THE IDENTIFICATION OF ORGANIC COMPOUNDS

It is essential that students practise these tests until they can be reasonably certain of accurate results with unidentified compounds. The following scheme for the identification of organic compounds is based largely on an initial classification of the compounds according to the elements they contain hence an error in the identification of these elements may lead a student completely astray throughout the subsequent investigation. 

The application of mixed melting point determinations to the identification of organic compounds has been described in Section 1,17. In order to gain experience the student should carry out the following simple experiment. 

NMR IR UVVIS and MS) were obtained using pure substances It is much more common however to encounter an organic substance either formed as the product of a chemical reaction or iso lated from natural sources as but one component of a mixture Just as the last half of the twentieth cen tury saw a revolution in the methods available for the identification of organic compounds so too has it seen remarkable advances in methods for their separation and purification... 

Nuclear magnetic resonance (NMR) is the principal technique for the identification of organic compounds and is among the leading techniques for the determination of their structures. The technique has also been developed, as magnetic resonance imaging (MRI), as a diagnostic procedure in medicine. 

An early field of application in analytical chemistry is structure elucidation. DENDRAL was one of the first ES in general, designed to the identification of organic compounds from mass spectrometric data (Buchanan and Feigenbaum [1978]). In the 1980s and 1990s a flood of expert systems has been developed in analytical chemistry for different types of application, viz ... 

In addition to the use of a melting point determination as a criterion of purity, an equally valuable application is for the identification of organic compounds. If the melting point is known within one degree, the major proportion of possible substances is immediately eliminated from consideration. The study of the general chemical properties of the compound and a mixed melting point determination (Section 1,17) will largely establish the identity of the compound. 

The first edition of this problem-solving textbook was published in 1963 to teach organic chemists how to identify organic compounds from the synergistic information afforded by the combination of mass (MS), infrared (IR), nuclear magnetic resonance (MNR), and ultraviolet (UV) spectra. Essentially, the molecule is perturbed by these energy probes, and the responses are recorded as spectra. UV has other uses, but is now rarely used for the identification of organic compounds. Because of its limitations, we discarded UV in the sixth edition with our explanation. 

The techniques of gas chromatography (GC) and mass spectrometry (MS) have been combined into a powerful instrument, a GC/MS, for the identification of organic compounds. 

The emphasis of this work is on the analysis of plastic additives through gas chromatography/mass spectrometry (GC/MS). GC/MS systems are a common analytical tool in quality control and analytical service laboratories and electron impact (El) mass spectra are recognized as reliable data for the identification of organic compounds. Traditional methods have employed a flame ionization detector (FID) with identifications based solely on GC retention time data. These methods lack the specificity necessary to distinguish between components attributable to the sample matrix or the additive(s). 

In the identification of organic compounds it is generally necessary to transform them into other compounds, the properties of which are determined as an aid in the identification. It often happens that but a few grams of a substance are available for the purpose. The successful handling of such small quantities requires careful work, and the student should have opportunity to learn the special technique required. 

Determination of Specific Gravity.—The determination of specific gravity is often made in the identification of organic compounds. For this purpose results accurate to two units in the third decimal place are sufficient these may be obtained by using as little as 1 cc. of a liquid. A convenient form of apparatus... 

Throughout the laboratory course outlined in the previous chapters, the typical reactions of a number of important classes of compounds have been illustrated by experiments. These reactions are made use of in the identification of organic compounds. Practice in such identifications is of great educational value, as it requires continuous thought on the part of the student, is an excellent review of many facts which have been learned, and has a practical significance. 

The determination of the C H ratio for identification purposes is practicable only if it is performed with a high degree of accuracy. It should be remembered for comparison that the accuracy of classical elemental analysis methods is about 0.3%, which is insufficient for the identification of organic compounds. For example, an absolute error of... 

THE IDENTIFICATION OF ORGANIC COMPOUNDS AND THE DETERMINATION OF THEIR STRUCTURE... 

The main objective of this book is to assist chemists in the identification of organic compounds. The organization of the compounds in classes according to increasing boiling points should also assist in the search for standard vapor phase chromatography work. 

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