Ethanol, environmentally benign

To pursue the development of environmentally benign synthesis routes for ionic liquids, the alkylation step (Menschutkin reaction) was investigated by the authors in detail. The preparation of the ionic liquid 1-hexyl-3-methyhmidazohum chloride ([CeMlMJCl) was taken as a representative experiment (Scheme 7.2). The process parameters temperature (T = 70-100°C), solvent (ethanol, xylene, cyclohexane, n-heptane, solvent free), concentration of the N-base (c = 1.6-6.7 M), molar ratio n n = 1 0.5-1 4) and reaction time (f = 10-144 h) were investigated. In addition, the N-base was altered in order to proof the transferability of the reaction parameters. 

The first use of supercritical fluid extraction (SFE) as an extraction technique was reported by Zosel [379]. Since then there have been many reports on the use of SFE to extract PCBs, phenols, PAHs, and other organic compounds from particulate matter, soils and sediments [362, 363, 380-389]. The attraction of SFE as an extraction technique is directly related to the unique properties of the supercritical fluid [390]. Supercritical fluids, which have been used, have low viscosities, high diffusion coefficients, and low flammabilities, which are all clearly superior to the organic solvents normally used. Carbon dioxide (C02, [362,363]) is the most common supercritical fluid used for SFE, since it is inexpensive and has a low critical temperature (31.3 °C) and pressure (72.2 bar). Other less commonly used fluids include nitrous oxide (N20), ammonia, fluoro-form, methane, pentane, methanol, ethanol, sulfur hexafluoride (SF6), and dichlorofluoromethane [362, 363, 391]. Most of these fluids are clearly less attractive as solvents in terms of toxicity or as environmentally benign chemicals. Commercial SFE systems are available, but some workers have also made inexpensive modular systems [390]. 

Ethanol is produced as a more environmentally benign fuel. The systematic effect of ethyl alcohol differs from that of methyl alcohol. Ethyl alcohol is rapidly oxidized in the body to carbon dioxide and water, and in contrast to methyl alcohol no cumulative effect occurs. Ethanol is also a preferred alcohol in the transportation sector compared to methanol because it is derived from agricultural products and is renewable and biologically less objectionable in the enviromnent. 

Using an environmentally benign Friedlander synthesis, Yang and co-workers synthesized 11 //-indeno[ l, 2,/)Jquinolincs in refluxing ethanol and a catalytic amount of sodium ethoxide <07T7654>. This method provided a very nice complement to quinoline synthesis through the Friedlander reaction while avoiding harsh reaction conditions. 

The need to address the issue of global warming and fossil resource depletion has prompted research on the sustainable production of environmentally benign fuels and chemicals [ 1]. A biorefinery, which utilizes biomass as the starting material for the production of fuels and chemicals, can not only generate sustainable energy but also reduce CO2 emitted by fossil fuel combustion. For instance, bioethanol is one of the most promising alternatives to conventional petroleum-based transport fuels. The United States produced 52.6 billion liters of ethanol fuel in 2011, an increase from 49.2 billion liters in 2010 [2]. 

Ethyl lactate (ethyl 2-hydroxypropionate) is a nontoxic biodegradable compoxmd naturally found in a variety of food and industrially produced via esterification of lactic acid with ethanol [149]. Both of the components for the production of ethyl lactate are derived from renewable raw material (including low-cost agricultural waste) mainly by the fermentation process. This environmentally benign solvent with high boiling point (154 °C) and low volatility has properties superior to many conventional petroleum-based solvents and can substitute them as an eco-friendly alternative in many reactions [150,151]. The applications of ethyl lactate as a medium for the multicomponent heterocyclic synthesis are exemplified below. 

In the presence of catalytic amounts of vitamin B12, it has been possible to couple 1,1-disubstituted alkenes with defined regiochemistry under mild conditions in environmentally benign solvent system such as ethanol/water (Table 1). The mechanistic studies led the authors to conclude that organic free radicals are formed in this reaction. In the current process, the rate of combination of two radicals is increased by removing the persistent Co(ll) radical with Ti(in) or Zn. This is in contrast to cobalt-catalyzed free-radical chain transfer and cobalt-mediated living radical polymerization in which the cobalt macrocycle s role is to reduce the steady-state concentration of free radicals (Equation (33)). ... 

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