Ionic liquid with acidic properties is an important branch in the wide ionic liquid field and the aim of this article is to cover all aspects of these acidic ionic liquids, especially focusing on the developments in the last four years. The structural diversity and synthesis of acidic ionic liquids are discussed in the introduction sections of this review. In addition, an unambiguous classification system for various types of acidic ionic liquids is presented in the introduction. The physical properties including acidity, thermo-physical properties, ionic conductivity, spectroscopy, and computational studies on acidic ionic liquids are covered in the next sections. The final section provides a comprehensive review on applications of acidic ionic liquids in a wide array of fields including catalysis, CO2 fixation, ionogel, electrolyte, fuel-cell, membrane, biomass processing, biodiesel synthesis, desulfurization of gasoline/diesel, metal processing, and metal electrodeposition.

Acidic Ionic Liquids.

The synthetic utility of organohypervalent iodine reagents will be illustrated by their use in the α-hydroxydimethylacetal formation reaction from enolizable ketones, α-hydroxylation, α-tosyloxylation, α-alkoxylation and arylation of ketones, carbon−carbon bond formation, and intramolecular cyclopropanation using iodonium ylides. The uses of these reagents in the Hunsdiecker reaction of carboxylic acids and Hofmann rearrangement of carboxamides is presented. Specific transformation in the cubane series are discussed. The syntheses of a wide range of heterocycle structures are also presented. A unifying pathway for virtually all these diverse reactions is offered; the central features being initial attack at the iodonium center, ligand coupling, with reductive elimination of iodobenzene to yield the product.

Organohypervalent iodine: development, applications, and future directions.

https://pubs.rsc.org/en/content/articlepdf/2017/gc/c7gc00705a

An economically viable ionic liquid for the fractionation of lignocellulosic biomass

Synthesis and application of task-specific ionic liquids used as catalysts and/or solvents in organic unit reactions

Alkylrhenium oxides as homogeneous epoxidation catalysts: Activity, selectivity, stability, deactivation

Esterification of acetic acid with 1-octanol was studied using a series of alkylammonium salts as Bronsted acidic ionic liquids. The following ionic liquids were prepared and used as catalysts and mediums in the esterification reaction; [Et3NH][HSO4], [Et3NH][H2PO4], [Et3NH][BF4], [Et3NH][p-CH3C6H4SO3], [Et2(PhCH2)NH][HSO4], [n-Bu3NH][HSO4], [n-Oct3NH][HSO4], [Et2NH2][HSO4], [Et2NH2][H2PO4], [Et2NH2][BF4], [i-Pr2NH2][HSO4], [EtNH3][HSO4], [EtNH3][H2PO4], and [EtNH3][BF4]. Higher acidity of the anion in the ionic liquid resulted in high yield of the ester. Yield of the ester decreased with increase in the size of the cation. There was no phase separation in the reactions where size of anion and/or cation was bigger.

Brønsted acidic ionic liquids derived from alkylamines as catalysts and mediums for Fischer esterification: Study of structure–activity relationship

Epoxidation of alkenes with iodosylbenzene using mono-and binuclear Ru(III)-Schiff base complex catalysts

The mixed ligand complexes Cr III (dpa)(L)Cl and Fe III (dpa)(L)(H 2 O) n Cl (where dpa = dipicolinic acid, l = ethylenediamine, 2,2-bipyridine or 1,10-phenanthroline, n = 1 or 2) were synthesized and characterized by elemental analysis and spectral, magnetic, conductance and electrochemical studies. The complexes were evaluated for their activity as catalysts for the epoxidation of olefins. The chromium complexes catalyzed epoxidation of olefins, viz., norbornene, cis -cyclooctene, styrene and cyclohexene with iodosylbenzene, to give corresponding epoxides. Oxidation of cyclohexene gave allylic oxidation products besides the epoxide. The iron complexes were nearly inactive as epoxidation catalysts under these conditions. Spectrophotometric and electrochemical measurements were used to deduce the cause of low catalytic activity.

Mixed ligand complexes of chromium(III) and iron(III): synthesis and evaluation as catalysts for oxidation of olefins

Epoxidation of olefins catalysed by Mn(III)-Schiff base complexes

Triethylammonium sulfate, triethylammonium dihydrogen phosphate and triethylammonium tetrafluoroborate were applied as ionic liquid catalyst and medium for the esterification of carboxylic acids with primary alcohols. Esterification of aliphatic carboxylic acids in the presence of triethylammonium sulfate gave the corresponding esters in excellent yield. The ionic liquid and ester formed separate phases in the reaction facilitating separation of the product.

Pralhad A. Ganeshpure

Papers

Brønsted acidic ionic liquids derived from alkylamines as catalysts and mediums for Fischer esterification: Study of structure–activity relationship

Epoxidation of alkenes with iodosylbenzene using mono-and binuclear Ru(III)-Schiff base complex catalysts

Mixed ligand complexes of chromium(III) and iron(III): synthesis and evaluation as catalysts for oxidation of olefins

Epoxidation of olefins catalysed by Mn(III)-Schiff base complexes

Application of triethylammonium salts as ionic liquid catalyst and medium for Fischer esterification