fock theory  5.2.2. Density functional theory  5.2.3. Semi-empirical methods  5.3. Computational drug design  5.3.1. Molecular Docking  5.3.2. QSAR Modeling  5.3.3. Virtual Screening
  6. Biochemistry  6.1. Enzyme Kinetics  6.1.1. Michaelis-Menten kinetics  6.1.2. Inhibition mechanism  6.2. Metabolism and Bioenergetics  6.2.1. Glycolysis  6.2.2. Citric acid cycle  6.2.3. Electron transport chain  6.3. molecular Biology  6.3.1. DNA replication and repair  6.3.2. Protein synthesis  6.3.3. Gene Regulation  6.4. Structural Biochemistry  6.4.1. Protein Folding  6.4.2. Membrane Biophysics
  7. Environmental Chemistry  7.1. Atmospheric Chemistry  7.1.1. Greenhouse gases  7.1.2. Ozone depletion  7.1.3. Air pollutants and smoke  7.2. Water Chemistry  7.2.1. pH and water hardness  7.2.2. Wastewater treatment  7.2.3. Aquatic Chemistry  7.3. Soil Chemistry  7.3.1. Heavy metal contamination  7.3.2. Soil pH and Buffering  7.3.3. Nutrient cycling  7.4. Toxicology and Chemical Safety  7.4.1. Toxicokinetics  7.4.2. Risk Assessment in Toxicology and Chemical Safety in Environmental Chemistry  7.4.3. Effects of pollutants on the environment

Graduate → Analytical chemistry ↓


Spectroscopic Techniques


Spectroscopic techniques play a vital role in analytical chemistry, providing important information about the molecular structure, composition, and dynamics of substances. These techniques rely on the interaction between electromagnetic radiation and matter, leading to the absorption, emission, or scattering of light. With a wide range of applications in areas such as pharmaceuticals, environmental monitoring, and food safety, spectroscopic techniques are fundamental to modern chemical analysis. Below, we discuss several key spectroscopic methods, exploring their principles, applications, and advantages one by one.

1. Fundamentals of spectroscopy

Spectroscopy involves the study of the interaction between electromagnetic radiation and matter. When light interacts with a molecule, it may be absorbed or emitted, depending on the energy levels involved. The basic relation governing these interactions is given as:

e = hν = hc/λ

Where:

  • E = energy of the photon
  • h = Planck's constant (6.626 x 10 -34 joules s)
  • ν = frequency of radiation
  • c = speed of light (3.00 x 10 8 m/s)
  • λ = wavelength of the radiation

The absorption or emission of radiation occurs at specific wavelengths corresponding to the energy differences between the quantized states of the molecule.

2. Types of spectroscopic techniques

Spectroscopic techniques can be broadly classified based on the type of electromagnetic radiation used or the type of interaction observed. These include:

  • UV-visible spectroscopy
  • Infrared (IR) spectroscopy
  • Nuclear Magnetic Resonance (NMR) spectroscopy
  • Mass spectrometry (MS)
  • Raman spectroscopy
  • X-ray spectroscopy

Each technique provides unique insights into molecular properties and serves different analytical purposes.

3. UV-visible spectroscopy

UV-visible spectroscopy is based on the absorption of ultraviolet and visible light by molecules, causing electronic transitions. It is widely used to determine the concentration of substances in solution.

A = εcl

Where:

  • A = Absorption
  • ε = molar absorptivity
  • c = concentration of the solution
  • l = path length of the sample cell

UV-visible spectroscopy is helpful in quantifying nucleic acids, proteins, and other biological macromolecules.

Example visual representation of UV-visible absorption:

4. Infrared (IR) spectroscopy

Infrared spectroscopy measures molecular vibrations produced by changes in dipole moments when molecules absorb IR radiation. It is particularly useful for identifying functional groups.

Specific absorption in IR:

Functional Group Wave number (cm -1)
OH (alcohol) 3200-3600
C=O (carbonyl) 1700-1750
CH (Alkanes) 2800-3000

Example visual representation of the IR spectrum:

5. Nuclear Magnetic Resonance (NMR) spectroscopy

NMR spectroscopy uses the magnetic properties of certain atomic nuclei. When placed in a magnetic field, these nuclei resonate at specific frequencies, providing detailed information about molecular structure, dynamics, and environment.

Chemical shift is a key aspect of NMR and is defined as:

δ = (ν - ν ref) / ν ref x 10 6

where ν is the sampling frequency, and ν ref is the reference frequency.

Example visual representation of NMR chemical shifts:

6. Mass spectrometry (MS)

Mass spectrometry is a powerful analytical technique that determines the mass-to-charge ratio of ions. It is important for elucidating molecular structures, identifying unknown compounds, and quantifying known materials.

The mass spectrum displays peaks corresponding to different isotopes or fragments of a molecule.

Example representation of a mass spectrum:

7. Raman spectroscopy

Raman spectroscopy is based on the scattering of light, with most of the light being scattered elastically (Rayleigh scattering), but a small fraction being scattered inelastically with a different frequency (Raman scattering). It is used to obtain vibrational information similar to IR spectroscopy, but with some advantages such as water not interfering, making it excellent for aqueous solutions.

The Raman effect can be expressed in terms of an energy change:

ΔE = hv̅ (1 – r)

where v̅ is the initial frequency, and R is the vibrational transition.

Visual illustration of Raman scattering:

8. X-ray spectroscopy

X-ray spectroscopy involves the interaction of X-rays with matter, causing internal electrons to be excited to higher energy states. It is particularly useful for studying metal complexes and inorganic systems, providing insight into electron configuration and structural properties.

X-ray absorption based on the Beer-Lambert law:

I = I 0 e -μx

Where:

  • I = intensity after absorption
  • I 0 = initial intensity
  • μ = absorption coefficient
  • x = length of the path

Conclusion

Spectroscopic techniques are indispensable tools in analytical chemistry, each of which provides unique insights into the nature of substances. Whether it is evaluating purity through UV-visible spectroscopy, identifying functional groups by IR spectroscopy, determining structure using NMR, analyzing mass with mass spectrometry, exploring vibrational states through Raman spectroscopy, or understanding electronic settings in X-ray spectroscopy, these methods provide comprehensive solutions for a myriad of chemical analyses.


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Spectroscopic Techniques

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