Alternative green reagent

Industry, in fact, has a major interest in these diesters as building blocks for nylon 6,6 and nylon 7,7 in the production of polyesters and polyamides. However, their present synthesis raises an environmental concern. For instance, the oxidation of cyclohexanone by nitric acid (for the preparation of adipic acid), accounts for more than 10% of the total yearly release of N2O, which is among the main gases responsible for the greenhouse effect. The reaction of Scheme 4.14 represents an eco-friendly alternative synthesis of a,(i)-diesters which uses green reagents and, relevantly, has a 100% atom economy. The overall process is mechanistically described as a retro-Claisen condensation. 

Additionally, the environmental issue of utilizing waste cellulosic material and waste biomass products should be considered as an alternative green chemistry application to the production of many value added products. The combinatorial utilization of carbohydrate scaffolds based on chiral building block functionalization will also constitute attractive and relatively cheap starting materials. This rich selection of potential approaches, combined with further developments of new procedures and modem reagents, creates an enormous opportunity for the field to be at the frontier for many years to come. 

To this purpose, dimethyl carbonate (DMC) can be used as a transesterification reagent for making esters from lipids, which directly achieves alternative soluble co-products in the biodiesel solutions. The reaction is rather attractive, as DMC is reputed to be the prototype of green reagents due to its health and environmental inertness (Li et al., 2005). Therefore, a fuel produced using DMC and vegetable oils or animal fats as raw materials must be considered as an alternative fuel fully derived from renewable resources. Thus, DMC operates as an alternative acyl acceptor, which is neutral, cheap, and non toxic. 

Nitrates. Iron(II) nitrate hexahydrate [14013-86-6], Fe(N03)2 6H20, is a green crystalline material prepared by dissolving iron in cold nitric acid that has a specific gravity of less than 1.034 g/cm. Use of denser, more concentrated acid leads to oxidation to iron(III). An alternative method of preparation is the reaction of iron(II) sulfate and barium or lead nitrate. The compound is very soluble in water. Crystallisation at temperatures below — 12°C affords an nonahydrate. Iron(II) nitrate is a useful reagent for the synthesis of other iron-containing compounds and is used as a catalyst for reduction reactions. 

Overall, green solvents appear to be a valuable alternative to conventional solvents in addition reactions of diverse organozinc reagents to aldehydes. 

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