Organic reactions, involving reactive

Reactions of Alkenes—An Overview Organic Reactions Involving Reactive Intermediates Electrophilic Additions Hydroboration-Oxidation Oxidation... 

The conversion of enol ether 80 to cyclic ketal 83 in water in 12% yield exemplifies the chemoselectivity possible with 14D9.79 Although 83 is the normal product of the acid-catalyzed hydrolysis of 80 in organic solvents, it is never observed in water because the highly reactive oxocarbenium intermediate is rapidly trapped by the solvent to give ketone 82 (via hemiacetal 81) as the sole product. The ability of the antibody to protect the reactive oxonium ion intermediate from hydrolysis and partition it toward a product that is not typically observed under these conditions (i.e., 83) mimics the capabilities of rather sophisticated enzymes. Extension to other reactions involving reactive, water-incompatible intermediates can be easily imagined. 

Many important organic reactions involve carbanions as nucleophiles. The properties of carbanions were introduced in Section 3.4.2, and their reactivity is discussed in more detail in Chapter 6. Most C—H bonds are very weakly acidic and have no tendency to ionize spontaneously to form carbanions. Reactions that involve carbanion intermediates are therefore usually carried out in the presence of a base that can generate the reactive carbanion intermediate. Base-catalyzed addition reactions of carbonyl compounds provide many examples of this type of reaction. The reaction... 

The methyl and ethyl esters of cyanoacetic acid are slightly soluble ia water but are completely miscible ia most common organic solvents including aromatic hydrocarbons. The esters, like the parent acid, are highly reactive, particularly ia reactions involving the central carbon atom however, the esters tend not to decarboxylate. They are prepared by esterification of cyanoacetic acid and are used principally as chemical iatermediates. 

Completion of Esterification. Because the esterification of an alcohol and an organic acid involves a reversible equiUbrium, these reactions usually do not go to completion. Conversions approaching 100% can often be achieved by removing one of the products formed, either the ester or the water, provided the esterification reaction is equiUbrium limited and not rate limited. A variety of distillation methods can be appHed to afford ester and water product removal from the esterification reaction (see Distillation). Other methods such as reactive extraction and reverse osmosis can be used to remove the esterification products to maximize the reaction conversion (38). In general, esterifications are divided into three broad classes, depending on the volatility of the esters ... 

The nature of dangerous reactions involving organic chemicals depends on the saturated, unsaturated or aromatic structures of a particular compound. Saturated hydrocarbons are hardly reactive, especially when they are linear. Branched or cyclic hydrocarbons (especially polycyclic condensed ones) are more reactive, in particular as with oxidation reactions. With ethylenic or acetylenic unsaturated compounds, the products are endothermic . 

Such radicals or ion pairs are formed transiently as reactive intermediates in a very wide variety of organic reactions, as will be shown below. Reactions involving radicals tend to occur in the gas phase and in solution in non-polar solvents, and to be catalysed by light and by the addition of other radicals (p. 300). Reactions involving ionic intermediates take place more readily in solution in polar... 

The use of organic halide to reactivate a decayed catalyst has been known for other catalytic processes involving transition metal catalysts, especially in olefin polymerization reactions (18-21). 

The vast majority of organic radical reactions involve the radical as a reactive intermediate, since their values of k ) are so high, although we need to note that the second reaction need not be particularly fast it only has to be fast in relation to the first reaction. As a good generalization, the intermediate may be treated as a reactive intermediate if k(2)/k r) > 10-3. 

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