Green Chemistry Blog

Hydrolytic hydrogenation of cellulose with hydrotreated caesium salts of heteropoly acids and Ru/C.  Hydrolysis of cellulose by an acid catalyst, followed by metal-catalysed hydrogenation gives hexitols, which can be used as renewable chemicals and fuels.  In this study the authors use a combined catalyst of caesium salts of heteropoly acids (HPAs) and Ru/C.  Although HPAs have been used before, they cannot be recovered from the reaction afterwards, which greatly limits their use in industrial processes.

However, in this work Sels and co-workers have found that the caesium salts of HPAs are not only highly selective (giving up to 90% yields of hexitols) and can be performed under mild reaction conditions, the Cs HPA salts could be recovered by simple recrystallisation at room temperature without using organic solvents. (Green Chem., 2011, DOI: 10.1039/c1gc15350a)

Selective oxidation of 5-hydroxymethyl-2-furfural using supported gold-copper nanoparticles. 5-Hydroxymethyl-2-furfural (HMF), formed from the dehydration of sugars, can be oxidised to 2,5-furandicarboxylic acid (FDCA), which recently has been suggested as a substitute for terephthalate acid – the monomer for the production of terephthalate plastic. However, currently many strategies to oxidise HMF to FDCA have various drawbacks, including the use of stoichiometric oxidants. 

In this work Hutchings and colleagues report the use of gold-copper supported nanoparticles as an effective catalyst for the oxidation of HMF to FDCA.  Although supported gold nanoparticles have been applied to this reaction previously, catalyst stability has remained very low. However, the bimetallic nanoparticles reported here, supported on titania, exhibit a remarkable degree of stability, even in the presence of base.  The catalyst could be recovered by filtration and reused several times without significant loss of activity. (Green Chem., 2011, DOI: c1gc15355b)

Scientists from Sweden, Egypt, Denmark and India have collaborated to develop a computational tool to assess the greenness of high performance liquid chromatography (HPLC) methods.

This environmental assessment tool (EAT) takes into account the safety, environmental and health issues for all solvents involved or used in the chromatographic method.  A total score is then calculated that can be used to compare the greenness of various HPLC methods.  Although other tools have been developed to try and evaluate the green aspect of these methods, they often do not provide a sufficiently quantitative result for comparison between various methods and are not always user-friendly or widely accessible.

The HPLC-EAT software can be downloaded free of charge at http://www.biotek.lu.se/hplc-eat/ and can also be combined with another free software eco-solvent tool to perform life cycle assessments of waste disposal options (such as distillation or incineration).

Click the link below to find out more! Read the full text for free until 22 July

Energy & environment: Free environmental assessment for liquid chromatography solvents, Y Gaber, U Tornvall, M A Kumar, M A Amin and R Hatti-Kaul, Green Chem., 2011, DOI: 10.1039/c0gc00667j

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Expanding GSK’s solvent selection guide – embedding sustainability into solvent selection starting at medicinal chemistry, Richard K. Henderson, Concepción Jiménez-González, David J. C. Constable, Sarah R. Alston, Graham G. A. Inglis, Gail Fisher, James Sherwood, Steve P. Binks and Alan D. Curzons, Green Chem., 2011, 13, 854-862 DOI: 10.1039/C0GC00918K

 Polyamides have been decomposed to ω-hydroxyalkanoic acid derivatives – important intermediates in the chemical industry – using supercritical methanol.  This is one of the first methods for economical upgrading of polymers through the depolymerisation process.

Akio Kamimura and colleagues from Yamaguchi University and UIbe Industries Ltd., Japan, have developed a method to convert polyamides to valuable chemicals.  Currently, recycling of plastics commonly involves converting the polymers back to their monomers. However, these methods are not always economically viable because they are often more expensive than other ways of treating waste plastics.  By converting polymers to valuable chemicals, this would make polymer recycling a more attractive route and solve some of the economic problems. 

In this study, by using supercritical methanol, Kamimura converted nylon-6 selectively to two valuable compounds – methyl 6-hydroxycapronate and methyl 5-hexenoate. Given that the average price for these ω-hydroxyalkanoic acid derivatives is about 6-7 times higher (per kg, based on 2008 figures) than the monomer (caprolactam), Kamimura believes that this method will open up new avenues in the development of plastics recycling.

To read more, please click the link below!  Full text Free until 20th July.

Direct conversion of polyamides to ω-hydroxyalkanoic acid derivatives by using supercritical MeOH, Akio Kamimura, Kouji Kaiso, Shuzo Suzuki, Yusuke Oishi, Yuki Ohara, Tsunemi Sugimoto, Kohichi Kashiwagi and Makoto Yoshimoto, Green Chem., 2011, DOI: 10.1039/C1GC15172J

A new method has been developed to synthesis spiro-substituted benzo[b]furo[3,4-e][1,4]diazepene derivatives in one step, forming two spiro rings and five σ bonds in the process.

This chemo- and regioselective [4+2+1] domino cyclization reaction was discovered by scientists from Xuzhou Normal University, China and Texas Tech University, USA.  The synthesis of  heterocyclic compounds with quaternary carbon centres is important as these compounds are useful intermediates in organic synthesis and are often biologically active. 

The procedure developed here is performed in water with microwave irradiation and uses easily available and cheap starting materials.  This one-pot reaction can be performed in 10-18 minutes with reduced waste production and without the use of any strong acids or metal promoters.  In addition, recrystallization and chromatography purification procedures can be avoided as the pure products can be obtained by simply washing the crude product with 95% ethanol.

The authors feel this will serve as a nice addition to Group-Assistant Purification chemistry.

Click the link below to read more! Full text free until 18th July.

[4+2+1] Domino cyclization in water for chemo- and regioselective synthesis of spiro-substituted benzo[b]furo[3,4-e][1,4]diazepine derivatives, Chuang Cheng, Bo Jiang, Shu-Jiang Tu and Guigen Li, Green Chem., 2011, DOI: 10.1039/C1GC15183E