Eliminations general examples

Generally, MCRs based on aminoazoles and synthetic precursors of a,p-unsaturated carbonyl compounds proceed via a sequence of Knoevenagel-type condensation, which was already mentioned (see Scheme 3), Michael-like addition, cyclization, and water elimination. For example, the authors of [47] considered the following mechanism (Scheme 9). 

Nonionized lipid-soluble drugs are resorbed and not eliminated. Generally, drugs that are bases are excreted when the urine is acidic, whereas acidic compounds are excreted in greater quantities if the urine is alkaline. For example, in phenobarbital (weak acid pKa of 7.3) poisoning, alkalinization of the urine with sodium bicarbonate is helpful in eliminating the phenobarbital. In amphetamine toxicity, acidification of the urine with ammonium chloride is required (Figure 1.13). 

Hydrogen migration with elimination of a neutral alkene molecule accounts for the peak at m/z 92 observed when the alkyl group is longer than C2. Scheme 1.13 illustrates with a general example. Note again that this is an example of a rearrangement. 

On an industrial scale, the elimination generally involves dehydrogenation. For example, styrene, the most important of these compounds—and perhaps the most important synthetic aromatic compound—can be prepared by simply heating ethylbenzene to about 600 in the presence of a catalyst. The ethylbenzene, in... 

E4.18 To get to the general rule, the best guide is to analyse one specific case of bridge formation/water elimination, for example... 

A few general examples show that solvents can be optimized for better performance by mixing. Substantial amounts of solvents can be eliminated by the careful tailoring of the process and properties to the application. Post cleaning with solvent based materials can be minimized or eliminated. 

This process is the reverse of oxidative addition and results when two ligands couple and are eliminated from the metal center with a decrease of two units in the formal oxidation state of the metal. A general example is shown in the following reaction ... 

This preparation was discovered independently by Geuther (1863) and by Frankland and Duppa (1865). The reaction was subsequently investigated in detail and so w idely extended by Claisen that it has become solely a specific example of the more general process known as the Claisen Condensation. Claisen showed that an ester under the influence of sodium ethoxide would not only condense with itself (as in the preparation of ethyl acetoacetate), but also with (i) another ester, (ii) a ketone, if of formula RCHgCOR, (iii) a nitrile, if of formula RCH CN, in each case with the elimination of alcohol. Examples of these modifications are ... 

It is evident that application of Green s theorem cannot eliminate second-order derivatives of the shape functions in the set of working equations of the least-sc[uares scheme. Therefore, direct application of these equations should, in general, be in conjunction with C continuous Hermite elements (Petera and Nassehi, 1993 Petera and Pittman, 1994). However, various techniques are available that make the use of elements in these schemes possible. For example, Bell and Surana (1994) developed a method in which the flow model equations are cast into a set of auxiliary first-order differentia] equations. They used this approach to construct a least-sciuares scheme for non-Newtonian flow equations based on equal-order C° continuous, p-version hierarchical elements. 

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