Greener conventional solvents

Less environmentally-damaging solvents range from wisely-chosen conventional solvents to extremely unconventional solvents. Most of the environmental impact reduction that has been achieved in industry from solvent substitution has been by switching to greener conventional solvents. 

Enzyme biocatalysts were as well tested in neoteric solvents e.g., ionic liquids, supercritical CO, fluorous solvents, and liquid polymers) comparative with conventional solvents e.g., water and organic solvents) in order to achieve a greener biotransformation of the biomass into value-added products [122]. The results provided clear evidences that the enzyme catalyst... 

A side-by-side comparison of the conventional and greener methods illustrates the relatively greater hazards to be confronted if a hostile strike were to provoke uncontrolled release from the conventional factory that relies on mixed solvents (Table 4.2). 

In recent years, the use of heterogeneous catalysis has received useful applications in various organic transformations due to several advantages over conventional homogeneous catalysis. Several solid acid catalysts [108] such as Amberlyst [109], solid-supported fluoroboric acid [110], polyaniline sulfate [111], polystyrene-supported sulfonic acids [112], sulfated zirconia [113], and silica [114] in conjunction with other greener techniques such as MW, US, environmentally benign solvents, solvent-free conditions, and so on have been screened, evaluated, and compared with respect to yields, reaction time, reaction temperature, ease of purification, reusability, toxicity, and other hazards for sustained applications. Many of these efforts have found applications in the medium ring-sized heterocycles such as oxepines, azepines, diazepines, oxazepines, thiazepines, and so on. 

Numerous studies have revealed that biocatalytic reductions can be performed well in the reaction media containing nonaqueous solvents, which vary from conventional organic solvents to greener solvents, such as ionic liquids and supercritical fluids. The use of nonaqueous solvents has not only enhanced the efficiency of bioreductions by allowing the reactions to be conducted at high substrate concentrations, but also altered enzymatic selectivity, including chemo-, regio-and enantioselectivities. 

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