Qualitative organic analysis derivatives

Chapter XI is devoted to Qualitative Organic Analysis. The subject b discussed in moderate detail and this, coupled with the various Sections and Tables of Physical Constants of Organic Compounds and their Derivatives in Chapters III and IV, will provide a satisfactory course of study in this important branch of chemistry. No attempt has been made to deal with Quantitative Organic Analysb in this volume. 

Dinitrophenylhydrazine is used in qualitative organic analysis for preparing solid derivatives of carbonyl compounds. ... 

The classic system of qualitative organic analysis consists of six steps, each of which is discussed in the following subsections. The first four steps, which may be carried out in any order, should be completed before performing the qualitative tests for functional groups. The final step must always be the preparation of one or more solid derivatives. 

Suitable reagents for derivatizing specific functional groups are summarized in Table 8.21. Many of the reactions and reagents are the familiar ones used in qualitative analysis for the characterization of organic compounds by physical means. Alcohols are converted to esters by reaction with an acid chloride in the presence of a base catalyst (e.g., pyridine, tertiary amine, etc). If the alcohol is to be recovered after the separation, then a derivative which is fairly easy to hydrolyze, such as p-nltrophenylcarbonate, is convenient. If the sample contains labile groups, phenylurethane derivatives can be prepared under very mild reaction conditions. Alcohols in aqueous solution can be derivatized with 3,5-dinitrobenzoyl chloride. 

Similarly, there is an increasing degree of consistency of methodological approach between laboratories. For instance, a recent survey of those undertaking qualitative urinary organic acid analysis revealed that more than 90% (83 of 91) of laboratories indicated that they extracted the samples with ethylacetate or ethylacetate/ether, formed trimethylsilyl derivatives and employed gas chromatography-mass spectrometry as a means of analysis. 

Injurious Metals.—These may be derived either from the vessels in which the products are prepared or stored or from mineral colours added to some extent they may be detected in the ash. For a more complete investigation, especially of metals which may be eliminated during the incineration as volatile compounds, use is made of one of the known methods for the destruction of organic substances, e.g., treatment with hydrochloric acid and potassium chlorate, the residue being examined by the ordinary methods of qualitative analysis. 

The preparation of a derivative of a sample compound prior to GC is a significant potential source of both qualitative and, in particular, quantitative errors. Almost all reactions that are used for derivatization are organic syntheses adapted to the micro-scale. This approach makes full use of an advantageous property of GC, namely the need to take only very small amounts of the sample for the analysis, but on the other hand, it makes heavy demands on the quality of the materials used and the precision of the operating procedures. As GC has especially been used in analyses of complex mixtures with large contents of various components, such as biological samples, the operations necessary for the preliminary separation of the compounds of interest from the sample, e.g., extraction or TLC, are often involved in the entire procedure, and make it even more complicated. With some reactions, the necessity for an anhydrous medium requires the application of drying (lyophilization) in the treatment of the sample. 

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