IONIC LIQUIDS
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The document discusses ionic liquids as green solvents for organic transformations. It covers topics such as green chemistry principles, the structure and properties of ionic liquids that make them suitable green solvent replacements. Ionic liquids have applications in various organic reactions as solvents, allowing for higher yields, selectivity and easier product separation compared to conventional organic solvents. Examples of reactions discussed include Diels-Alder, Heck, hydrogenation and ring-opening reactions. Different types of ionic liquids are also summarized, including functionalized and deep eutectic solvents.
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IONIC LIQUIDS
- 1. IONIC LIQUIDS AS GREEN SOLVENTS FOR ORGANIC TRANFORMATIONS Submitted by: SANSKRITA MADHUKAILYA M.Sc Dept. of Chemistry, Dibrugarh University
- 2. TOPICS TO BE COVERED : Green Chemistry & Principles of green chemistry Ionic liquids, Structure & Historical developments Synthesis of ionic liquids Properties of ionic liquids that separates it from other solvents Applications Ionic liquids in different organic solvents Various types of ionic liquids References
- 3. GREEN CHEMISTRY (Clean Chemistry, Atom Economy, Environmentally benign chemistry, Benign-by-design chemistry) • term given by Paul T. Anastas • developing chemical products in a safe, environmentally friendly way. • defined as “to promote innovative chemical technologies that reduce or eliminate the use or generation of hazardous substances in the design, manufacture and use of chemical products” •Reducing – -wastes -hazardous reactions -risk -energy -cost
- 4. 1. Prevention 2. Less hazardous chemical synthesis 3. Designing safer chemicals 4. Design for energy efficiency 5. Use of renewable feed stocks 6. Reduction of derivatives & use of protecting groups 7. Catalysis 8. Design for degradation 9. Real time analysis for pollution prevention 10. Inherently safer chemistry for accident prevention 11. Atom economy 12. Safer solvents and auxiliaries PRINCIPLES OF GREEN CHEMISTRY A. Ivanković, A. Dronjić, A. M. Bevanda, S. Talić. Review of 12 Principles of Green Chemistry in Practice. Int. J. Sustainable and Green Energy, 6(3), 2017,49-48.
- 5. Volatile Organic Compounds (VOCs) PROBLEMS ! REPLACED BY GREEN SOLVENTS: Environmental: Photochemical smog, ozone depletion, greenhouse effect Economic: Cost Hazards: Volatility, Toxicity, Explosive, Cancerous K. Shanab, C. Neudorfer, E. Schirmer, H. Spreitzer, Green Solvents in Organic Synthesis: An Overview, Curr.Org. Chem., 2013, 17, 1179-1187
- 6. IONIC LIQUIDS Salt in the liquid state. Ionic Liquids (ILs) consist entirely of ions and being liquid below 100°C. If they are liquid at room temperature, we call them room temperature ionic liquids (RTILs). Also known as room temperature molten salts, Fused salts, ionic fluid, liquid organic salt etc. P. P. Salvi, A Brief Account On: Ionic Liquids with its Applications, Synthesis and applications of task-specific ionic liquids (TSILs), December 2010
- 7. Structure of Ionic Liquids • Made up of ions: Organic cations & Inorganic/Organic anions • Cations are asymmetric, bulky; mostly derivatives of imidazolium, pyridinium, pyrrolidinium, ammonium, phosphonium, sulphonium, thiazolium, pyrazolium, oxazolium etc • Common anions: halides, tetrachloroaluminate, hexafluorophosphate, tetrafluoroborate (inorganic) and alkylsulfate, alkylsulfonate, p-toluene sulfonate (tosylate), trifluoroacetate (organic) etc
- 8. Types of cations & anions constituting Ionic Liquids Cations Anions D. D. Irge. Ionic Liquids: A Review on Greener Chemistry Applications, Quality Ionic Liquid Synthesis and Economical Viability in a Chemical Processes, Am. J. of Phy. Chem., 5 (3), 2016,74-79.
- 9. HISTORICAL DEVELOPMENTS • First report on Room temperature IL reported by Paul Walden in 1914 - ethylammonium nitrate, [C2H5NH3] NO3 (m.p. 12°C) • Osteryoung et al, Hussey et al worked on Organic chloride- Aluminium chloride ILs in 1970s-1980s -- First generation ILs • Wilkes and Zaworotko, 1992 reported ILs 1-ethyl-3- methyl imidazolium cation with either tetrafluoroborate or hexafluorophosphate anion --Second generation ILs • Development of Modern day ILs – tri-fluoromethane sulphonate, bis-(tri-fluoromethanesulfonyl)imide, tris- (trifluoromethanesulfonyl)methide PAUL WALDEN Mallakpour, Shadpour & Dinari, Mohamad. (2012). Ionic Liquids As Green Solvents: Progress and Prospects. 10.1007/978-94-007-2891-2_1.
