Organic compounds, classification

There are a total of eighteen different hydrocarbon series, of which the most common constituents of crude oil have been presented - the alkanes, cycloalkanes, and the arenes. The more recent classifications of hydrocarbons are based on a division of the hydrocarbons in three main groups alkanes, naphthanes and aromatics, along with the organic compounds containing the non-hydrocarbon atoms of sulphur, nitrogen and oxygen. 

Figure 2-67. Classification of isomeric structures 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. 

There are numerous families of organic compounds, with structures analogous to hydrocarbons, that contain other atoms (e.g., O, N, S, Cl) besides C and H. Classification is done in accordance with the structural theory on the basis of functional groups present. The atom or atomic grouping that characterizes a particular family and also determines the properties of its members is called a Junctional group. Table 2-42 contains a selected list of common functional groups and examples of... 

Carboxylesterases Esterases that hydrolyze organic compounds with carboxylester bonds. Carboxylesterases that are inhibited by organophosphates (OPs) belong to the category EC 3.1.1.1 in the lUB classification of enzymes. 

Scott DR (1995) Empirical pattern recognition/expert system approach for classification and identification of toxic organic compounds from low resolution mass spectra. In Chemometrics in environmental chemistry - applications. Vol 2, part H (Vol ed J Einax), Springer, Berlin Heidelberg New York, p 25... 

Classification of wines according to the grape variety succeeds better, in general, because there are many more typical bouquet components (several hundreds) than mineral and trace elements being typical for the origin of wine. The organic compounds can be analyzed easily and reliably by Headspace Solid-Phase Microextraction Capillary Gas Chromatography and afterwards used for classification (De la Calle et al. [1998]). An example... 

Organic compounds such as the chlorinated solvents also include a wide range of compounds and do not easily fit into the structural classification as described for petroleum hydrocarbons. Chlorinated hydrocarbons are commonly discussed in terms of their relative density (i.e., LNAPL or DNAPL) or degree of halogenation and degree of volatility (i.e., volatile, semi-volatile). 

Kameya T, Murayama T, Kitano M, et al. 1995. Testing and classification methods for the biodegradabilities of organic compounds under anaerobic conditions. Sci Total Environ 170 31-41. 

Scott DR, Dunn WJ III, Emery SL. 1987. Classification and identification of hazardous organic compounds in ambient air by pattern recognition of mass spectral data. Environ Sci Technol 21 891-897. 

Soluble ionic compounds tend to be strong electrolytes, while alcohols and organic compounds are nonelectrolytes. Remember that classification as a strong electrolyte, weak electrolyte, or nonelectrolyte is somewhat subjective. Freshwater can be either a weak electrolyte or a nonelectrolyte depending on its purity. The important consideration in classifying a substance is to what extent an aqueous solution of the substance will conduct electricity. 

In many cases, these polymer chains take on a rod-like (calamitic LCPs) or even disc-like (discotic LCPs) conformation, but this does not affect the overall structural classification scheme. There are many organic compounds, though not polymeric in nature, that exhibit liquid crystallinity and play important roles in biological processes. For example, arteriosclerosis is possibly caused by the formation of a cholesterol containing liquid crystal in the arteries of the heart. Similarly, cell wall membranes are generally considered to have liquid crystalline properties. As interesting as these examples of liquid crystallinity in small, organic compounds are, we must limit the current discussion to polymers only. 

---