Organic symbol

Different fields within chemistry have developed their own specialist forms of symbolism. Organic chemistry uses a range of symbols in representations that learners need to make sense of For example, minimal structural representation in organic chemistry (where stractiues may be extensive) uses a formalism that a fine represents two carbon atomic centres joined by a single covalent bond, and saturated with hydrogen except where shown otherwise. 

Fig. 16.6 Reproducibility of the picture forming methods. Fruits from the same sample were analysed twice (before and after storage) and blind coded. The quality-interpretation in the form of a vitality index correlated significantly and well between the two analyses (R2 = 0.72 filled symbols = organic open symbols = conventional same symbol form = same village).

Fig. 16.7 Correlations between the vitality quality index (based on data from picture forming methods and the index of technical quality (based on classical fruit quality tests, see text) in the first year (left) and the second year (right) of the study (filled symbols = organic, open symbols = conventional same symbol form = same village).

Table 5.2 Pathways of organic matter oxidation, hydrogen transformation and fermentation in the sea floor and their standard free energy yields, AG°, per mol of organic carbon. [CH O] symbolizes organic matter of unspecified composition. AG values at pH 7 according to Thauer et al. (1977), Conrad et al. (1986), and Fenchel et al. (1998). (cf Fig. 3.11).

The general formula for such compounds is Ri—O—O—R2, in which Rj and R2 either symbolize organic radicals or an organic radical and hydrogen atom. Organic... 

In the last reaction CH4 symbolizes organic matter in general. 

Figure 7. CHF /CsFe/CaFe at 1000 Torr and 308°K. Key to symbols = organic — nonvolatile inorganic activities A = volatile inorganic activities.

The Wiswesser Line Notation (WLN) was introduced in 1946, in order to organize and to systematically describe the cornucopia of compounds in a more concise manner. A line notation represents a chemical structure by an alphanumeric sequence, which significantly simplifies the processing by the computer [9-11], (n many cases the WLN uses the standard symbols for the chemical elements. Additionally, functional groups, ring systems, positions of ring substituents, and posi-... 

If it be assumed that the ionising characteristics of nitric acid are similar to those of the organic indicators used to define the scales of acidity, then a correspondence between the acidity-dependence of nitration and would suggest the involvement of the nitronium ion, whereas a correspondence with Hq would support the h)rpothesis that the nitric acidium ion were active. The analogies with and Hg are expressed in the first and last pairs of the followii equations respectively. The symbol AQ represents anthraquinone, the indicator originally used in this way for comparison with the acidity dependence of the rate of nitration of nitrobenzene ... 

Here liberties have been taken with the Robinson symbol Instead of restricting its use to a sextet of electrons organic chemists have come to adopt it as an all purpose sym bol for cyclic electron delocalization... 

A number of glossaries of terms and symbols used in the several branches of chemistry have been pubHshed. They include physical chemistry (102), physical—organic chemistry (103), and chemical terminology (other than nomenclature) treated in its entirety (104). lUPAC has also issued recommendations in the fields of analytical chemistry (105), coUoid and surface chemistry (106), ion exchange (107), and spectroscopy (108), among others. 

Figure 24-23 is a sketch of continuous culture with recycle. The symbols for flow rates and organism concentrations are F and X, respec tively Assuming perfect mixing and steady state so that the derivatives can be set to zero, mass balances lead to ... 

Closely related to water solubility as a polarity measure is the partition coefficient of a substance between water and an immiscible organic solvent. Most commonly the organic solvent is selected to be n-octanol, and the symbol P is given to the octanol/water partition coefficient. Then log P is a quantitative measure of hydro-phobicity and, therefore, of nonpolarity. Table 8-3 gives log P values for many of... 

FIGURE 5.8 Two structural motifs that arrange the primary structure of proteins into a higher level of organization predominate in proteins the a-helix and the /3-pleated strand. Atomic representations of these secondary structures are shown here, along with the symbols used by structural chemists to represent them the flat, helical ribbon for the a-helix and the flat, wide arrow for /3-structures. Both of these structures owe their stability to the formation of hydrogen bonds between N—H and 0=C functions along the polypeptide backbone (see Chapter 6). 

To reduce detailed written descriptions on flowsheets, it is usual practice to develop or adopt a set of s) mbols and codes which suit the purpose. Flowsheet symbol standardization has been developed by various professional and technical organizations for their particular fields. Most of these have also been adopted by the American National Standards Institute (ANSI). The following symbol references are related and useful for many chemical and mechanical processes ... 

Li and Hsiao [143] provide a useful approach to the environmental problem of removing (by stripping) volatile organics from solution in a contaminated water stream by using fresh air as the stripping medium. It should be noted that a number of industrial firms perform this stripping with steam. The mass balance on the VOC component around the column (trayed or packed) as shown in Figure 8-55 uses the symbols of Reference 143. 

The symbol R is used in organic chemistry to represent a generalized organic group. The R group can be methyl, ethyl, propyl, or any of a multitude of others. 

The symbol and sign conventions used for substituent effects in this chapter are those most frequently used by writers on correlation analysis in organic chemistry. / or R effects which withdraw electrons from the ring are regarded as positive. See Ref. 48, pp. 229-230 for a more detailed consideration of symbol and sign conventions. 

Organic chemists have found a way to draw complex molecular structures in a very simple way, by not showing the C and H atoms explicitly. A line structure represents a chain of carbon atoms by a zigzag line, where each short line indicates a bond and the end of each line represents a carbon atom. Atoms other than C and H are shown by their symbols. Double bonds are represented by a double line and triple bonds by a triple line. Because carbon almost always forms four bonds in organic compounds, there is no need to show the C—FI bonds explicitly. We just fill in the correct number of hydrogen atoms mentally compare the line structure of 2-chlorobutane, QT3C1TC1CF12C]T3 (3a), with its structural form (3b). Line... 

Let s construct the Lewis structure for the simplest organic molecule, the hydrocarbon methane, CH4. First, we count the valence electrons available from all the atoms in the molecule. For methane, the Lewis symbols of the atoms are... 

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