Functional group classification tests

Crippen s book (10) gives an extensive compilation of the techniques of organic compound identification with the assistance of GC. It includes a step-by-step account of the preliminary examination, physical property measurements, and functional group classification tests. 

You can see from the preceding analysis how positive and negative information may be utilized in determining the identity of an unknown substance. Of particular note is the importance of the functional group classification tests, which must be done carefully and thoroughly in order to exclude the possible presence of all groups other than the keto group in the unknown. 

An unequivocable identification of an unknown component is unlikely by the chromatographic process alone. Not the least of the reasons for this is the need for the comparisons of standards, thereby assuming reasonable prior assurance of the possible identity of the unknown. Certainly the more discrete pieces of information obtainable concerning an unknown compound, the easier it will be to obtain confident identification. Microchemical tests such as functional group classification, boiling point, elemental analysis, and derivative information, as well as infrared spectroscopy, coulometry, flame photometry, and ultraviolet (UV)-visible spectroscopy are also useful aids when used in conjunction with gas chromatographic data. 

The uses of IR spectra in identification, classification and mechanistic studies have been well documented. Tests for the identification of plastics utilized in Naval ordnance weaponry are discussed in Ref 21. Correlations between polymeric structure and ablative properties using IR spectroscopy have been obtained by monitoring changes in functional group absorption,properties.(Ref 12). The application of IR spectroscopy to the detection of more than 40 of the most common constituents of primers, tracers, igniters, incendiaries,... 

To achieve a detailed classification of the possible interaction of sohd porous non-polar polymeric phases with different functional groups of solute molecules, Gastello and D Amato used the following polarity reference substances ethanol, 2-butanone, nitromethane, benzene, pyridine, w-butanol, 2-pentanone, and 1-nitropropane. The first five represent the test substances proposed by Rohrschneider, while the last three were recommended by McReynolds. The retention indices of these substances enable evaluation of the polarity of any sohd porous polymeric stationary phase. In their studies Porapak Q, as the least polar commercially available porous polymer, was used as the reference stationary phase. 

The solubility tests usually suggest or eliminate several possible functional groups. The chemical classification tests listed in Experiment 52 allow you to distinguish among the possible choices. Choose only those tests that the solubility... 

Although we cannot be complete in this experiment in terms of the functional groups covered or the tests described, the experiment should provide a good introduction to the methods and the techniques chemists use to identify unknown compounds. Textbooks that cover the subject more thoroughly are listed in the References. You are encouraged to consult these for more information, including specific methods and classification tests. 

Functional group analysis using classification tests. 

Classification tests for most of the common functional groups are presented in... 

We repeat the warning given in this section under the heading "Classification Tests" Do not proceed directly to the preparation of a derivative merely on the basis of a hunch about the class of compound to which your unknown belongs. Rather, you should make certain of the type of functional group present... 

Tollens reagent is used as a qualitative test for the presence of the aldehyde functional group (see Chapter 9, Classification Tests). However, benzoin, which does not contain an aldehyde, gives a positive test with this reagent. Explain. 

Chemical Tests. Chemical classification tests (Chapter 9), such as the ignition test and the soda lime test (or sodium fusion test), may also be conducted to further establish the identity of the product. The hydroxamate test may be used to establish the presence of the amide functional group. 

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