- 10. SYNTHESIS OF IONIC LIQUIDS Two step synthesis: (1) The formation of the Desired Cation, (2) Anion Exchange Common alkylating agents: Methyl triflate Methyl tosylate Octyl tosylate R. Ratti, Ionic Liquids: Synthesis and Applications in Catalysis, Hindawi Pub. Corporation, Adv. in Chem., 2014, Art. ID 729842, 16
- 11. Properties of ILs that distinguishes them from other solvents 1. Zero or no vapor pressure, i.e. they do not evaporate easily 2. Non-flammable 3. High thermal stability 4. Immiscible in majority of org. solvents 5. Easily recyclable 6. have good solubility of gases 7. Large electrochemical window Other properties include: 1. Low melting point 2. Good ionic conductors 3. Viscous 4. Non-toxic since non-volatile, however causing considerable water pollution. Mallakpour, Shadpour & Dinari, Mohamad. (2012). Ionic Liquids As Green Solvents: Progress and Prospects. 10.1007/978-94-007-2891-2_1 D. D. Irge. Ionic Liquids: A Review on Greener Chemistry Applications, Quality Ionic Liquid Synthesis and Economical Viability in a Chemical Processes. American Journal of Physical Chemistry, 5(3), 2016, 74-79.
- 13. USE OF IONIC LIQUIDS IN ORGANIC SYNTHESIS & CATALYSIS AS GREEN SOLVENTS.
- 14. IONIC LIQUIDS IN DIFFERENT ORGANIC REACTIONS 1. Diels Alder Reaction • Reaction proceeds in an almost fully endo-selective manner. • Ratio of endo/exo product depends on the lewis acidity of the IL, more the acidity, more is the ratio of endo/exo product.
- 15. 2. Heck reaction • Reaction of aryl halide & styrene using Pd-catalyst in polar solvent. • If less reactive ArBr or ArCl is used, Phosphine ligand is added • In ILs as solvents, addition of ligand is not necessary; high yield
- 16. 3. Wittig Reaction •Classic problem: separation of the product and the by-product. •Separation and purification usually carried out by crystallization or chromatography. •When ionic liquid used as solvent, the product and phosphine oxide can be easily separated by combining an ether extraction and a toluene extraction after the reaction is complete. •The ionic liquid is reused.
- 17. 4. Friedal Craft acylation •Product obtained quantitatively within 1h; p-/o-product ratio of 96% •Using acetonitrile - lower conversion of 64% at 1h; reduced p-/o-product ratio 93% High yield & high selectivity
- 18. 5. Reduction ionic liquid temp. (oC) time (h) Y. (%) bmimBF4 100 16 93 emimBF4 100 16 90 emimPF6 100 16 96 emimPF6 r.t. 48 94 Reductions using simple trialkylboranes generally require reaction temperatures in excess of 150oC.
- 19. 6. Hydrogenation •Product exists in the alcoholic phase; Catalyst in the ionic liquid phase. •Separated by decantation. •Catalyst is reused without loss in activity.
- 20. 7. Stille Reactions iodocyclohexeneone vinylbutyltin •Product separation is easier •Catalyst can be reused •ionic liquid/catalyst phase is air and moisture stable
- 21. 8. Ring opening reaction • Reaction in presence of ionic liquids proceeds at room temperature to give β-aminoalcohols in high yield. • The product is extracted with ether. •Ionic liquid is reused.
- 22. VARIOUS TYPES OF IONIC LIQUIDS 1. Functional Ionic Liquid/ Task-specific ionic liquids (TSILs): • Possess functional groups covalently bonded to IL ions. • Example- IL bearing appended amines, can separate CO2 from gas streams, IL with hydroxyl groups can act as phase transfer catalyst in the synthesis of ethoxybenzene etc. 2. Deep Eutectic solvents ( DES): • Mixture of two components- a quaternary ammonium halide salt+ a hydrogen bond donor. • M.P of the mixture is less than the M.P. of the individual components. • Example- mixture of choline chloride & urea. • ease of preparation, and easy availability from relatively inexpensive components: Advantages over ILs. E.L. Smith, A. P. Abbott,, K. S. Ryder, Deep Eutectic Solvents (DESs) and Their Applications, Chem. Rev., 2014, 114 (21), 11060–11082
- 23. REFERENCES 1. A. Ivanković, A. Dronjić, A. M. Bevanda, S. Talić. Review of 12 Principles of Green Chemistry in Practice. Int. J. Sustainable and Green Energy, 6(3), 2017, 49-48. 2. K. Shanab, C. Neudorfer, E. Schirmer, H. Spreitzer, Green Solvents in Organic Synthesis: An Overview, Curr.Org. Chem., 2013, 17, 1179-1187 3. D. D. Irge. Ionic Liquids: A Review on Greener Chemistry Applications, Quality Ionic Liquid Synthesis and Economical Viability in a Chemical Processes, Am. J. of Phy. Chem., 5 (3), 2016, 74-79. 4. R. Ratti, Ionic Liquids: Synthesis and Applications in Catalysis, Hindawi Pub. Corporation, Adv. in Chem., 2014, Art. ID 729842, 16 5. Mallakpour, Shadpour & Dinari, Mohamad. (2012). Ionic Liquids As Green Solvents: Progress and Prospects. 10.1007/978-94-007-2891-2_1. 6. P. P. Salvi, A Brief Account On: Ionic Liquids with its Applications, Synthesis and applications of task-specific ionic liquids (TSILs), December 2010 7. Rekha Devi al. Ionic liquids-Useful Reaction Green Solvents for the Future (A Review) Int. J. of Recent Research Aspects ISSN: 2349-7688, 2, Issue 2, June 2015, 26-29 8. E.L. Smith, A. P. Abbott,, K. S. Ryder, Deep Eutectic Solvents (DESs) and Their Applications, Chem. Rev., 2014, 114 (21), 11060–11082
Notes de l'éditeur
- HMPA (hexamethylphosphoric triamide) are replaced by DMI (1,3-dimethyl-2- imidazolinone). Chemists should focus on using molecular level design to develop products that finally degrade into hazardless substances when released into the environment. For example, a recent study on the chemical storage of cyclopentadiene describes the need for storage under cold conditions and immediate usage. Cyclopentadiene is known to spontaneously dimerize exothermically. “atom economy” was developed by B.M. Trost of Standford University to evaluate the efficiency of chemical transformations.
