Green Chemistry Blog

Researchers from Iowa State University have recently developed a route to non-solvated aluminum trihydride (alane), free of metallic aluminum. The reaction occurs at room temperature by the mechanical milling of lithium aluminum hydride and aluminum chloride and a nearly complete conversion can be achieved in 30–60 mins. The formation of aluminum can be entirely avoided above a certain critical pressure, which depends on the nature of the gas and the milling parameters. An intermediate was identified in the process, which reacts to produce alane and lithium chloride.

Due to the impractical conditions required for the direct hydrogenation of aluminum, alternative routes that allow for the large-scale preparation of alane are essential, for example the one described in this paper. The authors have also recently introduced a mechanochemical synthesis of alane using lithium hydride as a starting material, which directly leads to adduct-free alane.

Check out the original article online now:

Solvent-free mechanochemical synthesis of alane, AlH₃: effect of pressure on the reaction pathway
S. Gupta, T. Kobayashi, I. Z. Hlova, J. F. Goldston, M. Pruski, and V. K. Pecharsky
Green Chem. 2014, 16, 4378.
DOI: 10.1039/C4GC00998C

Jenna Flogeras obtained her B.Sc. and M.Sc. in Chemistry from the University of New Brunswick (Fredericton), Canada. She is currently a Ph.D. student at Memorial University in Newfoundland, where she studies aluminum-based catalysts under the supervision of Dr. Francesca Kerton.

Utilization of renewable materials, such as carbon dioxide and cellulose, is a prevailing goal of green chemistry. Homogenous conditions promote the use of cellulose, but finding solvent systems that appreciably dissolve this robust polymer is a difficult task. Processing cellulose with minimal waste and economic cost are additional considerations, and existing methods warrant improvement in these regards. In another fashion, the utilization of carbon dioxide is dependent upon novel methods for capture and storage (CCS). Researchers at the Dalian National Laboratory for Clean Energy, China, have integrated the goals of CCS and cellulose dissolution in their latest research effort.

It is well known that mixtures of organic liquids, comprised of a strong base and an alcohol, form reversible ionic compounds upon the introduction of carbon dioxide. By using 1,1,3,3-tetramethyl guanidine in combination with dimethylsulfoxide (DMSO) and ethylene glycol, in particular, they observed microcrystalline cellulose dissolution of up to 10 wt% under mild conditions. The presence of the co-solvent DMSO was integral to achieve this extent of dissolution, and cellulose regeneration and recovery could be accomplished by several methods.

Learn more about their exciting results here:

Capturing CO₂ for cellulose dissolution
Haibo Xie, Xue Yu, Yunlong Yang, and Zongbao Kent Zhao
Green Chem., 2014, Advance Article, DOI: 10.1039/C3GC42395F 
 

Jenna Flogeras obtained her B.Sc. and M.Sc. in Chemistry from the University of New Brunswick (Fredericton), Canada. She is currently working towards her Ph.D. at Memorial University of Newfoundland, under the supervision of Dr. Francesca Kerton. Her research is focused on the synthesis of biodegradable polymers using main-group metal complexes as catalysts.

Chitin is a main constituent of the exoskeletons of insects and crustaceans. Utilizing this biopolymer in the production of value-added chemicals, particularly nitrogen-containing aromatic compounds (e.g., furans), is a more sustainable route than their energy-intensive synthesis from ammonia. Chitin may be subjected to hydrolysis reactions to produce N-acetyl-D-glucosamine (NAG), its monomeric constituent. Kerton et al. previously reported a high-yielding synthesis of 3-acetamido-5-acetylfuran (3A5AF) by the direct dehydration of NAG. In this paper, Kerton and researchers from the National University of Singapore aimed to combine the two steps to generate NAG in situ from chitin and convert it to 3A5AF.

In order to dissolve chitin, its extensive hydrogen-bonding network must be tempered. The use of polar, aprotic solvents in combination with metal salts can accomplish this challenging task, enabling the dehydration reaction to occur more easily. Chloride-containing salts or additives also facilitate the reaction, which is suspected to occur through their disruptive effect on the hydrogen bonds. Dual or tri-component additive systems of boric acid with alkali or alkaline earth metal chlorides resulted in the highest yields of 3A5AF. The optimized conditions used boric acid and sodium chloride in NMP (N-methyl-2-pyrrolidone) to give ca. 7.5% 3A5AF, while 50% chitin conversion was achieved, representing an array of other products. Pre-treatment of chitin to initiate the depolymerisation was suggested as a potential means to increase 3A5AF yields.

Read this article now, we’ve made it free to access until 3rd March:

Direct conversion of chitin into a N-containing furan derivative
Xi Chen, Shu Ling Chew, Francesca M. Kerton, and Ning Yan
Green Chem., 2014, Advance Article, DOI: 10.1039/C3GC42436G

Jenna Flogeras obtained her B.Sc. and M.Sc. in Chemistry from the University of New Brunswick (Fredericton), Canada. She is currently working towards her Ph.D. at Memorial University of Newfoundland, under the supervision of Dr. Francesca Kerton. Her research is focused on the synthesis of biodegradable polymers using main-group metal complexes as catalysts.