Project 25-1_093112 problem project.pptx

It is end semester project

1. “ IONIC LIQUIDS AS SUSTAINABLE SOLVENT FOR ORGANIC SYNTHESIS” S ubmi tted in the fulfillment of the requirement for the award of Degree in BACHELOR OF SCIENCE IN CHEMISTRY under Dibrugarh University Debraj Roy College (Autonomous), Golaghat , Assam Department of Chemistry A Project Seminar on Submitted by- Mayuri Baruah Pranay Jyoti Dutta Raj Protim Autriya Shilpi Bormudoi Uttara Tongla Under the Guidance of - Prof. Bedanta Kumar Bora Dean Of Science & HOD Department of Chemistry Debraj Roy College (Autonomous)

2. Acknowledgement We would like to express our sincere gratitude to Mr. Bedanta Kumar Bora, Professor and Head of the Department of Chemistry, Debraj Roy College (Autonomous), Golaghat , for his invaluable guidance and encouragement throughout the preparation of this seminar. His insightful suggestions and continuous support have been instrumental in shaping our understanding of this topic.

3. Contents 6. References

4. 1. Introduction to Ionic Liquids: Unique Properties and Classification Definition Salts liquid at or near room temperature Properties Low volatility, thermal stability, ionic conductivity

5. Objectives: The main aim of this project is to study how ionic liquids (ILs) can be used as safe and eco-friendly alternatives to regular solvents in organic chemistry. It focuses on: 1. Learning about the types and properties of ionic liquids. 2. Understanding how basic ionic liquids help in chemical reactions. 3. Exploring their benefits, like being reusable and less harmful. 4. Looking into new methods to make them more stable and useful for industries. 5. Finding out their future potential and challenges in green chemistry.

6. 2. Classification of Ionic Liquids :

7. 3. Applications of Basic Ionic Liquids in Organic Synthesis : 3.1 Homogeneous Basic Ionic Liquids: Catalyzing Organic Reactions Uniform Phase : They dissolve completely in reaction mixtures. Catalytic Role : Enhance reaction rates by providing ionic basic environments. Advantages : Recyclable, selective, and environmentally friendly. The reactions catalyzed by Homogeneous Basic Ionic Liquids include Knoevenagel and Aldol Condensation, Esterification, Metal Catalyzed reactions, etc.

8. Knoevenagel Reaction : A Knoevenagel condensation involves the reaction between an aryl aldehyde and a reagent with acidic hydrogens in the presence of a base, leading to α,β-unsaturated compounds with the elimination of water. Reaction times ranged from 20 minutes to 24 hours, and the conversion yields varied between 12% and 91%. Strongly basic ionic liquids yielded higher product amounts in shorter times compared to weaker bases. The universal indicator confirmed reduced basicity of ionic liquids relative to free Hunig’s base, although [BMIM][ NTf ₂] still gave quantitative conversion. Unlike Hunig’s base, the ionic liquid could be recovered after reaction by extraction, improving reusability.

9. Fig. 1 The synthesis of Hunig’s base containing ionic liquids

10. Design and Role of DABCO-Based Ionic Liquids: Ionic liquids derived from DABCO, such as [C₂DABCO][ NTf ₂], are formed by alkylating one nitrogen of DABCO, leaving the other nitrogen as a basic site. These ionic liquids demonstrated good thermal and electrochemical stability, though their basicity was lower than pure DABCO. Using 15 mol% of [C₄DABCO][BF₄] in water resulted in a 100% yield of the Knoevenagel condensation of malononitrile and benzaldehyde within 1 minute at room temperature. The product precipitated out, while the ionic liquid remained in solution, allowing for easy recovery by filtration. The catalytic system remained effective for at least 5 cycles, with the second reaction giving 95% yield. Strongly basic ionic liquids can be made using Brønsted basic anions but often suffer from low stability due to cation degradation.

