Renewable solvents

As already noted by Verkuijlen and Boelhouwer in 1974 [29], the SM of highly unsaturated fatty esters produces, among other compounds, considerable amounts of 1,4-cyclohexadiene (1,4-CHD). This fact has been exploited by Mathers et al. for the production of 1,3-cyclohexadiene (1,3-CHD) via metathesis and isomerization reactions of plant oils [141]. For instance, 1,4-CHD was obtained by treatment of soybean oil with C4 and was subsequently isomerized with RuHCl(CO)(PPh3)3. Then, the produced 1,3-CHD was polymerized with nickel(II)acetylacetonate/ methaluminoxane. Interestingly, the polymerizations could be carried out in bulk and using hydrogenated D-limonene as renewable solvent. The polymers thus obtained presented / m around 300°C. 

Turley, D.B., F.J. Areal and J.E. Copeland, The Opportunities for Use of Esters ofRapeseed Oil as Bio-Renewable Solvents, HGCA Research Review 52, Home-Grown Cereals Authority, London (2004). 

D-Limonene and ot-pinene have been used as renewable solvents and chain transfer agents in metallocene-methylaluminoxane (MAO) catalysed polymerization of ot-olefins. Chain transfer from the catalyst to the solvent reduces the achieved in limonene compared with toluene and also reduces the overall catalyst activity. This was confirmed, as in the ROMP studies, by performing identical reactions in hydrogenated limonene. However, an increase in stereospecificity was seen when D-limonene was used as the solvent. This is measured as the mole fraction of [mmmm] pentads seen in NMR spectra of the polymer. 100% isotactic polypropylene would give a value of 1.0. On performing the same propylene polymerization reactions in toluene and then in limonene, the mole fraction of [mmmm] pentads increased from 0.86 to 0.94, indicating that using a chiral solvent influences the outcome of stereospecific polymerizations. Unfortunately, when a-pinene was used, some poly(a-pinene) was found to form and this contaminates the main polymer product. 

Hron, R.J. Renewable solvents for vegetable oil extraction, /. Am. Oil Chem. Soc. 1982, 59, 674A-684A. 

The ABE fermentation process was first developed by C. Weizmann at Manchester University in 1912. Commercial production quickly spread to the United States and then worldwide during the First and Second World Wars first to produce acetone for ammunitions and then later to produce butanol for paint lacquers. The fermentation process fell out of favor in the United States and Europe in the 1950s when renewable solvents could no longer compete with their synthetic equivalents on price. Some production, via fermentation, continued in China, Russia, and South Africa until the early 1980s [54]. 

Chapter 3 Renewable Solvent Selection in Medicinal Chemistiy... 

Perhaps the biggest impact will be over the use of solvents since many of the more common organic solvents are under threat from REACH these include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF) and dime-thylacetamide (DMAc). (For more information on solvent substitution guides see Chapter 2, Tools for Facilitating more Sustainable Medicinal Chemistiy , by Helen Sneddon and James Sherwood s Chapter 3 on renewable solvent selection.) The electronics industry has also been subject to chemical legislation that aims to replace especially hazardous substances. RoHS (restriction on hazardous substances) targets certain chemicals, including lead, mercuiy, cadmium chromates and polybrominated flame retardants. ... 

Another example of a successful renewable solvent that is not a fermentation product is 2-methyltetrahydrofuran (2-MeTHF). It is commercially synthesised by the acid mediated dehydration of hemicellulose into furfural, which is followed by a hydrogenation. Although similar to tetrahydrofuran (THF), the most obvious candidate for substitution by 2-MeTHF, it is a distinct molecule made by a process that has no equivalent downstream of the oil refinery where THF originates. Peroxide formation issues are unresolved, but 2-MeTHF does have advantages over THF. 2-Methyltetrahydrofuran is less water soluble than THF, and the achievable concentration of organometallic substrates is greater in 2-MeTHF than it is in THF. ... 

Choice of more benign solvents may also result in easier work-ups, and will certainly be greener (see also Chapters 2 Tools for Facilitating More Sustainable Medicinal Chemistry and 3 Renewable Solvent Selection in Medicinal Chemistry )... 

The interesting aspect of this two-bond-forming reaction is the simplicity of its use. The reaction proceeds effortlessly in 18 h under oxygen atmosphere (1 atm), using the relatively inexpensive Pd(OAc)2 (1 mol%) in a renewable solvent (MeTHF) without the need for ligands or bases. The broad range of accepted substrates allow the synthesis of amino-substituted imidazopyridines, benzoxazoles,... 

One of the largest areas of consumption of petroleum-based chemicals in a conventional chemical transformation are solvents used as reaction media (i.e., solvents account for 80-90% of mass utilization in a typical phannaceutical/fine chemical operational process). Thus, solvents are responsible for most of the waste generated in the chemical industries and laboratories. In this sense, and to face the diminution of oil supplies, there has been a global demand for the development of renewable solvents that are not based on crude petroleum. On the other hand, conventional volatile organic solvents (VOCs) commonly used as reaction media can cause well-estabhshed environmental problems due to their ... 

The developments and introduction of new solvents are discussed in Chapter 20 (supercritical fluids, ionic liquids, deep eutectic solvents, and renewable solvents) and in Chapter 3. These generic groups of materials are emerging technologies studied to address environmental concerns. 

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