Ionic liquids as an electrolyte for the electro synthesis of organic compounds

Abstract

The use of ionic liquids (ILs) as a solvent and an electrolyte for electro organic synthesis has been reviewed. To date several ILs exist, however the ILs based on tetraalkylammonium, pyrrolidinium, piperidinium and imidazolium cations with BF4(-), PF6(-), and TFSI anions have been widely used and explored the most. Electro organic synthesis in ionic liquid media leading to the synthesis of a wide range of organic compounds has been discussed. Anodic oxidation or cathodic reduction will generate radical cation or anion intermediates, respectively. These radicals can undergo self coupling or coupling with other molecules yielding organic compounds of interest. The cation of the IL is known to stabilize the radical anion extensively. This stabilization effect has a specific impact on the electrochemical CO2 reduction and coupling to various organics. The relative stability of the intermediates in IL leads to the formation of specific products in higher yields. Electrochemical reduction of imidazolium or thiazolium based ILs generates N-heterocyclic carbenes that have been shown to catalyze a wide range of base or nucleophile catalyzed organic reactions in IL media, an aspect that falls into the category of organocatalysis. Electrochemical fluorination or selective electrochemical fluorination is another fascinating area that delivers selectively fluorinated organic products in Et3N·nHF or Et4NF·nHF adducts (IL) via anodic oxidation. Oxidative polymerization in ILs has been explored the most; although morphological changes were observed compared to the conventional methods, polymers were obtained in good yields and in some cases ILs were used as dopants to improve the desired properties.

Electrocatalytic studies on imidazolium based ionic liquids: defining experimental conditions

“…Room temperature ionic liquids (RTILs) or low temperature molten salts [1] have emerged as promising media to improve performance in electrochemical applications and devices. In particular, RTILs provide new interesting results in electrochemical sensors [2,3], electrosynthesis of organic compounds via alternative routes [4] and synthesis of functional materials with imidazolium-based RTILs for various and relevant applications [5][6][7][8]. In addition to this, the use of RTILs in the field of energy conversion and storage is a promising field, for instance, in redox flow batteries [9], supercapacitors [10] and electrocatalytic reactions such as oxygen reduction reaction [11], CO electrooxidation [12][13] and CO 2 electroreduction [14][15][16][17][18], among others.…”

Thermochemistry of Pyridinium Based Ionic Liquids with Tetrafluoroborate Anion

“…Due to specific physicochemical properties, they are able to increase both the reactivity and/or selectivity of a number of industrially important processes . The use of ILs as a solvent and an electrolyte has been shown to be successful for electro organic synthesis . To date the ILs based on piperidinium, tetraalkylammonium, pyrrolidinium, and imidazolium cations with [BF 4 ] – , [PF 6 ] – , and [NTf 2 ] – anions have been explored and widely used the most.…”

“…[1] The use of ILs as a solvent and an electrolyte has been shown to be successful for electro organic synthesis. [2] To date the ILs based on piperidinium, tetraalkylammonium, pyrrolidinium, and imidazolium cations with [BF 4 ] -, [PF 6 ] -, and [NTf 2 ]anions have been explored and widely used the most. In the focus of current study are pyridinium based ILs with the BF 4 anion.…”

Electrochemistry and Photoredox Catalysis: A Comparative Evaluation in Organic Synthesis

“…Tajima, Fuchigami and co-workers showed that also solid-supported bases could serve as a similar solution by in situ generation of the electrolyte from methanol or HFIP as multifunctional solvents [201,202,203,204]. Ionic liquids can also be used as the solvent as well as the electrolyte in electrosynthesis [205,206].…”