Green Chemistry Blog

Philip Jessop and co-workers report tertiary amine solvents with switchable-hydrophilicity which have been applied to recycling polystyrene foam.

These switchable-hydrophilicity solvents (SHS) have very low miscibility with water and air, but are completely miscible in the presence of a CO₂ atmosphere.  Jessop and his team had previously reported using N,N,N’-tributylpentanamidine as a SHS which could easily be removed from organic products.  However, N,N,N’-tributylpentanamidine is very difficult to synthesise and is not commercially available.

In this work, Jessop reports the use of several tertiary amines which are either commercially available or easily prepared.  As well as investigating the factors which affect the rate of switching, the group also applied one of the amines studied to the recycling of polystyrene foam.  The polystyrene foam was dissolved in one of the SHSs, and after addition of carbonated water formed dense polystyrene.  In future, this could potentially make the transportation and recycling of polystyrene foam waste less energy intensive and more efficient.

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Tertiary amine solvents having switchable hydrophilicity

Philip G. Jessop, Lisa Kozycz, Zahra Ghoshouni Rahami, Dylan Schoenmakers, Alaina R. Boyd, Dominik Wechsler and Amy M. Holland, Green Chem., 2011, DOI: 10.1039/C0GC00806K

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A solvent having switchable hydrophilicity
Philip G. Jessop, Lam Phan, Andrew Carrier, Shona Robinson, Christoph J. Dürr and Jitendra R. Harjani, Green Chem., 2010, 12, 809-814
DOI: 10.1039/B926885E

Beckman and Munshi reports a reversible CO₂ carrier (RCC) for the carboxylation of ketone to β-ketoester under ambient CO₂ pressure and temperature.

RCC has been synthesized by immobilizing 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) on methylhydrosiloxane support and reacting with CO₂ with 100% degree of functionalisation. RCC is found to be recyclable and shows retention of activity in 5 recycles. CO₂ absorption under ambient temperature and desorption at 120 °C renders the material suitable for carrying out carboxylation reactions at 25 °C with excellent yields. The yield of the reaction can reach up to 100% with TON 200 in 4 h. The extent of the reaction primarily depends upon enol content of the substrate. β-Ketoacid produced during the reaction can be isolated and converted to its corresponding methyl ester derivative by reacting with methyl iodide.

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Ambient carboxylation on a supported reversible CO₂ carrier: ketone to β-keto ester, Eric J. Beckman and Pradip Munshi, Green Chem., 2011, DOI: 10.1039/C0GC00704H, Advanced Article, Paper

Righi and co-workers here present the life cycle assessment (LCA) of cellulose dissolution with ionic liquids 1-butyl-3-methylimidazolium chloride (Bmim Cl). The authors compared the “greenness” of the process with the well established environmental friendly N-methyl-morpholine-N-oxide (NMMO)/H2O process. Results from the LCA suggest that both processes are comparable.

Specifically, the process with Bmim Cl generates a higher environmental load on abiotic resource depletion, emissions of volatile organic compounds and ecotoxicity than the NMMO/H2O process. Conversely it has some environmental advantages with regards to human toxicity. In both cellulose dissolution processes, the major contributions to the environmental impacts come from precursor syntheses.

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Comparative cradle-to-gate life cycle assessments of cellulose dissolution with 1-butyl-3-methylimidazolium chloride and N-methyl-morpholine-N-oxide

Serena Righi, Andrea Morfino, Paola Galletti, Chiara Samorì, Alessandro Tugnoli and Carlo Stramigioli
Green Chem., 2011, DOI: 10.1039/C0GC00647E, Paper

Spanish scientists have devised a greener form of liquid chromatography by using cyclodextrins as additives in the mobile phase. This results in more water being used in the chromatographic process.

Using cyclodextrins in chromatography could increase the amount of water being used

Cyclodextrins are a natural, renewable compound made from starch and are totally biodegradable. They can be modified and tailor made, and as a result are used in a variety of fields including the pharmaceutical, food and cosmetic industries.

High performance liquid chromatography (HPLC) is a commonly used analytical technique that allows fast separation and quantification of compounds in complex mixtures. Owing to its high resolution and sensitivity, it is widely employed in academic and industrial settings.

Using cyclodextrins in chromatography could increase the amount of water being used
Antonia Martin and colleagues from the Complutense University of Madrid investigated ways of reducing the amount of acetonitrile and developing chromatographic methods that use an increasing amount of water and renewable solvents like ethanol. ‘Due to the toxicity of acetonitrile, these mobile phases have to be treated as chemical waste, so we were interested in using non-toxic solvents, especially alcohols, as an alternative,’ says Martin.

Being greener is only a benefit if the performance of the new system is comparable to current methods. To check this, Martin and her team tested for beta-carbolines, a naturally occurring alkaloid linked to neurological diseases, in human blood serum. The results were as good as non-cyclodextrin modified HPLC in terms of accuracy – in fact the cyclodextrins increased the detection sensitivity.

‘There was a rapid increase in the price of acetonitrile during 2008 so these substitutions will lead to significant cost benefits as well as green chemistry benefits,’ he adds.

