2- pentane 334 COMPOUND INDEX

The 100 Most Important Chemical Compounds focuses on 100 compounds, but references several hundred compounds. Structures and formula for compounds other than the 100 are included in the entries and listed in the index. Repetition of information was kept to a minimum by including representative compounds or the simplest compound in a chemical family and highlighting chemical properties that distinguish chemical groups. For example, there are entries for methane, ethane, butane, and octane but other alkanes such as pentane, hexane, and heptane are not included. Most personal names in the book include years of birth and... 

Capello et al.16 applied LCA to 26 organic solvents (acetic acid, acetone, acetonitrile, butanol, butyl acetate, cyclohexane, cyclohexanone, diethyl ether, dioxane, dimethylformamide, ethanol, ethyl acetate, ethyl benzene, formaldehyde, formic acid, heptane, hexane, methyl ethyl ketone, methanol, methyl acetate, pentane, n- and isopropanol, tetrahydrofuran, toluene, and xylene). They applied the EHS Excel Tool36 to identify potential hazards resulting from the application of these substances. It was used to assess these compounds with respect to nine effect categories release potential, fire/explosion, reaction/decomposition, acute toxicity, irritation, chronic toxicity, persistency, air hazard, and water hazard. For each effect category, an index between zero and one was calculated, resulting in an overall score between zero and nine for each chemical. Figure 18.12 shows the life cycle model used by Capello et al.16... 

It has been shown that the retention behaviour of benzene, butanol, pentan-2-one, nitropropane, and pyridine can be used to classify stationary phases in terms of their polarity (W.O.McReynolds, J. chromatogr. Set., 1970,5,685-691). The retention indices of each of these five reference compounds are measured, first on the stationary phase being tested and then on a standard phase (squalane). The differences in retention index between the two phases (AI) for the five reference compounds are added together to give a constant which is a measure of the polarity of the stationary phase. This constant is known as iheMcReynolds Constant and can be used to compare the ability of stationary phases to separate different classes of compounds (see below). However, this constant gives no information about peak shape, temperature limits, or the suitability for use in capillary colimms. 

The KSF severity index is defined as a logarithmic function of the conversion Xr of a reference hydrocarbon present in the feed. Zdonik selected n-pentane. a compound that is always present in naphthas, and which offers the advantage that it cannot be formed in the pyrolysis of the other components by a side reaction. 

In contrast to these problems, evidence of exposure to pesticides is often much more readily available by analysis of excreta, body fluids and expired air ( ). The power of modern analytical procedures, a topic to be addressed later in this Conference, is exemplified by the characterization of 115 organic compounds in samples of breath from 54 subjects ( ). Exhaled ethane and n-pentane in mice, rats and monkeys (45) has proved to be a useful index of lipid peroxidation, these gases being derived from 0)3-and u)6-fatty acid hydroperoxides (12, 13). Non-invasive measures of drug metabolizing capacity have been developed, using C-phenacetin or C-aminopyrine hepatic dysfunction can be assessed in an analogous manner (, 49). On the horizon is the... 

The test mixture must contain a compound by means of which the breakthrough time can be measured accurately it must be neither retained nor excluded. These conditions are satisfied when the product has a low molar mass and is as closely related to the eluent as possible, e.g. pentane for elution with hexane. Pentane gives no UV absorption but just a small refractive index peak. The plate number cannot be determined from this signal, so another test compound such as toluene or xylene which is rapidly eluted (k 0.2) and which produces a true UV absorption peak is recommended. The theoretical plate number of a little or non-retained substance reflects directly on the packing quality and the extra-column volumes, whereas mass-transfer properties are equally important in peaks that are eluted later. In reversed-phase systems, to can be determined with uracil. The test mixture should also contain compounds for which w 1 and 3-5. 

To some extent, the retention time in a standardized GC analysis can be used for positive identification of the compounds analyzed. The most widely applied approach in this respect is the use of the Kovats retention index (RI) [13], The RI value of a sample peak is determined by comparing its retention time to retention times of closely eluting alkane standards, i.e., the alkanes that elute just before and Just after the sample peak. In this way, the RI is quite insensitive to small changes in experimental conditions. In the Kovats RI system, normal alkanes are assigned an RI value of 100 X the carbon number, e.g., /7-pentane has an RI of 500. In an isothermal separation, the RI of component i with retention time 4,/ (and net retention time of, is thus calculated from... 

Figure X-B-2 shows the representation in CRI-MECH of the initial stages of the oxidation of pentane and its linkage with the oxidation of butane. The figures in brackets refer to the number of C— H and C—C bonds in each compound and, therefore, to the maximum number of ozone molecules that can be generated. Each compound name contains a number, which also refers to the maximum number of ozone molecules that can be formed. Thus, pentane contains 4 C—C bonds and 12 C—H bonds and so has an index of 16, as does the peroxy radical formed by H-abstraction, since it still has the potential to form 16 O3 molecules. The index is reduced by one for the peroxy radical formed by subsequent reaction with NO and then O2, since one NO NO2 conversion has occurred. The labeling of the compounds, e.g., RN1602 and CARB13...

---