2. What is Electrosynthesis?
• Electrosynthesis in organic chemistry is the synthesis of
chemical compounds in an electrochemical cell.
• The main advantage of electrosynthesis over an ordinary
redox reaction is avoidance of the potential wasteful
other half-reaction and the ability to precisely tune the
required potential.
3. Experimental Setup
• The basic setup in electrosynthesis is a galvanic cell, a potentiostat
and two electrodes. Good electrosynthetic conditions use a solvent
and electrolyte combination that minimizes electrical resistance.
• Electrodes are selected which provide favorable electron transfer
properties towards the substrate while maximizing the activation
energy for side reactions.
4. Experimental Setup
• The two basic cell types are undivided cell or divided cell type.
• In divided cells the cathode and anode chambers are separated with
a semiporous membrane.
• The purpose of the divided cell is to permit the diffusion of ions while
restricting the flow of the products and reactants. This is important
when unwanted side reactions are possible.
5. Reactions
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Organic oxidations take place at the anode with initial formation of radical
cations as reactive intermediates. Compounds are reduced at the cathode to
radical anions. The initial reaction takes place at the surface of the electrode
and then the intermediates diffuse into the solution where they participate in
secondary reactions.
The potential drop between the electrodes determines the rate constant of
the reaction. Electro synthesis is carried out with either constant potential or
constant current.
Reactions involved:
– Anodic oxidations
– Cathodic Reduction
– Electrofluorination
6. Anodic Oxidations
• The most well-known electrosynthesis is the Kolbe
electrolysis.
• A variation is called the non-Kolbe reaction when a
heteroatom (nitrogen or oxygen) is present at the αposition. The intermediate oxonium ion is trapped by a
nucleophile usually solvent.
7. Anodic Oxidations
• In the so-called Crum Brown–Walker reaction an aliphatic
dicarboxylic acid is oxidized forming the elongated di-acid, for
example the formation of the dimethyl ester of decanedioic acid from
methyl hydrogen hexanedioate.
• Amides can be oxidized through a N-acyliminium ion which can be
captured by a nucleophile:
This reaction type is called a Shono oxidation. An example is the αmethoxylation of N-carbomethoxypyrrolidine
8. Cathodic Reductions
• In the Markó-Lam deoxygenation, an alcohol could be almost
instantaneously deoxygenated by electroreducing their toluate ester.
• The cathodic hydroisomerization of activated olefins is applied
industrially in the synthesis of adiponitrile from 2 equivalents of
acrylonitrile:
9. Cathodic Reductions
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The cathodic reduction of arene compounds to the 1,4-dihydro derivatives is
similar to a Birch reduction. Examples from industry are the reduction of
phthalic acid:
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The Tafel rearrangement (Julius Tafel, 1907) at one time was relevant to the
synthesis of certain hydrocarbons from alkylated ethyl acetoacetate, a
reaction accompanied by the rearrangement reaction of the alkyl group:
10. Electrofluorination
• In organofluorine chemistry, many perfluorinated compounds are
prepared by electrochemical synthesis, which is conducted in liquid
HF at voltages near 5–6 V using Ni anodes.
• Amines, alcohols, carboxylic acids, and sulfonic acids are converted
to the perfluorinated derivatives using this technology.
• A solution or suspension of the hydrocarbon in hydrogen fluoride is
electrolyzed at 5–6 V to produce high yields of the perfluorinated
product.
11. Electrosynthesis Inc.
• Electrosynthesis Company, Inc. specializes in the
development of electrochemical technologies for energy
storage systems, fuel
cells, electrodialysis, separations, sensors, synthesis of
inorganic and organic chemicals and recycling of waste
streams.
12. Research & Development
• Electrochemical expertise in electrosynthesis includes the following
fields:
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Electrosynthesis of inorganic and organic (including pharmaceuticals) compounds
Energy Storage
Batteries and fuel cells
Electrodialysis: take the next steps in our state-of-the art ED facility.
Membrane separation processes including salt splitting
Sensors
Environmental electrotechnology: water purification; metal recovery; pollutant
destruction; recovery, recycle and reuse
13. Inorganic Compounds
Synthesis
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Electrochemical synthesis of inorganic compounds offers several
advantages over conventional synthesis and often provides the only viable
route. Electrosynthetic processes can often be run under milder operating
conditions with fewer chemical reagents.
Examples:
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Chlor-alkali manufacture
Aluminum Refining
Water Electrolysis to produce hydrogen and oxygen
Manufacture of bromine, fluorine, chlorate, perchlorate, persulfate, ferrate, peroxide, etc.
Metals extraction and refining: Al, Na, Mg, Li, etc.
Metal oxides manufacture
14. Organic Compound
Synthesis
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Industrial scale electrochemical processing of organic chemicals has been
practiced for almost 100 years. An estimated 120 different processes have
been piloted at various scales and at least 60 are now commercial. The
biggest of these is the electrohydrodimerization of acrylonitrile to adiponitrile
a key constituent in the production of Nylon.
Other examples of reactions that can be carried out electrochemically include:
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Nitro Reduction
Halogenation
Methoxylation
Acetoxylation
Hydrogenation
Carboxylation
Coupling Reactions
Acetamidation
Dehalogenation
Cyanation
16. Energy Storage
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The Electrosynthesis Company has considerable experience developing energy
storage technologies including electrochemical capacitors, batteries and regenerative
fuel cells or redox flow batteries.
Electrosynthesis formed a key part of the Research and Development group for
Regenesys Technologies Ltd developing larger scale energy storage systems for use
on the electricity grid. This technology was based on a polysulfide/bromide system.
The redox flow battery is a form of rechargeable battery in which electrolyte
containing one or more dissolved electroactive species flows through an
electrochemical cell that, on charge, converts electricity into chemical energy. The
electrolyte, and therefore energy, is stored externally in tanks until the energy is
required when the solution is pumped back into the electrochemical cell discharging
the chemical energy as electrical energy.
17. Advantages of E.S.
Advantages:
• This is one of only a few technologies that can separate energy and
power requirements. Power is determined by the size of the
electrochemical cell whereas the energy is proportional to the size of
the storage tanks.
• Large amounts of energy (up to hundreds of MWh) can be stored
until required with little loss.
• High efficiency conversion from electrical to chemical energy
• Long cycle life with quick response times.
18. Applications of E.S.
Applications
• Large (1 kWh - many MWh) stationary applications.
• Load leveling: store energy during times of low demand and provide
electricity during peak time.
• Storing energy from renewable sources such as wind or solar to
supply power during low generation periods.
• Uninterrupted power supply (UPS), to provide power when main
power fails.
• Remote area power supplies (RAPS)