Rebecca Brodie

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Eco-friendly liquid chromatographic separations based on the use of cyclodextrins as mobile phase additives
Víctor González-Ruiz, Andrés G. León, Ana I. Olives, M. Antonia Martín and J. Carlos Menéndez, Green Chem., 2011, DOI:10.1039/c0gc00456a

The following hot articles can be freely downloaded until Christmas after a simple registration process: http://pubs.rsc.org/en/account/register

Mechanism of efficient anti-Markovnikov olefin hydroarylation catalyzed by homogeneous Ir(III) complexes
Elucidation of the full mechanism of the hydroarylation reaction between unactivated olefins and benzene carried out by the (acac-O,O)Ir^III(R)(L) catalyst.

Gaurav Bhalla, Steven M. Bischof, Somesh K. Ganesh, Xiang Yang Liu, C. J. Jones, Andrey Borzenko, William J. Tenn, III, Daniel H. Ess, Brian G. Hashiguchi, Kapil S. Lokare, Chin Hin Leung, Jonas Oxgaard, William A. Goddard, III and

Roy A. Periana, Green Chem., 2011, Advance Article, DOI:10.1039/C0GC00330A

Renewable gasoline from aqueous phase hydrodeoxygenation of aqueous sugar solutions prepared by hydrolysis of maple wood

A renewable gasoline can be prepared directly from biomass sugar solutions in a two-bed reactor system.

Ning Li, Geoffrey A. Tompsett, Taiying Zhang, Jian Shi, Charles E. Wyman and George W. Huber, Green Chem., 2011, Advance Article, DOI: 10.1039/C0GC00501K 

Challenges for recycling ionic liquids by using pressure driven membrane processes

Recycling of hydrophilic, water miscible ionic liquids/deep eutectic solvents by means of pressure driven membrane separation technologies was critically studied.

Kurt Haerens, Stephanie Van Deuren, Edward Matthijs and Bart Van der Bruggen, Green Chem., 2010, 12, 2182-2188, DOI: 10.1039/C0GC00406E

Ionic liquid solvent properties as predictors of lignocellulose pretreatment efficacy

Room temperature ionic liquids containing [OAc⁻] anions, with high Kamlett–Taft β parameter values (β 〉 1), are effective solvents for pretreatment of recalcitrant maple wood flour.

Thomas V. Doherty, Mauricio Mora-Pale, Sage E. Foley, Robert J. Linhardt and Jonathan S. Dordick, Green Chem., 2010, 12, 1967-1975, DOI: 10.1039/C0GC00206B

Top most cited articles in 2010 published in Green Chemistry:

German scientists have developed a model to predict the solubility of cellulose in different ionic liquids. 

In the past, ionic liquids have been shown to be promising solvents for cellulose but have you ever wondered which ones to use because the ionic liquid candidates are numerous? Kai Leonhard and co-workers, at the RWTH Aachen University in Germany, used a computing model called COSMO-RS to screen over 2000 ionic liquids with respect to their dissolving power for cellulose. The results are in good agreement with experimental data available in literature. 

Leonhard and his team found that “anions were mainly responsible for the respective dissolving power, suggesting some new ionic liquids as potential candidates for cellulose dissolution”. 

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Modelling cellulose solubilities in ionic liquids using COSMO-RS
Jens Kahlen, Kai Masuch and Kai Leonhard, Green Chem., 2010, DOI: 10.1039/C0GC00200C, Paper

“This is the first demonstration of electrochemical hydrogenolysis,” says Richard G. Compton and co-workers.

The UK scientists at Oxford University showed a simple and rapid electrochemical hydrogenolysis process in room temperature ionic liquid requiring no hydrogen gas. 

Hydrogenolysis of N,N¢-bis(benzyloxycarbonyl)-L-lysine was achieved by the electrochemical reduction of a labile proton at a Pd microelectrode,and the hydrogenolysis monitored by the size of the Pd/H oxidation peak. “The extension of this system to hydrogenation reactions should present no great problems, ” claims Compton and co-workers.

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Hydrogenolysis without hydrogen gas: hydrogen loaded palladium electrodes by electrolysis of H[NTf2] in a room temperature ionic liquid

Yao Meng, Leigh Aldous and Richard G. Compton, Green Chem., 2010, DOI: 10.1039/C0GC00450B

Nishide and Heard reports a novel recyclable acid catalysts for use in esterification, Friedel-Crafts acylation and other condensation reactions. The team from Waseda University in Japan and Monash University in Australia reports the synthesis of high-density poly(vinylsolfonic acid)-grafted solid acid materials with extremely high acid dissociation abilities.

They found the catalyst to possess interesting anti-corrosive properties implying that reactor corrosion is minimised. The process introduces “a new avenue to carry out such solid-phase acid catalysed synthetic reactions in a more benign, green chemical manner, whilst minimizing pollution/contamination risks due to leading to minimum risks of reactant contamination due to corrosion”, claims Hearn and co-workers.

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Poly(vinylsulfonic acid)-grafted solid catalysts: new materials for acid-catalysed organic synthetic reactions

Teruyuki Okayasu, Kei Saito, Hiroyuki Nishide and Milton T. W. Hearn, Green Chem., 2010, DOI:10.1039/C0GC00241K