Aldehydes, Ketones, Acids, and Esters

Using the double connector C=0 fragment, we can click it to two carbon-based single-connector fragments to form the family of ketones. Acetone is a ketone, and all ketones share the (C)2C=0 unit. 

Acids are typified by their ability to release protons in water solutions. As we explained before in the section on amines, the released protons can be taken up by 

Formic acid Acetic acid (Vinegar) Lactic add 

FIGURE 5.4 Some well-known molecules which are (a) aldehydes and ketones, (b) acids, 

6 Fats (Lipids) Fatty Acids, Prostaglandins, Triglycerides, Cholesterol, Cortisone, etc. 

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In olefines, acetylenes, aldehydes, ketones, acids and esters, etc. if the proton is present in the positive region, it will be shielded and absorption occurs upfield. On the other hand if the proton is in the negative region, its absorption is downfield. 

The gas-phase heats of formation of several enol positive ions of aliphatic aldehydes, ketones, acids, and esters were measured and compared with those of the corresponding keto ions. The enolic ions were found to be thermodynamically more stable by 58-129 kJ moLh This is in marked contrast to the neutral tau-... 

In contrast to phenolic hydroxyl, benzylic hydroxyl is replaced by hydrogen very easily. In catalytic hydrogenation of aromatic aldehydes, ketones, acids and esters it is sometimes difficult to prevent the easy hydrogenolysis of the benzylic alcohols which result from the reduction of the above functions. A catalyst suitable for preventing hydrogenolysis of benzylic hydroxyl is platinized charcoal [28], Other catalysts, especially palladium on charcoal [619], palladium hydride [619], nickel [43], Raney nickel [619] and copper chromite [620], promote hydrogenolysis. In the case of chiral alcohols such as 2-phenyl-2-butanol hydrogenolysis took place with inversion over platinum and palladium, and with retention over Raney nickel (optical purities 59-66%) [619]. 

Abundant sources of terpenoids are the essential oils. They consist of a complex mixture of terpenes or sesquiterpenes, alcohols, aldehydes, ketones, acids and esters [21]. 

Alcohols can be prepared by the hydration of alkenes or by the reduction of aldehydes, ketones, acids, and esters. 

A part of the wood tar is soluble in the distillate formed in the process and is recovered during refining. The heavier portion is separated as an insoluble fraction. The settled tars can be fractionated into light oils consisting of aldehydes, ketones, acids, and esters. Various phenols containing a high proportion of cresols and pitch are present in the heavy tar fraction. 

The reaction yields paraffins, olefins, and oxygenated products such as alcr ols. aldehydes, ketones, acids, and esters. As is usual for an oligomerization, a more or-less complicated product mixture has to be expected rather than the selective formation of individual products. The molecular weight distribution found can be described well by simple equations, originally developed for polymerization processes, considering the probability of chain grouch and chain termination. 

The alkene reduction reactions most frequently observed are of a,3-unsaturated aldehydes, ketones, acids and esters. Examples of stereospecific reductions of acyclic substrates are given in Scheme 50.148.157-159 (j, (, e formation of (123), the double bond of (122) is reduced prior to the aldehyde function. The conversion of (124) to (125) involves oxidation of the intermediate alcohol to the carboxylic acid by bubbling air into the fermentation medium. Stereospecific reductions of a, 3-unsaturated ketones may be similarly effected (Scheme 61). The reduction of the chloro ketone (126) gives (127) initially. This epimerizes under the reaction conditions, and each enantiomer is then reduced further to (128) and (129), with the predominance of the (128) stereoisomer increasing with the size of the R-group. Reduction of ( )-(130) leads to (131) and (132). ... 

The oxidation of alkenes and cycloalkenes may affect the double bonds, the rest of the molecule, or both. Also included in this section are aromatic hydrocarbons containing double bonds in their side chains. Compounds containing double bonds and other functional groups, such as hydroxyl, carbonyl, or carboxyl, will be discussed in the appropriate sections, such as unsaturated alcohols, aldehydes, ketones, acids, and esters. 

Here, the parallels with benzenoid counterparts continue, for these compounds have no special properties - their reactivities are those typical of benzenoid aldehydes, ketones, acids and esters. For example, in contrast to the easy decarboxylation of a-acids observed for pyrrole and furan, thiophene-2-acids do not easily lose carbon dioxide nevertheless, high-temperatme decarboxylations are of preparative value (see also 17.12.1.2). "... 

The carbonyl group (aromatic aldehydes, ketones, acids, and esters) is deactivating and meta directing. There are distinct limitations on the types of substitutions that are satisfactory with carbonyl-substituted aromatics. In general, only those electrophiles in category A in Scheme 9.2 react readily. 

The most common oxygen substitution products of the hydrocarbons to be considered are the alcohols, aldehydes, ketones, acids, and esters. The solubility behavior of these derivatives may be predicted by applying Rulfis I and II. Solubility data for the mono-hydroxy alcohols in water is shown in Table XII. 

Similar considerations hold for aldehydes, ketones, acids, and esters. 

Both alkyl aryl ketones and diaryl ketones can be synthesized using the Friedel-Crafts reaction. However, the method is hmited. Aromatic compounds that have strongly deactivating groups, such as NO2, or carbonyl groups, such as aldehydes, ketones, acids, and esters, do not react. 

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