11. Fig. 2 The structure of [C 2 DABCO][NTf 2 ] (a) and [C 4 DABCO][BF 4 ] (b)

12. Binary Alkoxide Ionic Liquids: Binary ionic liquids were created using a pyrrolidinium cation and an alkoxide anion (iso- propoxide ) combined with the neutral anion [ NTf ₂] to stabilize the system. Basicity was evaluated using the inverse Hammett method, and the ionic liquids showed stability for at least 8 months under ambient conditions. These binary ionic liquids catalyzed both Knoevenagel and aldol condensations effectively. When 1 mol% of the binary ionic liquid [ Pyrr ₁,₄][ NTf ₂]₀.₅₈[ OiPr ]₀.₄₂ was used in the Knoevenagel condensation, yields improved with higher alkoxide content, ranging from 24% to 89%. The optimized catalyst ([ Pyrr ₁,₄][ NTf ₂]₀.₅₈[ OiPr ]₀.₄₂) matched the activity of pyridine, a traditional Knoevenagel base catalyst.

13. Fig.3 The structure of binary alkoxide ionic liquids ([Pyrr 1,4 ][NTf 2 ] x [O i Pr ] 1−x ).  

14. Aldol Condensation Aldehydes containing α-hydrogens can undergo self-condensation reactions when heated in the presence of a dilute or mild base.This reaction typically produces β-hydroxy aldehydes, also known as aldols, with aqueous sodium hydroxide (NaOH) being commonly used at temperatures around 70–72°C.Traditional aldol condensation methods can lead to practical issues such as reactor corrosion and the generation of inorganic salt waste. Use of Binary Alkoxide Ionic Liquids : A newer and greener approach involves using binary alkoxide ionic liquids with the general formula [ Pyrr ₁,₄][ NTf ₂]ₓ[Oi- Pr ]₁₋ₓ. These ionic liquids have been successfully used to catalyze aldol condensation reactions between acetone and benzaldehyde. The system is designed to mimic the condensation of furfural with acetone, a key reaction in converting lignin and cellulose into value-added chemical products.

15. Fig. 4 The aldol reaction catalysed by binary alkoxide ionic liquids .

16. Performance and Yields : The best-performing ionic liquid identified in the study was [ Pyrr ₁,₄][ NTf ₂]₀.₅₇[Oi- Pr ]₀.₄₃.This system achieved a 75% yield in aldol condensation, which is higher than the 69% yield obtained using conventional NaOH. The overall yield of the process was significantly improved from 12% to 75% by using the ionic liquid. Further Applications by Gao et al . Gao and colleagues synthesized similar ionic liquid systems for use in aqueous aldol condensation reactions. Their work led to the successful production of α,α′-unsaturated ketones and α,β-unsaturated aldehydes. These products are valuable intermediates in the synthesis of natural products and pharmaceutical compounds. For many substrates tested, yields exceeding 90% were achieved, showing high efficiency and applicability.

17. Fig. 5 The Aldol synthesis of α,α′-unsaturated ketones (a) and α,β-unsaturated ketones (b) catalised by basic ionic liquids.

18. Metal Catalyzed Reactions Enhanced by Basic Ionic Liquids :

19. Trihexyl tetradecylphosphonium hydroxide is more stable , making it useful for cross-coupling reactions. It is used as a basic promoter to prevent decomposition and salt build-up in flow reactions. Methanol (MeOH) interacts with protons more than , reducing unwanted cation attacks. This ionic liquid reduces salt build-up during chloride exchange reactions. When used as a base and solvent in batch Buchwald–Hartwig reactions, yields reached 44%; Suzuki– Miyaura reactions achieved 56%.

20. Fig. 6 An example of a Buchwald–Hartwig cross-coupling promoted by [P 6,6,6,14 ][OH]·4MeOH. XPhos is 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl.  

21. Esterification Han and coworkers synthesized monoacylglycerol using triacylglycerol and glycerol, where soybean oil was chosen as the source of triacylglycerol. The ionic liquid [EMIM][ OAc ] (1-ethyl-3-methylimidazolium acetate) was used both as the solvent and the catalyst in the reaction. Reaction Conditions and Results: The reaction was carried out at 80°C for 12 hours. A 94% yield was obtained in the self-esterification of benzyl alcohol. In cross-esterification reactions involving various benzylic and aliphatic alcohols, yields ranging from 70% to 94% were achieved.

22. Fig. 7 (a) Hydrogen bonding between [EMIM][ OAc ] and an alcohol substrate. (b) Activation of an aldehyde by an NHC formed from [EMIM][ OAc ] leading to esterification.

