Purification, general procedures with organic

The increased solubility of substituted phthalocyanines (vide infra) enables more common purifications as used for other organic compounds. Usually the purification is done by chromatography either on alumina or silica gel, but recrystallization and extraction procedures can also be used. In some cases, the methods used for unsubstituted phthalocyanines can also be practiced, although the increased molecular weight accompanied by a reduced thermal stability makes sublimation more difficult.97 98 However, for substituted phthalocyanines, the stability towards acid may be reduced97 and, therefore, purification by treatment with sulfuric acid cannot generally be recommended. 

General Procedure for Preparation of Triazones 5a-f. 264 mg (3 mmol) /V,/V-di-metliylurea, 1 g paraformaldehyde, 3 mmol primary amine 4a-f and 2 g montmorillonite K-10 were irradiated by microwave in a Teflon vessel. The reaction mixture was filtered and washed with water. The organic phase was separated and dried with Na2S04 and concentrated by vacuum distillation. Purification of the... 

As was pointed out in Section 2.18, the crude products of most organic reactions are multicomponent mixtures, and a convenient initial isolation procedure, for the first stages of both the separation of such mixtures and of the purification of the components, may involve solvent extraction processes. The general cases which are discussed below to illustrate the technique of solvent extraction are selected to cover many of the commonly met systems. The student is recommended to refer to the comments in Section 2.18 on the necessity of assessing the chemical and physical nature of the components of a particular reaction mixture with regard to their solubilities in solvents, and to their acidic, basic or neutral characteristics. 

A basic difficulty that we find with the LHASA - SECS - REACT strategies is that the reaction paths are more typical of a discrete step-wise laboratory procedure. The use of named organic chemical transforms leads to a bench scale procedure. Reactions of industrial interest on the other hand are generally carried on in one to three continuous steps, with a minimal use of reagents and purification steps. Solid catalyzed vapor or liquid phase reactions are favored. Intermediates and raw materials are far more limited in variety on the scale of industrial production. 

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