Other Mixture-Containing Products

The sources of xenobiotics discussed in the preceding sections are the most prevalent ones. There are numerous others, however. Building materials of construction and furnishings are sources of respiratory, nervous system, and dermal toxins. These are discussed in detail in Chapter 12. Tobacco smoke is responsible for many health effects in man, to both smokers and nonsmokers who are exposed to its toxins. The effects of tobacco smoke are discussed in detail in Chapter 17. 

Air fresheners emit aliphatic and aromatic hydrocarbons, ethyl butyrate, /n-methoxybenzaldehyde TV-methylformamide, and other compounds that together are pulmonary irritants and induce behavioral abnormalitiesJ48  

Mattress covers emit mixtures of aromatic hydrocarbons, TCE, and phenol, the mixture of which induces acute respiratory effects including asthma-like reactionsJ49l Similar effects are observed with emissions from disposable diapers. I50 though such responses are not predicted from the measured concentrations of the chemicals. 

Exposures to single toxic chemicals in and around the house produce many well-known identifiable effects in people. An example of such an effect is respiratory irritation following inhalation of chlorine bleach fumes. Often, individuals develop clinical symptoms that are associated with mixtures of chemicals, for example, headache and dizziness following inhalation of paint fumes containing toluene and glycol ethers. 

At times, people react acutely or chronically to unknown stimulants. In such cases, it is hypothesized that unidentified mixtures are often the causative agents. Such toxic mixtures can arise from mixtures of two or more household products as well as from the mixture of household chemicals with chemicals from foods, outdoor air pollutants, water pollutants, or industrial chemicals that are carried into the home on the clothing of workers. In many of these mixture exposure instances, the health effects cannot be attributed to any of the individual chemicals present, but produce distinct clinically defined symptoms. 

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Concretes and absolutes, both obtained by total extraction of the plant material and not subject to any form of distillation other than solvent removal, are complex mixtures containing many chemical types over wide molecular weight ranges. In some cases, gas chromatographic analysis shows httle volatile material. Yet these products have powerful odors and contribute in important ways to the perfumes in which they are used. 

Chlorination with Other Reagents. Chlorotoluenes can also be obtained in good yields by the reaction of toluene with stoichiometric proportions of certain Lewis acid chlorides such as inon(III) chloride, as the chlorinating agent (51). Generally, the product mixture contains /)-chlorotoluene as the principal component. Several modifications have been proposed to improve product yields (52,53). 

When a mixture is cracked, one or more components in the feed may also be formed as products. Eor example, in the cocracking of ethane and propane, ethane is formed as a product of propane cracking and propane is formed as a product of ethane cracking. Therefore, the "out" term in the above equation contains the contribution or formation from other feed components and hence does not represent tme conversion. Eor simple mixtures, the product formation can be accounted for, and approximate tme conversions can be calculated (29). Eor Hquid feeds like naphtha, it is impractical if not impossible to calculate the tme conversion. Based on measured feed components, one can calculate a weighted average conversion (A) (30) ... 

There are some indications that the situation described above has been realized, at least partially, in the system styrene-methyl methacrylate polymerized by metallic lithium.29 29b It is known51 that in a 50-50 mixture of styrene and methyl methacrylate radical polymerization yields a product of approximately the same composition as the feed. On the other hand, a product containing only a few per cent of styrene is formed in a polymerization proceeding by an anionic mechanism. Since the polymer obtained in the 50-50 mixture of styrene and methyl methacrylate polymerized with metallic lithium had apparently an intermediate composition, it has been suggested that this is a block polymer obtained in a reaction discussed above. Further evidence favoring this mechanism is provided by the fact that under identical conditions only pure poly-methyl methacrylate is formed if the polymerization is initiated by butyl lithium and not by lithium dispersion. This proves that incorporation of styrene is due to a different initiation and not propagation. 

Since many years, pectolytic enzymes have been widely used in industrial beverage processing to improve either the quality and the yields in fruit juice extraction or the characteristics of the final product [1,2]. To this purpose, complex enzymatic mixtures, containing several pectolytic enzymes and often also cellulose, hemicellulose and ligninolytic activities, are usually employed in the free form. The interactions among enzymes, substrates and other components of fruit juice make the system very difficult to be investigated and only few publications are devoted to the study of enzymatic pools [3-5], An effective alternative way to carry out the depectinisation process is represented by the use of immobilized enzymes. This approach allows for a facile and efficient enzymatic reaction control to be achieved. In fact, it is possible to avoid or at least to reduce the level of extraneous substances originating from the raw pectinases in the final product. In addition, continuous processes can be set up. 

The molar ratio of these compounds was approximately 3 2. They could not be transformed into each other, and separation of the isomers has not yet been successful. Evidently, the initial product mixture, containing phosphorus-rich polycyclic compounds, was degraded into the bicyclic 48 and 49. Similar product mixtures, for which structures have been established, were also observed by the analogous transformation of ( > 1,2-di-re rf-butyl- 1,2-dimesityldisilene and tetramesityldisilene with white phosphorus and yellow arsenic (As4), respectively.46... 

As noted above, whole-cell MALDI-TOF MS was intended for rapid taxonomic identification of bacteria. Neither the analysis of specific targeted bacterial proteins, nor the discovery of new proteins, was envisioned as a routine application for which whole cells would be used. An unknown or target protein might not have the abundance or proton affinity to facilitate its detection from such a complex mixture containing literally thousands of other proteins. Thus, for many applications, the analysis of proteins from chromatographically separated fractions remains a more productive approach. From a historical perspective, whole-cell MALDI is a logical extension of MALDI analysis of isolated cellular proteins. After all, purified proteins can be obtained from bacteria after different levels of purification. Differences in method often reflect how much purification is done prior to analysis. With whole-cell MALDI the answer is literally none. Some methods attempt to combine the benefits of the rapid whole cell approach with a minimal level of sample preparation, often based on the analysis of crude fractions rather... 

Approaches to the determination of the concentration-dependent terms in expressions for reversible reactions are often based on a simplification of the expression to limiting cases. By starting with a mixture containing reactants alone and terminating the study while the reaction system is still very far from equilibrium, one may use an initial rate study to determine the concentration dependence of the forward reaction. In similar fashion one may start with mixtures containing only the reaction products and use the initial rates of the reverse reaction to determine the concentration dependence of this part of the rate expression. Additional simplifications in these initial rate studies may arise from the use of stoichiometric ratios of reactants and/or products. At other times the use of a vast... 

Diels-Alder cycloadditions of sila- and germa[3]radialenes 541 with MTAD or PTAD provide the corresponding products 542 (Equation 73) <19930M1996, 1994AG723>. Similarly, phospha derivative 543 with MTAD gives 544 (Equation 74). On the other hand, the same reaction of cyclic 545 with MTAD is slower and the formed reaction mixture contains only small amount of a product probably analogous to 544 and compound 546 as the major product (Equation 75) <2000JA12507>. 

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