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A topic from the subject of Synthesis in Chemistry.

  • 10 months ago
  • 3 min read
Photochemical and Electrochemical Synthesis
Introduction
Photochemical and electrochemical synthesis are two powerful techniques for the synthesis of organic compounds. Photochemical synthesis involves the use of light to initiate chemical reactions, while electrochemical synthesis involves the use of electricity.
Basic Concepts
Photochemical Synthesis
Photochemistryis the study of the interaction of light with matter. Photochemical reactions are chemical reactions that are initiated by the absorption of light.
The wavelength of lightabsorbed by a molecule determines the type of photochemical reaction that will occur. Common photochemical reactions include photoaddition, photocycloaddition, and photooxidation.
Electrochemical Synthesis
Electrochemistryis the study of the relationship between electricity and chemical change. Electrochemical reactions are chemical reactions that are driven by the flow of electricity.
An electrochemical cellconsists of two electrodes (anode and cathode) immersed in an electrolyte solution. When a potential difference is applied to the electrodes, electrons flow from the anode to the cathode.
The electrons* can then be used to reduce or oxidize the reactants in the electrolyte solution.
Equipment and Techniques
Photochemical Synthesis
Light sourcesfor photochemical synthesis include UV lamps, lasers, and sunlight. Reaction vessels for photochemical synthesis are typically made of quartz or Pyrex glass.
Solvents* for photochemical synthesis include water, methanol, and dichloromethane.
Electrochemical Synthesis
Electrochemical cellsfor electrochemical synthesis can be divided into two categories:divided cellsandundivided cells. Divided cells have a membrane that separates the anode and cathode compartments.
Undivided cellsdo not have a membrane. Electrodes for electrochemical synthesis are typically made of platinum, gold, or carbon.
Electrolyte solutions* for electrochemical synthesis include aqueous solutions of salts, acids, and bases.
Types of Experiments
Photochemical Synthesis
Photoaddition reactionsinvolve the addition of two or more molecules to a double bond. Photocycloaddition reactions involve the addition of two or more molecules to a triple bond.
Photooxidation reactions* involve the oxidation of a molecule by light.
Electrochemical Synthesis
Reductionsare electrochemical reactions that involve the addition of electrons to a molecule. Oxidations are electrochemical reactions that involve the removal of electrons from a molecule.
Coupling reactions* are electrochemical reactions that involve the formation of a new bond between two molecules.
Data Analysis
Photochemical synthesisexperiments can be analyzed usingUV-Vis spectroscopy,HPLC, andGC-MS. Electrochemical synthesis experiments can be analyzed using cyclic voltammetry, chronoamperometry, and coulometry.
Applications
Photochemical synthesisis used to synthesize a wide variety of organic compounds, including pharmaceuticals, agrochemicals, and materials. Electrochemical synthesis is used to synthesize a wide variety of inorganic and organic compounds, including metals, semiconductors, and polymers.
Conclusion
Photochemical and electrochemical synthesis are two powerful techniques for the synthesis of organic compounds. These techniques offer a number of advantages over traditional synthetic methods, including high yields, selectivity, and environmentally friendly.
Photochemical and Electrochemical Synthesis
Key Points

  • Photochemical synthesis involves the use of light energy to initiate chemical reactions.
  • Electrochemical synthesis involves the use of electrical energy to initiate chemical reactions.
  • Both photochemical and electrochemical synthesis can be used to synthesize complex molecules from simpler starting materials.
  • Photochemical and electrochemical synthesis are often more environmentally friendly than traditional synthetic methods.

Main Concepts

Photochemical synthesis is a chemical reaction that is initiated by the absorption of light energy. The absorbed energy is used to excite an electron in the molecule, which can then react with other molecules to form new bonds.


Electrochemical synthesis is a chemical reaction that is initiated by the application of an electrical current. The electrical current causes the oxidation or reduction of molecules, which can then react with each other to form new bonds.


Photochemical and electrochemical synthesis are both powerful tools for the synthesis of complex molecules. They can be used to synthesize a wide variety of compounds, including organic molecules, inorganic molecules, and organometallic compounds.


Photochemical and electrochemical synthesis are often more environmentally friendly than traditional synthetic methods. They do not require the use of harsh chemicals or solvents, and they can be carried out under mild conditions.


Photochemical Synthesis: Synthesis of 1,4-Diphenylbutadiene
Materials:

  • Stilbene (1 g)
  • Benzene (50 mL)
  • Ultraviolet lamp

Procedure:

  1. Dissolve stilbene in benzene.
  2. Irradiate the solution with ultraviolet light for several hours.
  3. Filter the solution to remove any unreacted stilbene.
  4. Evaporate the solvent to obtain the product.

Observations:

  • The solution changes color from colorless to yellow during irradiation.
  • A precipitate of 1,4-diphenylbutadiene forms upon filtration.

Results:

  • The ultraviolet light causes the stilbene molecule to undergo a [2+2] cycloaddition reaction, forming 1,4-diphenylbutadiene.

Significance:

  • This experiment demonstrates the use of ultraviolet light as an energy source to drive a chemical reaction.
  • Photochemical reactions are often used to synthesize complex organic molecules that are difficult or impossible to prepare by other methods.

Electrochemical Synthesis: Electrolysis of Water
Materials:

  • Water
  • Graphite electrodes
  • Power supply

Procedure:

  1. Fill a beaker with water.
  2. Immerse the graphite electrodes in the water.
  3. Connect the electrodes to the power supply.
  4. Turn on the power supply and adjust the voltage to 5V.
  5. Observe the bubbles that form on the electrodes.

Observations:

  • Bubbles of oxygen form on the positive electrode (anode).
  • Bubbles of hydrogen form on the negative electrode (cathode).

Results:

  • The electrolysis of water produces hydrogen and oxygen gas.
  • The reaction at the anode is: 2H2O(l) -> O2(g) + 4H+(aq) + 4e-.
  • The reaction at the cathode is: 4H+(aq) + 4e- -> 2H2(g).

Significance:

  • This experiment demonstrates the use of electricity to drive a chemical reaction.
  • Electrochemical synthesis is often used to produce large quantities of chemicals, such as hydrogen and chlorine.

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