Vasuki Tambyrajah

Bio: Vasuki Tambyrajah is an academic researcher from University of Leicester. The author has contributed to research in topics: Ionic liquid & Friedel–Crafts reaction. The author has an hindex of 11, co-authored 16 publications receiving 3810 citations. Previous affiliations of Vasuki Tambyrajah include University of Leeds.

Ionic liquids and their use as solvents

Abstract: Ionic compounds with a freezing point of up to 100 °C are formed by the reaction of an one amine salt of formula (I) R?1 R2 R3 R4 N+ X-?, such as choline chloride with an organic compound (II) capable of forming a hydrogen bond with X-, such as urea, wherein the molar ratio of I to II is from 1:1.5 to 1:2.5. R?1, R2, R3 and R4? may be H, optionally substituted C?1? to C5 alkyl, optionally substituted C6 to C10 cycloalkyl, optionally substituted C6 to C12 aryl, optionally substituted C7 to C12 alkaryl, or R?1 and R2? taken together may represent a C?4? to C10 optionally substituted alkylene group, thereby forming with the N atom of formula I a 5 to 11-membered heterocyclic ring and all of R?1, R2, R3 and R4? are not identical, X- may be NO?3??-, F, CI-, Br-, I-, BF?4-, CIO4?-, CN-, SO?3CF3-, or COOCF?3?-. The ionic compounds are useful as solvents, and electrolytes for example in electroplating, electrowinning, and electropolishing, and as catalysts.

Applications of ionic liquids in the chemical industry

Abstract: In contrast to a recently expressed, and widely cited, view that “Ionic liquids are starting to leave academic labs and find their way into a wide variety of industrial applications”, we demonstrate in this critical review that there have been parallel and collaborative exchanges between academic research and industrial developments since the materials were first reported in 1914 (148 references)

Deep eutectic solvents: syntheses, properties and applications

Abstract: Within the framework of green chemistry, solvents occupy a strategic place. To be qualified as a green medium, these solvents have to meet different criteria such as availability, non-toxicity, biodegradability, recyclability, flammability, and low price among others. Up to now, the number of available green solvents are rather limited. Here we wish to discuss a new family of ionic fluids, so-called Deep Eutectic Solvents (DES), that are now rapidly emerging in the current literature. A DES is a fluid generally composed of two or three cheap and safe components that are capable of self-association, often through hydrogen bond interactions, to form a eutectic mixture with a melting point lower than that of each individual component. DESs are generally liquid at temperatures lower than 100 °C. These DESs exhibit similar physico-chemical properties to the traditionally used ionic liquids, while being much cheaper and environmentally friendlier. Owing to these remarkable advantages, DESs are now of growing interest in many fields of research. In this review, we report the major contributions of DESs in catalysis, organic synthesis, dissolution and extraction processes, electrochemistry and material chemistry. All works discussed in this review aim at demonstrating that DESs not only allow the design of eco-efficient processes but also open a straightforward access to new chemicals and materials.

Aryl-aryl bond formation by transition-metal-catalyzed direct arylation.

Abstract: The biaryl structural motif is a predominant feature in many pharmaceutically relevant and biologically active compounds. As a result, for over a century 1 organic chemists have sought to develop new and more efficient aryl -aryl bond-forming methods. Although there exist a variety of routes for the construction of aryl -aryl bonds, arguably the most common method is through the use of transition-metalmediated reactions. 2-4 While earlier reports focused on the use of stoichiometric quantities of a transition metal to carry out the desired transformation, modern methods of transitionmetal-catalyzed aryl -aryl coupling have focused on the development of high-yielding reactions achieved with excellent selectivity and high functional group tolerance under mild reaction conditions. Typically, these reactions involve either the coupling of an aryl halide or pseudohalide with an organometallic reagent (Scheme 1), or the homocoupling of two aryl halides or two organometallic reagents. Although a number of improvements have developed the former process into an industrially very useful and attractive method for the construction of aryl -aryl bonds, the need still exists for more efficient routes whereby the same outcome is accomplished, but with reduced waste and in fewer steps. In particular, the obligation to use coupling partners that are both activated is wasteful since it necessitates the installation and then subsequent disposal of stoichiometric activating agents. Furthermore, preparation of preactivated aryl substrates often requires several steps, which in itself can be a time-consuming and economically inefficient process.

Deep Eutectic Solvents Formed between Choline Chloride and Carboxylic Acids: Versatile Alternatives to Ionic Liquids

Abstract: Deep Eutectic Solvents (DES) can be formed between a variety of quaternary ammonium salts and carboxylic acids. The physical properties are significantly affected by the structure of the carboxylic acid but the phase behavior of the mixtures can be simply modeled by taking account of the mole fraction of carboxylic acid in the mixture. The physical properties such as viscosity, conductivity, and surface tension of these DES are similar to ambient temperature ionic liquids and insight into the cause of these properties is gained using hole-theory. It is shown that the conductivity and viscosity of these liquids is controlled by ion mobility and the availability of voids of suitable dimensions, and this is consistent with the fluidity of other ionic liquids and molten salts. The DES are also shown to be good solvents for metal oxides, which could have potential application for metal extraction.