Crystallisation primary

The hydrochloride of the amine may be prepared precisely as that of the primary amine. For recrystallisation, boil a suspension of the powdered salt in petroleum (b.p. 60-80°), and then add acetone slowly in small drops until the boiling suspension just becomes clear allow the stirred solution to cool until crystallisation starts, and then chill in ice-water before collecting the colourless plates of the hydrochloride, which after drying in a vacuum desiccator have m.p. 132-134°. 

Mono-substitution products of primary amines cannot easUy be prepared by direct action of the appropriate reagent for example, bromination of aniline yields largely the 2 4 6-tribomo derivative and nitration results in much oxidation. If, however, the amino group is protected as in acetanilide, smooth substitution occurs. Thus with bromine, />-bromoacetanilide is the main product the small quantity of the ortlio isomeride simultaneously formed can be easily eliminated by crystallisation. Hydrolysis of p-bromoacetanilide gives/ -bromoaniline ... 

The experimental conditions necessary for the preparation of a solution of a diazonium salt, diazotisation of a primary amine, are as follows. The amine is dissolved in a suitable volume of water containing 2 5-3 equivalents of hydrochloric acid (or of sulphuric acid) by the application of heat if necessary, and the solution is cooled in ice when the amine hydrochloride (or sulphate) usually crystallises. The temperature is maintained at 0-5°, an aqueous solution of sodium nitrite is added portion-wise until, after allowing 3-4 minutes for reaction, the solution gives an immediate positive test for excess of nitrous acid with an external indicator—moist potassium iodide - starch paper f ... 

Increased pressures can lower the temperature at which crystallisation occurs. Experiments performed using Spectrosil (Thermal Syndicate Ltd.) and G.E. Type 204 (General Electric Company) fused siUcas (see Eig. 2) show that at pressures above 2.5 GPa (<25, 000 atm), devitrification occurs at temperatures as low as 500°C and that at 4 GPa (<40, 000 atm), it occurs at as low as 450°C (107). Although the temperatures and pressures were in the coesite-phase field, both coesite and quarts were observed. Both the devitrification rate and the formation of the stable phase (coesite) were enhanced by the presence of water. In the 1000—1700°C region at 500—4000 MPa (<5, 000-40,000 atm), a- and p-quarts were the primary phases. Crystal growth rates... 

On account of their great lability the diazonium salts of the simple primary amines cannot be isolated from aqueous solution. On the other hand, they crystallise from alcohol when ether is added. Since the metallic salts of nitrous acid are insoluble in alcohol, its esters are used instead for diazotisation in alcohol. These esters are hydrolysed by acid with extraordinary rapidity and therefore behave almost like salts (see p. 147). 

The hydrated salts obtained by ordinary crystallisation from water are relatively unstable, and tend in the solid condition or in aqueous solution with exclusion of air to decompose into thiosulphate and sulphite (the latter as pyrosulphite or acid sulphite, according to the conditions) 3 the further interaction of these primary products complicates the final result. In the case of the sodium salt in aqueous solution the reaction is bimoleeular and follows the scheme 4... 

A major problem, until recently, was the determination of the protein primary structure, but with the advent of modern analysis of DNA this has become comparatively easy. One of the first structures to be described was that of insulin which contains 60 amino-acids and has a molecular weight of 12,000. Once the primary structure is known, it is possible to predict the secondary and tertiary structures using additional information obtained through X-ray crystallography of the crystallised protein. 

The application of Raman spectroscopy in primary manufacturing was reviewed by Fevotte [25] who put a special emphasis on crystallisation monitoring. It includes tables of typical applications in crystallisation monitoring and other transient processes, respectively. The author concludes that several open questions such as better calibration procedures, dependence on size distribution and sampling techniques need to be addressed before we will see a wider use of Raman spectroscopy in pharmaceutical manufacturing applications. Yu et al. [26] presented a broader review of crystallisation control including in-line Raman for polymorph monitoring. The authors discuss future developments needed for the respective techniques and point out the potential of Raman spectroscopy for in-line polymorph detection. 

There is little doubt that the Tuscany mafic magmas have been subject to fractional crystallisation, mixing and crustal assimilation (e.g. Conticelli 1998). However, their high MgO, Ni and Cr concentrations, whose values are close to those of primary mantle melts, exclude that the mafic magmas with different enrichments in potassium and incompatible elements can be derived from each other by any common evolution process. Therefore, it has been concluded that the variable petrological and geochemical compositions of mafic rocks in Tuscany basically result from anomalous and heterogeneous mantle sources (Peccerillo et al. 1987). 

Based on major and trace element variations, it has been argued that fractional crystallisation was the dominant evolutionary mechanism for Ustica magmas (Cinque et al. 1988). The lack of correlation between silica and Sr isotopic ratios has been interpreted as evidence that assimilation of crustal rocks played a minor role during magma evolution. The variable contents of K20, P2Os incompatible elements and radiogenic Sr in the mafic rocks most likely reflect the occurrence of various types of primary melts at Ustica. 

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