Renewable molecular solvents

Renewed interest in this method came recently from its adaptation to the immobilization of water/ organic solvent biphasic catalysts, resulting in the so-called supported aqueous phase catalysts (SAPCs).117 The molecular catalyst is immobilized via water, which is hydrogen bonded to the surface silanol groups reactants and products are in the organic phase (Figure 11)... 

Vegetable oils represent only 5% of the renewable resources available. Today, vegetable oils currently provide a marginal carbon feedstock contribution to the chemical industry in such applications as solvents, surfactants, and lubricants. Vegetable oils may, however, play a much more important role in the future. They are mixtures of fatty acid trigclycerides whose typical molecular structures are given in Figure 10.12. 

Further well-known molecular liquids that have recently found renewed interest as solvents for many applications are water and perfluorohydrocarbons. These occupy the two extreme positions on empirical solvent polarity scales, with water being the most polar solvent and perfluorohydrocarbons being among the least polar of solvents cf. Chapter 7). 

In recent years there has been a renewed interest in methods combining QM calculations with simulation procedures. The subject deserves a scrutiny more detailed than that we gave in introducing Warshel s LD method (Warshel and Levitt, 1976). In these methods Molecular Mechanics-type (MM) potential functions are used to describe both solute-solvent and solvent-solvent interactions, while interactions within the solute are described at the QM level. 

Proteins are routinely separated from low-molecular-weight impurities by dialysis. When a dialysis bag containing a cell extract is suspended in water or a buffered solution, small molecules pass out through the membrane s pores. If the solvent outside the bag is continually renewed, all low-molecular-weight impurities are removed from the inside. 

The metal-catalyzed oxidation of carbohydrates with molecular oxygen is a remarkable example of green chemistry because reactants are obtained from renewable resources, processes are conducted under mild conditions with air as oxidizing agent and water as solvent, and reaction products are environmentally benign because of their biodegradability. In addition oxidized carbohydrate derivatives can often be obtained with high selectivity, and the catalysts are recyclable. These catalytic processes are, therefore, potentially very attractive for the preparation of specialties or intermediates employed in the food, cosmetic, pharmaceutical, and chemical industries. 

The design and synthesis of inexpensive, hydrocarbon based C02-philic materials are of current interest as drey are applicable to the utilization of liquid and supercritical CO2 as an environmentally benign solvent In this section, we describe the molecular interactions involved in enhancing die solubility of carbohydrates in CC>2- We propose the peracetylation of these compounds as a simple method for the preparation of inexpensive, environmentally benign CO2-philes. Utilization of diese materials as COrphiles combines the merits of two important green chemistry principles-environmentally benign solvents and renewable materials. 

The existence of crystalline complexes of cellulose and certain low molecular weight compounds has been known since the 1930 s, and several studies of their structures by X-ray methods have been reported since that time (1-6). These structures are of current relevance In view of the renewed Interest In organic solvents for cellulose In the last 15 years several new solvent systems have been reported. Including dlmethylsulfoxlde-para-f ormaldehyde (7 ), N-methylmorpholine-N-oxlde ( ), hydrazine at elevated temperature and pressure (9 ), and lithium chlorlde-dlmethylacetamlde (10). Analysis of the structure of cellulose solvent complexes provides a detailed molecule model for the polymer solvent Interaction. This paper describes our analyses of the structures of cellulose complexed with ethylenedlamlne, hydrazine, and 1,3-propylenedlamlne. 

Molecular control over EHS as well as performance properties were attained through a design strategy that started with the creation of a chemical library composed of 239 potential solvent candidates. Relevant platform molecnles were selected in order to fulfil a diversity of design criteria inclnding a high renewable atom index, moderate to low vapour pressure and a cost-effective synthetic accessibility (see Table 10.4). 

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