The Makeup of Organic Compounds

Elemental Composition, Molecular Formula, and Molar Mass 

When describing a compound, we have to specify which elements it contains. This information is given by the elemental composition of the compound. For example, a chlorinated hydrocarbon, as the name implies, consists of chlorine, hydrogen, and carbon. The next question we then have to address is how many atoms of each of these elements are present in one molecule. The answer to that question is given by 

Given the molecular formula, we now have to describe how the different atoms are connected to each other. The description of the exact connection of the various atoms is commonly referred to as the structure of the compound. Depending on the number and types of atoms, there may be many different ways to interconnect a given set of atoms which yield different structures. Such related compounds are referred to as isomers. Furthermore, as we will discuss later, there may be several compounds whose atoms are connected in exactly the same order (i.e., they exhibit the same structure), but their spatial arrangement differs. Such compounds are then called stereoisomers. It should be pointed out, however, that, quite often, and particularly in German-speaking areas, the term structure is also used to denote both the connectivity (i.e., the way the atoms are connected to each other) as well as the spatial arrangement of the atoms. The term constitution of a compound is then sometimes introduced to describe solely the connectivity. 

Electron Shells of Elements Present in Organic Compounds 

Before we can examine how many different structures exist with a given molecular formula (e.g., C4H9C1), we have to recall some of the rules concerning the number and nature of bonds that each of the various elements present in organic molecules may form. To this end, we first examine the electronic characteristics of the atoms involved. 

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GEODE [General Electric organic destruction] A development of the Ultrox process in which a combination of ozone and ultraviolet radiation is used to oxidize traces of organic compounds in water. Developed by the General Electric Company and demonstrated at the Commonwealth Edison nuclear power plant at Dresden, IL, in 1989. The requirement was to reduce the concentration of total organic carbon in the process and makeup waters to the low parts-per-billion range. 

Summary of Biomarker Analyses. The combination of phospholipid fatty acids, steroids, and lignin phenols indicates that the chemical makeup of raw foam includes input from bacterial, algal, diatoms, fungal, and higher plant sources. The total of these compounds account for less than 5% of the organic carbon present in raw foam, and it is not possible, therefore, to assess which is the largest source. These compounds however, do reveal interesting compositional trends between the raw foam and the stream and foam humic substances. The compositional complexity of humic substances increases from stream, to foam, to foam extract and from fulvic acids to humic acids. 

Table 24.4 summarizes the common functional groups, including the C=C and C C groups. Organic compounds commonly contain more than one functional group. Generally, the reactivity of a compound is determined by the number and types of functional groups in its makeup. 

Stereochemistry is one of the most important branches of chemistry. It investigates spatial makeup of chemical compounds, mainly organic, as well... 

Consider azeotropic distillation to dehydrate ethanol with benzene. Initial steady-state conditions are as shown in Fig. 13-108. The overhead vapor is condensed and cooled to 298 K to form two hquid phases that are separated in the decanter. The organic-rich phase is returned to the top tray as reflux together with a portion of the water-rich phase and makeup benzene. The other portion of the water-rich phase is sent to a stripper to recover organic compounds. Ordinarily, vapor from that stripper is condensed and recycled to the decanter, but that coupling is ignored here. 

The reactivity of substituted aromatic compounds, more than that ol any other class of substances, is intimately tied to their exact structure. As a result, aromatic compounds provide an extraordinarily sensitive probe for studying the relationship between structure and reactivity We ll examine that relationship in this and the next chapter, and we ll find that the lessons learned are applicable to all other organic compounds, including such particularly important substances as the nucleic acids that control our genetic makeup. 

Response to organic compounds is proportional to solute mass over seven orders of magnitude. The detection limit is 100 times smaller than that of the thermal conductivity detector (Table 24-5) and is reduced by 50% when N2 carrier gas is used instead of He. For open tubular columns, N2 makeup gas is added to the H2 or He eluate before it enters the detector. The flame ionization detector is sensitive enough for narrow-bore columns. It responds to most hydrocarbons and is insensitive to nonhydrocarbons such as H2, He, N2, 02, CO, C02, H2Q, NH NO, H2S, and SiF4. 

Capillary electrophoresis and mass spectrometry can be coupled using a special ESI interface that provides an additional makeup flow, comprised of water, organic solvent, and acid, to create suitable conditions for ESI (Figure 2.14). Flow rates and sample loading are very low in CE. The supplemental sheath makeup liquid, while useful in the ESI process, has the effect of diluting the analyte, thereby compounding the sensitivity problem caused by the small amounts of analyte used in CE. The importance of CE is that the very large number of theoretical plates available enable complex separations that can reveal subtle differences in analytes. 

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