Electrosynthesis

Done by

Krishnaprasad K.A.

Antriksh Rathore

L. Narayana

D.J. Vineeth

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.

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.

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.

Reactions

• 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

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 α-position. The intermediate oxonium ion is trapped by a nucleophile usually solvent.

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 α-methoxylation of N-carbomethoxypyrrolidine

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:

Cathodic Reductions

• 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:

• 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:

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.

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.

Research & Development

• Electrochemical expertise in electrosynthesis includes the following fields: – 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

Inorganic Compounds Synthesis

• 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: – 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

Organic Compound Synthesis

• 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:– Nitro Reduction– Halogenation – Methoxylation– Acetoxylation – Hydrogenation – Carboxylation – Coupling Reactions– Acetamidation– Dehalogenation– Cyanation

ENERGY STORAGE USING ELECTROSYNTHESIS

Energy Storage

• 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.

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.

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)