Chemical converting unstable into stable compound

Moreover, in terms of the large range of properties of analyzed metabolites, the extraction method is practically useless. Often, it can be replaced or preceded by a derivatization step, as is commonly performed for thiol compounds. These compounds are very unstable but application of an adequate derivatization step converts them into stable derivatives, allowing their determination. Unfortunately, in such a situation, many relevant metabolites are neglected because further analysis is focused only on those that have been subjected to chemical modification. 

When a compound that can form several modifications crystallizes, first a modification may form that is thermodynamically unstable under the given conditions afterwards it converts to the more stable form (Ostwald step rule). Selenium is an example when elemental selenium forms by a chemical reaction in solution, it precipitates in a red modification that consists of Se8 molecules this then converts slowly into the stable, gray form that consists of polymeric chain molecules. Potassium nitrate is another example at room temperature J3-KN03 is stable, but above 128 °C a-KNOs is stable. From an aqueous solution at room temperature a-KN03 crystallizes first, then, after a short while or when triggered by the slightest mechanical stress, it transforms to )3-KN03. 

Numerous investigators subsequently developed the analysis of amino acids, and many different solutions were proposed. The successful solution of this problem is indicative of the efficiency of the application of chemical methods to involatile and unstable complex compounds in order to convert them into substances sufficiently stable to be analysed by GC. 

Trapped by a suitable compound, a transient intermediate can be converted into a more stable species for unequivocal identification. Stepanov and Luzgin (82) investigated the reaction of acetonitrile with 1-octene or tert-butyl alcohol on acidic zeolite HZSM-5 ( 2si/ Ai = 49) at 296 K by in situ MAS NMR spectroscopy under batch reaction conditions. Upon coadsorption of acetonitrile and 1-octene, a C MAS NMR signal at 108 ppm was observed, indicative of TV-alkylnitrilium ions 2 in Scheme 3. As depicted in Scheme 3a, the formation of these cations was explained by trapping the chemically unstable alkylcarbenium ions (formed from the adsorbed... 

---