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 → Functional Group ↓


Thiols and sulfides


In the vast world of organic chemistry, thiols and sulfides are major functional groups that contain sulfur. They are helpful in biochemistry and are fundamental in a variety of organic reactions and industrial processes. In this understandable guide, we will explore their structures, properties, nomenclature, occurrences, and reactions with clarity for undergraduate students.

Introduction to thiols and sulfides

Thiols and sulfides are sulfur-containing organic compounds. The functional group in a thiol is equivalent to an alcohol (hydroxyl group) in which the oxygen is replaced by a sulfur atom, giving it a unique set of properties. Sulfides, on the other hand, are analogous to ethers, where the oxygen atom in ether is replaced by a sulfur atom.

Thiols

Thiols, also known as mercaptans, are characterized by the presence of a sulfhydryl group, that is, a sulfur atom bonded to a hydrogen atom. The general formula for thiols can be represented as R-SH, where R represents an alkyl or aryl group.

Chemical structure of thiols

      H
      ,
    RSH

In this structure, SH bond is similar to the hydroxyl group in alcohols, but the presence of sulfur gives it distinctive chemical properties.

Naming of thiols

When naming thiols, the suffix "-thiol" is added to the name of the parent compound. For example:

  • CH 3 -SH is called methanethiol.
  • C 2 H 5 -SH is called ethanethiol.
  • C 6 H 5 -SH is benzenethiol or more commonly called thiophenol.

Properties of thiols

Thiols have a characteristic odor, often described as unpleasant and similar to rotten eggs or garlic. This property is due to the ease of forming hydrogen bonds by SH bond. Let us consider some important characteristics of thiols:

  • Thiols are more acidic than alcohols. The S-H bond is less polar than the O-H bond, but the hydrogen atom can still release a proton under the right conditions.
  • Thiols form disulfides through oxidation, which is an important reaction in biochemistry, particularly in the stabilization of proteins via disulfide bridges.
  • They are less soluble in water than alcohols of similar molecular weight, mainly due to weaker hydrogen bonds.

Reactions of thiols

The reactivity of thiols is primarily centered around the sulfhydryl group. Some common reactions include:

Thiols oxidation

Thiols can be oxidized to form disulfides. This is an important reaction, especially in biological systems where disulfide bonds help maintain the structure of proteins.

      2 R-SH + 1/2 O 2 → RSSR + H 2 O

Thiolation

Thiols can react with alkyl halides to form thioethers or sulfides.

      R-SH + R'-X → RSR' + HX

Sulfides

Sulfides, also called thioethers, contain a sulfur atom bonded to two alkyl or aryl groups. The general formula for sulfides is RS-R'.

Chemical structure of sulfides

      RSR'

Like ethers, sulfides also contain sulfur connecting two carbon groups. However, the lower electronegativities of sulfur compared to oxygen give sulfides different properties.

Naming of sulfides

Sulfide nomenclature identifies the two organic groups located on either side of the sulfur atom, followed by the word "sulfide." Here are some examples:

  • CH 3 -S-CH 3 is called dimethyl sulfide.
  • CH 3 -SC 2 H 5 is called ethyl methyl sulfide.

Properties of sulfides

  • Sulfides have a characteristic odor that is generally less unpleasant than that of thiols.
  • They are chemically more stable than thiols and have a lesser tendency to form hydrogen bonds.
  • Sulfides are generally nonpolar, making them less soluble in water, but more soluble in organic solvents.

Reactions of sulfides

The chemistry of sulfides involves a number of nuclear reactions, many of which involve the breaking or modification of SC bond.

Oxidation

Sulfides can be oxidized to sulfoxides and further to sulfones.

      RSR' + [O] → RS(=O)-R' (sulphoxide)

      RS(=O)-R' + [O] → RS(=O) 2 -R' (sulfone)

Translations alkylation

Sulfides can undergo alkylation to form more complex sulfides. For example:

      RSR' + R''-X → RS-R''R' + X -

Occurrence and applications

Thiols and sulfides are prevalent not only in laboratories but also in nature and industry. They play important roles in a variety of contexts:

  • Thiols are important in the structure and function of biological molecules such as enzymes and proteins. For example, the amino acid cysteine contains a thiol group.
  • The disulfide bond, a product of thiol oxidation, is essential for protein folding and stability.
  • Sulfides are found in many medications and pesticides. They are also found in the volatile components of some foods, which contribute to flavor and aroma.
  • In industrial applications, thiols are used in detecting gas leaks due to their strong odor.

Biological significance

The role of thiols in biochemistry cannot be underestimated. The free thiol group in cysteine residues of proteins can form disulfide bridges, which are important for maintaining the tertiary and quaternary structure of proteins.

Thiols are also part of the cellular redox system and contribute to regulation and signaling pathways, especially in oxidative stress responses.

Conclusion

Understanding the chemistry of thiols and sulfides opens the door to more comprehensive knowledge in organic and biochemistry. Their unique properties and reactivity play a key role in chemical reactions and practical applications, from drug synthesis to understanding the structural dynamics of proteins.


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