23. 3.2 Heterogenous Basic Ionic Liquids: A Sustainable Approach

24. A. Supported Ionic Liquid Phase (SILPs) SILP is formed via impregnation or tethering of ionic liquids to a porous support. They reduce the amount of ionic liquid required for a reaction as only a thin layer is used. It offers high activity and viscosity problems encounter in bulk ionic liquids are reduced to small diffusion offered to substrate and products.

25. Use of SILP: Biodiesel Synthesis Xie. et. tethered different amounts of a triazolium hydroxide ionic liquid to mesoporous SBA-15. SILPs was used to catalyze production of biodiesel from soybean oil by catalyzing transesterification with methanol to generate fatty acid methyl ester (FAME). Catalytic activity increased with SILP basicity. Highest conversion was 95% after 8 h at 65°C. SILP could be recovered and reused but the activity decreased. Catalytic recycling can be improved when the support material protects the ionic liquid

26. Disadvantage: Despite the good activity and low levels of degradation there are two main disadvantages associated with SILP:- Forces of attraction between the support surface and the ions tend to be to weak to prevent leaching to a liquid reactant phase and therefore tethering is necessary. Extra chemical steps required to tether ions increases costs.

27. B. Ionic Liquid Gel Catalysis Gels comprise a liquid phase entrapped within a solid matrix. Forces of attraction between the liquid and matrix in a gel are higher than in surface adsorption and therefore entrapment of an ionic liquid within gel does not require covalent tethering. Despite widespread use of ionic liquid to form gels there are very few examples of basic ionic liquids. The main reason for this is – instability of basic ionic liquids and relative speed of base catalyzed sol-gel process. Marr and co workers employed the binary approach to stabilize the basic ionic liquid gels and enable catalytic applications of basic ionic liquid gels.

28. Use of Ionic Liquid Gel Catalysis: Water Remediation Fe-TAML, a biomimetic peroxide activator, was incorporated within a basic IL gel for water purification. In presence of H 2 O 2 the materials acted as a heterogenous catalyst for the oxidation of dyes in aqueous solution Gels could be recovered by filtration and reused with similar activity for atleast a further four cycles A filtration test and ICP analysis of the reaction solution found no Fe leaching had occurred from gels

29. 4. Future Aspects: The Promise of Basic Ionic Liquids

30. 5. Conclusion Basic ionic liquids (BILs) catalyze various organic reactions and are being explored for sustainable applications like biofuel production and water remediation. Though they are safer than traditional bases, they are costlier and require improvements in stability and recyclability for industrial use. Molecular design has led to more stable BILs, and their performance can be enhanced by supporting them on solid materials (e.g., silica, microcapsules). Heterogenization also opens up opportunities for advanced catalytic systems. Combining stable BILs with suitable supports could soon lead to viable industrial applications.

31. 6. References Shen, J., Wang, H., Liu, H., Sun, Y., & Liu, Z. (2008).  Journal of Molecular Catalysis A: Chemical ,  280 (1-2), 24-28. Bora, D. B., & Borah, R. (2020). Sukanya Das, Niharika Kashyap, Sangeeta Kalita.  Advances in Physical Organic Chemistry ,  54 , 1 Fei, Z., Geldbach , T. J., Zhao, D., & Dyson, P. J. (2006).  Chemistry–A European Journal ,  12 (8), 2122-2130. Das, S., Dutta, T., & Borah, R. (2019).  Journal of Molecular Liquids ,  289 , 111099. Seki, S., Kobayashi, Y., Miyashiro, H., Ohno, Y., Usami, A., Mita, Y., ... & Terada, N. (2006).  Chemical Communications , (5), 544-545. Walden, P. (1914).  Bull. Acad. Imper. Sci,(St. Petersburg) ,  1800 . Hurley, F. H., & Wier, T. P. (1951).  Journal of The Electrochemical Society ,  98 (5), 203. Srivastava, N., & Banik, B. K. (2003).  The Journal of organic chemistry ,  68 (6), 2109-2114. Das, S., Kashyap, N., Kalita, S., Bora, D. B., & Borah, R. (2020).  Advances in Physical Organic Chemistry ,  54 , 1-98. Liu, Z., Xu, C., & Huang, C. (2007).  U.S. Patent No. 7,285,698 . Washington, DC: U.S. Patent and Trademark Office.

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