- Imidazolium, pyridinium, ammonium, phosphonium, thiazolium, pyrazolium, pyrrolidinium, oxazolium, sulphonium tetrachloroaluminate, hexafluorophosphate, tetrafluoroborate (inorganic) and alkylsulfate, alkylsulfonate, p-toluene sulfonate (tosylate), trifluoroacetate (organic)
- The hygroscopic nature of AlCl3 based ILs has delayed the progress in their use in many applications since they must be prepared and handled under inert gas atmosphere. Thus, the synthesis of air and water stable ILs, which are considered as the second generation of ILs, attracted further interest in the use of ILs in various fields. these ILs are water insensitive; however, the exposure to moisture for a long time can cause some changes in their physical and chemical properties
- This step is generally followed by an acidbase neutralization or metathesis of the resulting halide salt with a Group 1A metal, ammonium, or silver salt of the desired anion to afford the IL, together with a stoichiometric amount of by-product (HX or MX, respectively) which must subsequently be removed
- They are immiscible with a number of organic solvents and provide a non-aqueous, polar alternative for two phase systems, this has been used to effect total catalyst recovery in a number of transition metal catalyzed reactions. Hydrophobic ionic liquids can also be used as immiscible polar phase with water. They have good solubility of gases, e.g. H2, CO and O2, which makes them attractive solvents for catalytic hydrogenations, carbonylations, hydroformylations, and aerobic oxidations. The increase in anion size leads to a decrease in melting point.
- . Kabalka et al. have reported this reduction using trialkylborane in which bmimBF4, emimBF4, and 1-ethyl-3-methylimidazolium hexafluorophosphate (emimPF6) are used as solvents.9a) For example, when benzaldehyde was reduced by tributylborane in emimPF6, the reaction proceeded rapidly at 100 dgreeC to give the product in high yield. Although long reaction time is needed comparatively, the product can be obtained even at room temperature.
- In the asymmetric hydrogenation of C-C double bond using homogeneous chiral transition metal complexes, the recovery of the catalyst and the seperation of the products are often troublesome. reagents are allowed to react in a two phase system of an ionic liquid and an alcohol.
- Stille reaction is a useful reaction where an organotin compound and an electrophilic reagent are reacted to form a C-C bond under mild condition in the presence of palladium catalyst. In the reaction of vinyltributyltin and iodocyclohexenone in an ionic liquid, the product can be extracted with ether and te catalyst is retained in the ionic liquid. The ionic liquid and the catalyst can be reused as they are. This ionic liquid/catalyst phase is air and moisture stable and so can be used after a long storage without loss in activity.
- As described above, a variety of reactions utilizing ionic liquids have been conducted, and the improvement of yields and the recovery and reuse of solvents have been reported. Furthermore, they are also applied to alkylations,13) allylations,14) epoxidations,15) cycloadditions,16) hydroesterifications,17) and reactions using supercritical CO2,18) in which they are reported to be effective. Ionic liquids are used not only as reaction solvents but also reported in electrochemical applications as the electrolyte of a secondary battery, due to their high ionic conductivity. Ionic liquids are attracting attention as environmentally-friendly excellent solvents, because they are safe, easy to separate and purify from the products, recyclable as solvents, and often can be reused with the catalyst.
- DESs contain large, nonsymmetric ions that have low lattice energy and hence low melting points. They are usually obtained by the complexation of a quaternary ammonium salt with a metal salt or hydrogen bond donor (HBD). The charge delocalization occurring through hydrogen bonding between for example a halide ion and the hydrogen-donor moiety is responsible for the decrease in the melting point of the mixture relative to the melting points of the individual components. These liquids were termed deep eutectic solvents to differentiate them from ionic liquids which contain only discrete anions. DESs have several advantages over traditional ILs such as their ease of preparation, and easy availability from relatively inexpensive components (the components themselves are toxicologically well-characterized, so they can be easily shipped for large scale processing); they are, however, in general less chemically inert.