Solvent economy

Another aspect of cost reduction would be solvent economy. The need to preferentially select inexpensive solvents and employ the minimum amount of solvent per analysis would be the third performance criteria. Finally, to conserve sample and to have the capability of determining trace contaminants, the fourth criterion would be that the combination of column and detector should provide the maximum possible mass sensitivity and, thus, the minimum amount of sample. The performance criteria are summarized in Table 1. Certain operating limits are inherent in any analytical instrument and these limits will vary with the purpose for which the instrument was designed. For example, the preparative chromatograph will have very different operating characteristics from those of the analytical chromatograph. 

It is seen from equation (18) that the solvent consumption is directly proportional to the charge placed on the column and the capacity ratios of the first peak of the critical pair and the last eluted peak respectively. It is also seen that, as with the optimized analytical column, the diffusivity of the solute and the viscosity of the mobile phase play no part in controlling the solvent economy, it should be pointed out, however, that this is only true for a completely optimized column... 

Employment of potassium cyanate for mechanochemical synthesis of ureas was described by Colacino et al. [30]. Reaction carried out in the planetary mill with KNCO/H2O, without addition of any supplementary base afforded pure phenylalanyl urea 154 in high yield (97%) without need of purification (Scheme 3.43). From an environmental point of view, regarding atom and solvent economy, this procedure for the preparation of urea derivative was very advantageous, hi contrast, an excess of potassium cyanate and heating were necessary to afford phenylalanylurea in solution in 78% yield. 

PFE has been used to extract various additives from different types of polymers, all with good results and the intrinsic advantages of this technique, which include a high throughput, solvent economy, and the production of extracts that require no... 

About 200 ml. of light petroleum is required for recrystallisation. It is therefore advisable, for the sake of economy when the preparation is conducted by a large class of students, that onl about I g. of the crude material be recrystallised from this solvent. The crude compound may be employed in the preparation of p-amino-azobonzene. 

No cresol is obtained if sodium hydroxide alone is used, presumably because the fused sodium hydroxide has no solvent action upon the sodium p-toluene-sulphonate. Potassium hydroxide alone gives excellent results, as do also mixtures of Sodium and potassium hydroxide containing not less than 28 per cent, of potassium hydroxide. The experimental details utilise the minimum amount of potassium hydroxide for the salce of economy. 

Evaporator performance is rated on the basis of steam economy— kilograms of solvent evaporated per kilogram of steam used. Heat is... 

Low-temperature solid-state synthesis is preferred in most cases, where appropriate, for obvious reasons such as energy and cost economy and process safety or for critical concerns regarding the accessibility of compounds that are stable only at low temperatures or non-equilibrium phases, i.e., compounds thermodynamically unstable with respect to the obtained phase (e.g., a ternary instead of binary phase). The use of low-temperature eutectics as solvents for the reactants, hydrothermal growth... 

However, one category of selectivity is largely ignored by organic chemists the atom selectivity , or what is variously called atom economy (Trost, 1991, 1995), atom efficiency, or atom utilization solvents (Sheldon, 1992, 1992a, 1993, 1994, 1996, 1997, 1997a). The complete disregard of this parameter is the root cause of the waste problem in fine chemicals manufacture. 

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